2024/02/01 更新

写真a

フジイ タツオ
藤井 達生
FUJII Tatsuo
所属
環境生命自然科学学域 教授
職名
教授
外部リンク

学位

  • 理学博士 ( 京都大学 )

研究キーワード

  • 誘電体

  • フェライト

  • 磁性体

  • Photoelectron spectroscopy

  • 遷移金属酸化物

  • Magnetic materials

  • Mossbauer spectroscopy

  • Ceramics

  • Ferrites

  • Thin films

  • Transition metal oxides

  • 光電子分光

  • メスバウアー分光

  • 高周波材料

  • X線分光

研究分野

  • ナノテク・材料 / 無機材料、物性

  • ナノテク・材料 / 機能物性化学

 

論文

  • Influence of viscosity and composition of alkali borosilicate lead-free frit on its reaction with hematite, and the color control of red overglaze enamels

    Misa Ogawa, Yuuka Kokubo, Yuto Okawara, Hirofumi Inada, Taigo Takaishi, Tatsuo Fujii, Toshinori Okura, Hideki Hashimoto

    Journal of the European Ceramic Society   43 ( 15 )   7205 - 7214   2023年12月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.jeurceramsoc.2023.07.035

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  • c軸成長した針状六方晶フェライト粒子の合成への試み 査読

    西岡 栞平, 山本 悠, 高橋 勝國, 狩野 旬, 藤井 達生

    粉体および粉末冶金   70 ( 9 )   398 - 401   2023年9月

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    担当区分:責任著者   記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.2497/jjspm.23-00019

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  • Co-substituted Ca–La magnetoplumbite ferrite microwave absorbers at 100 GHz

    Kazushige Hyodo, Jun Kano, Makoto Nakanishi, Tatsuo Fujii

    Applied Physics Letters   122 ( 11 )   2023年3月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:AIP Publishing  

    Millimeter wave absorption exceeding 70 GHz has been performed in a Co-substituted Ca–La magnetoplumbite (M-type) ferrite. A polymerized complex method was used to increase the substitution of La and Co ions in the M-type ferrite. The increase in the magnetic anisotropy field combined with the remaining significant saturation magnetization results in good magnetic resonance absorption in the millimeter range of 70–100 GHz. Above 70 GHz, good millimeter wave absorption of more than −20 dB was achieved in 0.25 mm thickness plates of Ca0.46La0.54Fe11Co0.28O19-η and Ca0.42La0.58Fe11Co0.58O19-η. Highly Co-substituted Ca–La M-type ferrites may, thus, be promising candidates for magnetic absorption materials operating in frequencies of up to 100 GHz.

    DOI: 10.1063/5.0133578

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  • Nonlinear Optical Properties in an Epitaxial YbFe2O4 Film Probed by Second Harmonic and Terahertz Generation

    Hongwu Yu, Yoichi Okimoto, Atsuya Morita, Shuhei Shimanuki, Kou Takubo, Tadahiko Ishikawa, Shin-ya Koshihara, Ryusei Minakami, Hirotake Itoh, Shinichiro Iwai, Naoshi Ikeda, Takumi Sakagami, Mayu Nozaki, Tatsuo Fujii

    Materials   16 ( 5 )   1989 - 1989   2023年2月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI AG  

    An epitaxial film of YbFe2O4, a candidate for oxide electronic ferroelectrics, was fabricated on yttrium-stabilized zirconia (YSZ) substrate by magnetron sputtering technique. For the film, second harmonic generation (SHG), and a terahertz radiation signal were observed at room temperature, confirming a polar structure of the film. The azimuth angle dependence of SHG shows four leaves-like profiles and is almost identical to that in a bulk single crystal. Based on tensor analyses of the SHG profiles, we could reveal the polarization structure and the relationship between the film structure of YbFe2O4 and the crystal axes of the YSZ substrate. The observed terahertz pulse showed anisotropic polarization dependence consistent with the SHG measurement, and the intensity of the emitted terahertz pulse reached about 9.2% of that emitted from ZnTe, a typical nonlinear crystal, implying that YbFe2O4 can be applied as a terahertz wave generator in which the direction of the electric field can be easily switched.

    DOI: 10.3390/ma16051989

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  • Uniform Formation of a Characteristic Nanocomposite Structure of Biogenous Iron Oxide for High Rate Performance as the Anode of Lithium-Ion Batteries

    Masakuni Takahashi, Ryo Sakuma, Hideki Hashimoto, Tatsuo Fujii, Jun Takada

    JOURNAL OF PHYSICAL CHEMISTRY C   2223 - 2230   2023年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    Recently, Fe2O3 has been considered as an alternative anode material for lithium-ion batteries (LIBs) owing to its high theoretical capacity (approximately 1000 mA h g-1), low cost, and nontoxicity. However, its rate performance remains poor relative to that of the conventional graphite anode. In this study, Fe2O3-based anodes were prepared through the annealing of biogenous Fe2O3 (L-BIOX) samples produced by an aquatic Fe-oxidizing bacterium. The effect of the annealing temperature on the performance of the synthesized Fe2O3-based material as the anode of an LIB was investigated. Electrochemical measurements revealed that the annealed L-BIOX samples at 300-700 degrees C exhibited higher rate performances than the unannealed material. Particularly, the sample annealed at 700 degrees C exhibited the highest capacity among the synthesized materials and showed a higher performance than the previously reported Fe2O3-based anodes. It exhibited a capacity of 923 mA h g-1 even at a high current density of 2 A g-1. After annealing at 700 degrees C and discharging, the synthesized biogenous material had a uniform nanocomposite structure composed of alpha-Fe2O3 nanoparticles dispersed in an amorphous matrix of Li-Si-P oxide. To form this uniform nanostructure, the solid-state diffusion resistance of the Li+ ions in the active material was reduced, which consequently improved the rate performance of the electrode. Therefore, this study provides substantial insights into the development and improvement of the performance of novel Fe2O3-based nanomaterials as the anode of LIBs.

    DOI: 10.1021/acs.jpcc.2c08380

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  • Spinodal Decomposition in the Mg–Al–Fe–O System 査読

    Yoshihiro Kusano, Taiki Furuta, Ryosuke Maki, Tomoyuki Ogawa, Tatsuo Fujii

    Inorganic Chemistry   61 ( 45 )   18170 - 18180   2022年11月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:American Chemical Society (ACS)  

    DOI: 10.1021/acs.inorgchem.2c02843

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  • Eco-Benign Orange-Hued Pigment Derived from Aluminum-Enriched Biogenous Iron Oxide Sheaths. 査読 国際誌

    Katsunori Tamura, Yuri Oshima, Yuta Fuse, Noriyuki Nagaoka, Tatsuki Kunoh, Makoto Nakanishi, Tatsuo Fujii, Tokuro Nanba, Jun Takada

    ACS omega   7 ( 15 )   12795 - 12802   2022年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Inorganic pigments have been widely used due to their low cost of production, strong hiding power, and chemical resistance; nevertheless, they have limited hue width and chromaticity. To eliminate these disadvantages, we herein propose the use of an ingenious biotemplate technique to produce Al-enriched biogenic iron oxide (BIOX) materials. Spectrophotometric color analysis showed that high levels of Al inclusion on heat-treated BIOX samples produced heightened yellowish hues and lightness. The Al-enriched BIOX sheaths exhibited a stable tubular structure and excellent thermal stability of color tones after heating at high temperatures and repetitive heat treatments. Ultrastructural analysis and mechanical destruction experiments revealed that the highly chromatic orange-hue of these pigments are ascribed probably to an ingenious cylindrical nanocomposite architecture composed of putative Fe-included low crystalline Al oxide regions and hematite particles embedded therein. The present work therefore demonstrates that the bioengineered material can serve as an epochal orange-hued inorganic pigment with low toxicity and marked thermostability that should meet large industrial demand.

    DOI: 10.1021/acsomega.1c07390

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  • Valence control of charge and orbital frustrated system YbFe<inf>2</inf>O<inf>4</inf> with electrochemical Li+ intercalation 査読

    S. Murase, Y. Yoshikawa, K. Fujiwara, Y. Fukada, T. Teranishi, J. Kano, T. Fujii, Y. Inada, M. Katayama, K. Yoshii, T. Tsuji, D. Matsumura, N. Ikeda

    Journal of Physics and Chemistry of Solids   162   110468   2022年3月

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    掲載種別:研究論文(学術雑誌)  

    We report an attempt valence control of the mixed valence iron triangular oxide YbFe2O4 to develop an effective technique controling the frustration of charges in strongly correlated electron systems. The electrochemical doping of Li + into YbFe2O4 was examined on a cell-type sample similar to the Li-ion secondary battery cell. Systematic changes in the lattice constant and Fe – Fe and Fe–Yb distance were observed with Li doping. Maximum value of the doping was over 300 mAh/g. An EXAFS experiment indicated that Li positioned between Yb octahedron layer (U-layer) and Fe-bipyramidal layer (W-layer). However, detailed change of iron valence state of YbFe2O4was not clearly observed because of the superimpose of the signal from iron metal nano particles in XANES observation. We discuss that the uncertainty might arise from the inhomogeneous distribution of the sample particle size, which might prevent the homogeneous doping of Li because the doping occurs on the surface of each nano-particles.

    DOI: 10.1016/j.jpcs.2021.110468

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  • High valence states of Pd supported on ferroelectric BaTiO3 driven by electric polarization

    Tasuku Yoshida, Jun Kano, Masaichiro Mizumaki, Yusuke Tamenori, Kiyofumi Nitta, Kazuo Kato, Satoshi Hinokuma, Norihiro Oshime, Satoshi Hirose, Hitoshi Mikami, Naoshi Ikeda, Tatsuo Fujii, Yuta Nishina, Tomoko Okubo

    Applied Physics Letters   119 ( 9 )   092904 - 092904   2021年8月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:AIP Publishing  

    DOI: 10.1063/5.0066289

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  • Single domain growth and charge ordering of epitaxial YbFe2O4 films

    Takumi Sakagami, Reika Ota, Jun Kano, Naoshi Ikeda, Tatsuo Fujii

    CRYSTENGCOMM   2021年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    YbFe<INF>2</INF>O<INF>4</INF> is a charge-ordered ferroelectric that exhibits coupling between magnetization and electric polarization near room temperature and crystallizes in a rhombohedral structure (R3m). This study presents an attempt to fabricate stoichiometric and epitaxial YbFe<INF>2</INF>O<INF>4-delta</INF> films with a nearly single-domain structure using an RF magnetron sputtering method. The (0001)-oriented epitaxial films of YbFe<INF>2</INF>O<INF>4-delta</INF> on YSZ (111) substrates via reactive sputtering method exhibited clear three-fold symmetry normal to the substrate without the formation of twin domains rotated by 60 degrees. The oxygen stoichiometry of the epitaxial YbFe<INF>2</INF>O<INF>4-delta</INF> was improved by controlling an oxygen partial pressure (P<INF>O<INF>2</INF></INF>) during the deposition. The films showed a sharp ferrimagnetic transition, and the transition temperature (T<INF>N</INF>) increased linearly to approximately 245 K with decreasing P<INF>O<INF>2</INF></INF>. The magnitude of magnetization of the obtained films was comparable to that of bulk single crystals. Further, the electron diffraction pattern of the stoichiometric films confirmed the presence of three-dimensional charge order, which is consistent with the behavior of the bulk crystals as well.

    DOI: 10.1039/d1ce00834j

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  • Light reflectance and photoelectron yield spectroscopy enable acceptor level measurement in p-type Ba1-xTiO3 semiconductor

    Saya Fujii, Jun Kano, Norihiro Oshime, Tohru Higuchi, Yuta Nishina, Tatsuo Fujii, Naoshi Ikeda, Hiromi Ota

    JOURNAL OF APPLIED PHYSICS   129 ( 8 )   2021年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    We report the band structure of Ba-deficient BaTiO3 as a p-type semiconductor, studied by a combination of light reflectance and photoelectron yield spectroscopy. Two acceptor levels were observed at the tail of a valence band. As the quantity of Ba vacancies increased, the density of state of the two acceptor levels also increased. The levels of the conduction band minimum and the valence band maximum shifted far away from the vacuum level, but the bandgap seems to be independent of Ba deficient concentration. For classical semiconductors such as Si and GaAs, the observation of impurity levels is restricted to low temperatures (similar to 20K) owing to their narrow bandgaps. Oxide semiconductors have now been demonstrated with wide bandgaps and acceptor levels, at normal operating temperatures, which could lead to new device designs in the future.

    DOI: 10.1063/5.0033761

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  • Chemical reaction between lead-free multicomponent alkali borosilicate glass frit and hematite during heat treatment

    Hideki Hashimoto, Akane Terasawa, Hirofumi Inada, Taigo Takaishi, Tatsuo Fujii, Hidetaka Asoh

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   41 ( 1 )   823 - 830   2021年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    A mixture of a lead-free multicomponent alkali borosilicate glass frit containing zinc ions and hematite was heat-treated under various conditions to elucidate the reaction between the two components, which is essentially important for controlling the color of red overglaze enamels. Above the glass transition temperature, the interaction between the frit fluid and hematite was evident, as the viscosity of the frit decreased. Moreover, hematite dissolved, the iron ions diffused into the glass matrix and they precipitated on residual hematite, resulting in enhanced crystal growth through Ostwald ripening. Concurrently, the iron and zinc ions reacted to form zinc ferrite. During cooling, the supersaturated iron ions were consumed for precipitation of hematite and zinc ferrite. Because frit and hematite dramatically react during heat treatment, conventional modification of hematite alone is insufficient. Development of the frit exhibiting low reactivity toward hematite through precise control of physical properties is a future challenging issue.

    DOI: 10.1016/j.jeurceramsoc.2020.08.037

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  • Skewed electronic band structure induced by electric polarization in ferroelectric BaTiO3

    Norihiro Oshime, Jun Kano, Eiji Ikenaga, Shintaro Yasui, Yosuke Hamasaki, Sou Yasuhara, Satoshi Hinokuma, Naoshi Ikeda, Pierre-Eymeric Janolin, Jean-Michel Kiat, Mitsuru Itoh, Takayoshi Yokoya, Tatsuo Fujii, Akira Yasui, Hitoshi Osawa

    SCIENTIFIC REPORTS   10 ( 1 )   2020年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATURE RESEARCH  

    Skewed band structures have been empirically described in ferroelectric materials to explain the functioning of recently developed ferroelectric tunneling junction (FTJs). Nonvolatile ferroelectric random access memory (FeRAM) and the artificial neural network device based on the FTJ system are rapidly developing. However, because the actual ferroelectric band structure has not been elucidated, precise designing of devices has to be advanced through appropriate heuristics. Here, we perform angle-resolved hard X-ray photoemission spectroscopy of ferroelectric BaTiO3 thin films for the direct observation of ferroelectric band skewing structure as the depth profiles of atomic orbitals. The depth-resolved electronic band structure consists of three depth regions: a potential slope along the electric polarization in the core, the surface and interface exhibiting slight changes. We also demonstrate that the direction of the energy shift is controlled by the polarization reversal. In the ferroelectric skewed band structure, we found that the difference in energy shifts of the atomic orbitals is correlated with the atomic configuration of the soft phonon mode reflecting the Born effective charges. These findings lead to a better understanding of the origin of electric polarization.

    DOI: 10.1038/s41598-020-67651-w

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  • Bright Yellowish-Red Pigment Based on Hematite/Alumina Composites with a Unique Porous Disk-like Structure

    Hideki Hashimoto, Jun Kiyohara, Arisa Isozaki, Yuya Arakawa, Tatsuo Fujii, Jun Takada, Hirofumi Inada, Taigo Takaishi, Hidetaka Asoh

    ACS OMEGA   5 ( 8 )   4330 - 4337   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    Inspired by a bacteriogenic, iron-based oxide material and a traditional Japanese red pigment, a bright yellowish-red pigment was prepared by heating an Al-containing iron oxyhydroxide precursor. The obtained red pigment had a unique porous disk-like structure, comprising Al-substituted hematite particles and crystalline alumina nanoparticles. Although these disk-like structures loosely gathered to form an aggregate in powder, they can be easily dispersed into a single, disk-like structure by simple ultrasonic irradiation. The powder exhibited a bright yellowish-red color and high thermostability, making it attractive as a coloring material for various industrial products needing a bright-red color, high weather resistance, and durability. Quantitative color measurements revealed extremely high L*, a*, and b* values that are much greater than those of commercially available hematite. The thermostability test showed that even after exposure to high temperatures, the pigment retained the red color, indicating its high thermostability. The unique microstructure should be strongly related to the bright yellowish-red color and the high thermostability of the developed red pigment.

    DOI: 10.1021/acsomega.9b04297

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  • Intermittent parathyroid hormone 1–34 induces oxidation and deterioration of mineral and collagen quality in newly formed mandibular bone 査読

    Yohsuke Yoshioka, Eiki Yamachika, Makoto Nakanishi, Tadashi Ninomiya, Sho Akashi, Sei Kondo, Norifumi Moritani, Yasuhiro Kobayashi, Tatsuo Fujii, Seiji Iida

    Scientific Reports   9 ( 1 )   8041   2019年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Science and Business Media LLC  

    Abstract

    Intermittent parathyroid hormone (PTH) administration is known to promote bone healing after surgical procedures. However, the mechanism and influence of PTH on the mineral and collagen quality of the jaw are not well understood. Most studies have focused on analyzing the bone density and microstructure of the mandible, and have insufficiently investigated its mineral and collagen quality. Oxidative stress activates osteoclasts, produces advanced glycation end products, and worsens mineral and collagen quality. We hypothesized that PTH induces oxidation and affects the mineral and collagen quality of newly formed mandibular bone. To test this, we examined the mineral and collagen quality of newly formed mandibular bone in rats administered PTH, and analyzed serum after intermittent PTH administration to examine the degree of oxidation. PTH administration reduced mineralization and worsened mineral and collagen quality in newly formed bone. In addition, total anti-oxidant capacity in serum was significantly decreased and the oxidative-INDEX was increased among PTH-treated compared to vehicle-treated rats, indicating serum oxidation. In conclusion, intermittent administration of PTH reduced mineral and collagen quality in newly formed mandibular bone. This effect may have been induced by oxidation.

    DOI: 10.1038/s41598-019-44389-8

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    その他リンク: http://www.nature.com/articles/s41598-019-44389-8

  • 青色無機顔料コバルトブルーの色調におよぼすコバルト原料化合物の影響 査読

    米田 美佳, 辰己 祐哉, 三野 泰志, 中曽 浩一, 後藤 邦彰, 中西 真, 藤井 達生, 小西 康裕, 野村 俊之

    粉体工学会誌   56 ( 8 )   446 - 451   2019年8月

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  • In situ Mossbauer analysis of bacterial iron-oxide nano-particles for lithium-ion battery

    Ryo Sakuma, Hideki Hashimoto, Tatsuo Fujii, Jun Takada, Naoaki Hayashi, Mikio Takano

    HYPERFINE INTERACTIONS   240 ( 1 )   2019年8月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPRINGER INTERNATIONAL PUBLISHING AG  

    Nanometric amorphous iron-based oxides of bacterial origin show a great potential as an Fe3+/Fe-0 conversion anode material for lithium-ion batteries. By means of in situ Mossbauer spectroscopy, chemical states of Fe ions were examined under the discharge-charge process of the bacterial iron-oxide electrode in a lithium-ion half-cell. As for the first discharge process, the successive reduction of Fe3+-> Fe2+-> Fe-0 occurred in the electrode as a function of the cell voltage. While on the charge process, Fe-0 in the electrode was oxidized directly to Fe3+ without going through Fe2+.

    DOI: 10.1007/s10751-019-1639-y

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  • Solid-state synthesis and characterization of cobalt blue core-shell pigment particles

    Mika Yoneda, Kuniaki Gotoh, Makoto Nakanishi, Tatsuo Fujii, Yasuhiro Konishi, Toshiyuki Nomura

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   102 ( 6 )   3468 - 3476   2019年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY  

    Cobalt blue is one of the most chemically and thermally stable blue pigments. However, cobalt is scarce and expensive. To minimize the use of cobalt and reduce production costs and toxicity, cobalt blue core-shell pigments were synthesized by a solid-state method, which is cheaper than a liquid-phase reaction. Small cobalt hydroxide particles and large -alumina particles, in various ratios, were used as the starting materials. The dry mixed powders were calcined at 1200 degrees C for 2hours. Elemental mappings of the surfaces and cross sections of the synthesized particles showed that the cobalt blue had a core-shell structure. X-ray diffraction patterns showed that the synthesized cobalt blue consisted of an -alumina core and a cobalt aluminate shell. The color tone of the synthesized cobalt blue was evaluated from the lightness (L*) and chroma (C*) values. The color tone of the cobalt blue synthesized in this study was almost same as those of commercially available samples although the cobalt molar fraction was lower than the stoichiometric ratio (Co/(Co+Al)=0.33, Co/Al=0.5) which was calculated from the chemical reaction formula.

    DOI: 10.1111/jace.16191

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  • Bright greenish-yellow pigments based on Sc<inf>2−</inf><inf>x</inf>Fe<inf>x</inf>O<inf>3</inf> solid solutions with bixbyite structure

    Hideki Hashimoto, Kotaro Sayo, Hidetaka Asoh, Tatsuo Fujii, Mikio Takano, Atsunobu Masuno, Atsunobu Masuno, Atsunobu Masuno

    Materials Research Bulletin   109   190 - 194   2019年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    © 2018 Elsevier Ltd An oxide system Sc2−xFexO3 prepared by a conventional solid-state reaction method was found to change its color from the well-known reddish color at x = 2.0 to a yellowish color at x ≈ 0.6 and to a greenish-yellow color at 0.2 ≤ x ≤ 0.4. According to the structural characterization results for this system, the monophasic corundum phase region persists for 1.6 ≤ x ≤ 2.0, whereas the bixbyite-type phase is monophasic for 0 ≤ x ≤ 1.0. The intermediate region of 1.2 ≤ x ≤ 1.4 is a mixed region. Because green is a rare color for iron oxides, powder of the most typical composition, x = 0.4, with (L*, a*, b*) coordinates of (77.3, −0.5, 51.0) was tested as a pigment for a Japanese-style painting and also as an overglaze enamel on porcelain; reasonably good results were obtained.

    DOI: 10.1016/j.materresbull.2018.09.035

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  • Influence of cobalt source compounds on the color tone of cobalt blue inorganic pigment

    Mika Yoneda, Yuya Tatsumi, Yasushi Mino, Koichi Nakaso, Kuniaki Gotoh, Makoto Nakanishi, Tatsuo Fujii, Yasuhiro Konishi, Toshiyuki Nomura

    Journal of the Society of Powder Technology, Japan   56 ( 8 )   446 - 451   2019年

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    掲載種別:研究論文(学術雑誌)  

    The color tone of pigments is affected by various factors such as crystal structure and particle size. These characteristics should be determined by synthesis condition. In this study, the influence of cobalt source on the color tone of cobalt blue pigment was investigated. Cobalt blue (CoAl2O4) was synthesized by solid-state reaction method. Co3O4 and Co(OH)2 with two different particle sizes were used as the cobalt source, and γ-Al2O3 was used as the aluminum source. The products were characterized by spectrophotometry, XRD, SEM, and TG/DTA. It was revealed that the chroma of the synthesized cobalt blue depends on the cobalt source. The cobalt blue synthesized using smaller size Co(OH)2 showed most vivid color. It was suggested that the number of the contact points between the starting materials increased with decreasing the particle size, leading to the progress of the reaction.

    DOI: 10.4164/sptj.56.446

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  • Cathepsin K inhibitor causes changes in crystallinity and crystal structure of newly-formed mandibular bone in rats 査読 国際誌

    Y. Yoshioka, E. Yamachika, M. Nakanishi, T. Ninomiya, K. Nakatsuji, Y. Kobayashi, T. Fujii, S. Iida

    British Journal of Oral and Maxillofacial Surgery   56 ( 8 )   732 - 738   2018年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    Cathepsin K inhibitors are new drugs with the potential for the treatment of osteoporosis because they sustain bony remodelling better than bone resorption inhibitors such as bisphosphonates. The treatment of osteoporosis with inhibitors of bony resorption is associated with osteonecrosis of the jaw, as the deterioration in bony quality that they induce is thought to be one of its causes. The quality of bone is delineated by structural and material characteristics (which include the degree and quality of mineralisation, and depends on the content of proteoglycan and the structural integrity of the bony collagen).1,2 Animal and clinical studies have shown that cathepsin K inhibitors improve the mineral density and structural characteristics of bone, but their effect on the rest remains unknown. We therefore hypothesised that these inhibitors will affect the material characteristics of newly-formed mandibular bone. To verify our hypothesis, we used Raman microspectroscopy to examine such bone in rats that were given a cathepsin K inhibitor, and found unusual crystallinity and an increased substitution of carbonate (CO32-) in its crystal structure.

    DOI: 10.1016/j.bjoms.2018.08.003

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  • スパッタ法によるエピタキシャルFe3-xTixO4固溶体薄膜の作製 査読

    西村和泰, 北園昌弘, 中西真, 藤井達生

    粉体および粉末冶金   65 ( 9 )   585 - 588   2018年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.2497/jjspm.65.585

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  • Molecular alterations of newly formed mandibular bone caused by zoledronate 国際誌

    Y. Yoshioka, E. Yamachika, M. Nakanishi, T. Ninomiya, K. Nakatsuji, M. Matsubara, N. Moritani, Y. Kobayashi, T. Fujii, S. Iida

    International Journal of Oral and Maxillofacial Surgery   47 ( 9 )   1206 - 1213   2018年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    Bone quality is defined by structural and material characteristics. Most studies on the mandible have focused on the analysis of structural characteristics, with insufficient investigation of material characteristics. This study tested whether zoledronate affects the material characteristics of newly formed mandibular bone. Thirty-six female Wistar rats were assigned to three groups: sham-ovariectomized rats (SHAM, n=12), ovariectomized rats (OVX, n=12), and ovariectomized rats treated with zoledronate (ZOL, n=12). The left side of the mandibular ramus of all rats was drilled bicortically. Twenty-eight days after surgery, all surviving rats were euthanized and all mandibles were removed. Raman microspectroscopy was performed, and five spectra per specimen of newly formed mandibular bone were analysed. Compared with OVX rats, the mineral/matrix ratio in ZOL rats was significantly increased (5.43±1.88 vs. 7.86±2.05), while crystallinity (0.055±0.002 vs. 0.050±0.002), relative proteoglycan content (0.43±0.10 vs. 0.31±0.05), and collagen structural integrity (1.16±0.21 vs. 0.72±0.06) were significantly decreased. These changes in material characteristics may explain why rats that received zoledronate exhibited peculiar biological phenomena such as bisphosphonate-related osteonecrosis of the jaw.

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  • Cuticle network and orientation preference of photonic crystals in the scales of the weevil Lamprocyphus augustus

    R. Ebihara, H. Hashimoto, J. Kano, T. Fujii, S. Yoshioka

    Journal of The Royal Society Interface   15 ( 145 )   20180360 - 20180360   2018年8月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:The Royal Society  

    This paper reports the structural and optical investigations of the structural colour of the weevil
    <italic>Lamprocyphus</italic>
    <italic>augustus</italic>
    . The photonic crystal structure within the weevil's scales was investigated using sequential focused ion-beam milling and scanning electron microscopy imaging. We carefully analysed the reconstructed three-dimensional structure to determine the unit cell of the photonic crystal. It was found that the cuticle network of the cubic unit cell perfectly matches the previously reported diamond-based network. However, different results were obtained for the crystal orientations of the small crystal domains that comprise the entire photonic crystal structure in the scales:
    <monospace>&lt;111&gt;</monospace>
    directions are highly preferred along the surface normal of the scale. This finding explains the fact that the scale is almost uniformly coloured despite the multi-domain structure. It is confirmed experimentally and theoretically that the wavelength range of the reflection band corresponds to the gap of the photonic band.

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    その他リンク: https://royalsocietypublishing.org/doi/full-xml/10.1098/rsif.2018.0360

  • 電場印加前後でのBaTiO3内殻原子軌道のエネルギー準位計測

    押目 典宏, 伊藤 満, 藤井 達生, 保井 晃, 狩野 旬, 池永 英司, 安井 伸太郎, 日隈 聡士, 池田 直, 濱嵜 容丞, 安原 颯, 横谷 尚睦

    日本物理学会講演概要集   73   2571 - 2571   2018年

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    記述言語:日本語   出版者・発行元:一般社団法人 日本物理学会  

    DOI: 10.11316/jpsgaiyo.73.1.0_2571

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  • 分極効果で変調される強誘電体BaTiO3の電子構造

    押目 典宏, 伊藤 満, 藤井 達生, 保井 晃, 狩野 旬, 池永 英司, 安井 伸太郎, 日隈 聡士, 池田 直, 濱嵜 容丞, 安原 颯, 横谷 尚睦

    日本物理学会講演概要集   72   2307 - 2307   2017年

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    記述言語:日本語   出版者・発行元:一般社団法人 日本物理学会  

    DOI: 10.11316/jpsgaiyo.72.2.0_2307

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  • 21aAF-3 BaTiO_3のバンド構造におけるイオン欠損効果

    押目 典宏, 狩野 旬, 池田 直, 寺西 貴志, 大崎 浩司, 藤井 達生, 上田 剛慈, 大久保 智子

    日本物理学会講演概要集   71   2691 - 2691   2016年

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

    DOI: 10.11316/jpsgaiyo.71.1.0_2691

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  • 21aPS-115 金属-強誘電体接合系における触媒作用

    重名 智博, 狩野 旬, 池田 直, 藤井 達生, 大久保 智子

    日本物理学会講演概要集   71   2708 - 2708   2016年

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

    DOI: 10.11316/jpsgaiyo.71.1.0_2708

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  • Mnをドープした単結晶Yb2Fe3O7の誘電特性

    烏谷 友之, 藤原 孝将, 藤井 達生, 戸取 和大, 福永 守, 堀部 陽一, 狩野 旬, 池田 直

    日本物理学会講演概要集   71   2543 - 2543   2016年

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    記述言語:日本語   出版者・発行元:一般社団法人 日本物理学会  

    <p>Yb_2_Fe_3_O_7_は層状希土類複電荷酸化鉄YbFe_2_O_4_の同族物質であり,どちらもWレイヤーと呼ばれるFe-Oの二重層を持つ。Wレイヤー内では電子が規則配列をし,電子の偏りが起こり,電子の濃淡による新しい機構の強誘電性が発現すると期待されている。最近MnをドープしたYb_2_Fe_3_O_7_のセラミックのP-Eヒステリシスループが報告された。だがセラミック試料では粒界にトラップされた電荷の効果も起こり得る。今回我々は単結晶を作成し、誘電性の異方性を調べ報告する。</p>

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  • α-Fe2O3, Fe3O4, FeO粉末のバンド構造

    押目 典宏, 狩野 旬, 岡本 拓巳, 池田 直, 藤井 達生

    日本物理学会講演概要集   71   2545 - 2545   2016年

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    記述言語:日本語   出版者・発行元:一般社団法人 日本物理学会  

    <p>前回の日本物理学会2016年次大会では,強誘電体バンド構造のイオン欠損効果を光反射率スペクトルと光電子収量分光スペクトルから議論した。今回はFeイオン価数の異なるFe酸化物を3種類用意し,前回と同様の測定を行ったところ,FeとOの比率に対しバンド構造のエネルギー深さが系統的に変化することがわかったので,今回報告する。</p>

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  • High-Rate Capabilities of Ferroelectric BaTiO3-LiCoO2 Composites with Optimized BaTiO3 Loading for Li-Ion Batteries 査読

    Takashi Teranishi, Yumi Yoshikawa, Ryo Sakuma, Hirokazu Okamura, Hideki Hashimoto, Hidetaka Hayashi, Tatsuo Fujii, Akira Kishimoto, Yasuo Takeda

    ECS ELECTROCHEMISTRY LETTERS   4 ( 12 )   A137 - A140   2015年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELECTROCHEMICAL SOC INC  

    Ferroelectric barium titanate, BaTiO3 (BT) was coated on lithium cobaltate, LiCoO2 (LC), as an artificial solid electrolyte interface (SEI), via the simple sol-gel route. The high charge-discharge rate capabilities of the composite cathodes were evaluated up to 10C. The LC loaded with 1 mol% of BT had a measured capacity of 146 mAh/g, which was the highest value measured at 10C. This capacity was 78% of its initial value, and was 238% of the capacity of bare LC over the same number of cycles. (C) 2015 The Electrochemical Society. All rights reserved.

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  • 21pCJ-7 Ba_<0.8>Sr_<0.2>TiO_3のMgドープ効果

    押目 典宏, 狩野 旬, 大崎 浩司, 寺西 貴志, 吉田 右, 池田 直, 藤井 達生, 大久保 智子, 上田 剛慈

    日本物理学会講演概要集   70   2704 - 2704   2015年

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

    DOI: 10.11316/jpsgaiyo.70.1.0_2704

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  • 22pCH-13 金属-強誘電体接合系での触媒作用

    狩野 旬, 池田 直, 押目 典宏, 藤井 達生, 橋本 英樹, 寺西 貴志, 大久保 智子, 上田 剛慈, 吉田 右, 秋山 雄介

    日本物理学会講演概要集   70   2743 - 2743   2015年

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

    DOI: 10.11316/jpsgaiyo.70.1.0_2743

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  • High-rate performance of ferroelectric BaTiO3-coated LiCoO2 for Li-ion batteries 査読

    Takashi Teranishi, Yumi Yoshikawa, Ryo Sakuma, Hideki Hashimoto, Hidetaka Hayashi, Akira Kishimoto, Tatsuo Fujii

    APPLIED PHYSICS LETTERS   105 ( 14 )   2014年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    The high charge-discharge rate characteristics of composite cathodes consisting of ferroelectric BaTiO3 (BT)-coated LiCoO2 (LC), synthesized via a simple sol-gel route, were evaluated, and the rate showed stepwise increases to as high as 5C. The LC-BT composite cathode annealed at 600 degrees C, LC-BT-600, notably retained high capacities, i.e., 122 mAh/g at 30 cycles, 5C and 99 mAh/g at 60 cycles, 5C. These capacities corresponded to 83% and 67% of the initial values and were as high as 158% and 245% of the capacities of bare LC over the same cycles, respectively. The ferroelectricity of the coated BT contributed to the improvement in high-rate performance. (c) 2014 AIP Publishing LLC.

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  • Mössbauer spectrum of high-pressure synthesized ilmenite-type FeGeO<inf>3</inf> 査読

    T. Fujii, D. Nakatsuka, M. Nakanishi, J. Takada, T. Yoshino

    Hyperfine Interactions   226 ( 1-3 )   275 - 280   2014年4月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    Ilmenite-type FeGeO3was prepared by high-pressure synthesis technique using a Kawai-type multi-anvil apparatus at 23.5 GPa and 500 °C. The effects of post annealing on the high-pressure synthesized samples were investigated by XRD analysis, Mössbauer spectroscopy and SQUID-magnetization measurements. The subsequent annealing after the high-pressure synthesis was effective to improve the crystallinity and increased the crystallite size of the ilmenite-type FeGeO3. The room temperature Mössbauer spectrum was composed of sharp paramagnetic doublets assigned to Fe2+. The well-crystallized ilmenite-type FeGeO3showed typical antiferromagnetic behavior with the Néel temperature of 79 K, while the as-prepared sample without annealing demonstrated the superparamagnetic characteristics with larger magnetization. © 2014 Springer International Publishing Switzerland.

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    その他リンク: http://orcid.org/0000-0002-5422-7396

  • 熊本県下扇原遺跡出土古代ベンガラのキャラクタリゼーション 査読

    辻 広美, 村上 隆, 宮崎敬士, 橋本英樹, 團野瑛章, 草野圭弘, 菊地孝宏, 中西 真, 藤井 達生, 高田 潤

    粉体および粉末冶金   60 ( 4 )   146 - 153   2013年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japan Society of Powder and Powder Metallurgy  

    To clarify the detailed features of the red bengala samples excavated from the Shimo-ohgibaru archaeological site in the late Yayoi period (2nd to 3rd century A.D.) from the viewpoint of materials science, colorimetric measurements, X-ray fluorescence analyses, X-ray diffraction measurements, transmission electron microscope observations, and surface area measurements of the ancient bengala samples were achieved. The ancient bengala sample was found to be high purity α - Fe2O3. The features of the color tone and particle size of the ancient bengala were clarified by comparing with those of commercially available bengala, Fukiya bengala, and synthesized α-Fe2O3. In addition, the starting materials and synthesis processes of the ancient bengala were discussed by applying the elutriation experiments of representative natural hematite and heat-treated natural iron hydroxide (Oniita).

    DOI: 10.2497/jjspm.60.146

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  • 微生物が作るマンガン酸化物の加熱処理による結晶構造と微細構造の変化 査読

    木村倫康, 橋本英樹, 宮田直幸, 仁科勇太, 草野圭弘, 池田靖訓, 中西真, 藤井達生, IVO Safarik, IVO Safarik, MIRKA Safarikova, 高田潤

    粉体および粉末冶金   60 ( 3 )   92-99 (J-STAGE) - 99   2013年

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    記述言語:日本語   出版者・発行元:Japan Society of Powder and Powder Metallurgy  

    In the natural aquatic environment, there are various types of biogenic manganese oxide (BMO) precipitates which are produced by manganese oxidizing microorganisms, at ambient temperature, atmosphere and neutral pH.BMO is a very interesting and useful functional material because of its unique property; hollow globule shape formed by nanosheets, large surface area and photocatalytic characteristics. In this study, thermally-processed BMO at 100 − 1000 °C was analyzed by XRD, XANES, SEM, TEM and nitrogen adsorption method to reveal the effects of heat-treatment on its crystal structure, Mn valence state, globule morphology, microstructure, pore size distribution and specific surface area. In the result, morphology of BMO is maintained below 800 °C, while nanosheets composing BMO were changed into nanoparticles at 600 °C. The crystal structure was transformed from birnessite into hausmannite (Mn3O4) at 600 °C. The specific surface area was increased by heat-treatment between 300 and 500 °C. In cases of artificial manganese oxides, such changes of crystal structure and specific surface area were not observed, and combustion of organic materials produced by microorganisms in BMO probably has a large effect on them.

    DOI: 10.2497/jjspm.60.92

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  • Synthesis of the Sr3Zn2Fe24O41 Z-type ferriteby polymerizable complex method

    Takuya Tainaka, Takeyuki Kikuchi, Tatsuya Nakamura, Tohru Yamasaki, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Yasunori Ikeda

    ELECTROCERAMICS IN JAPAN XV   566   231 - 234   2013年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:TRANS TECH PUBLICATIONS LTD  

    Synthesis of Sr3Zn2Fe24O41 Z-type ferrite was investigated. Precursors of ferrite were prepared by polymerizable complex method. Identification of formed phases in the obtained samples and determination of lattice parameters of Z-type ferrite were performed by powder X-ray diffraction (XRD). Single-phase of Sr3Zn2Fe24O41 Z-type ferrite was synthesized by heating at 1463 K for 5hours in air. M-H curve of prepared single-phase Sr3Zn2Fe24O41 Z-type ferrite was measured by using vibrating sample magnetometer (VSM). It was revealed that Sr3Zn2Fe24O41 Z-type ferrite has larger saturation magnetization (23.5 mu(B)/formula unit) than that of Sr3Co2Fe24O41 (22.7 mu B/formula unit) and shows characteristic two-step saturation of magnetization as well as Sr3Co2Fe24O41 Z-type ferrite.

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  • Synthesis of U-type strontium hexaferrite by polymerizable complex method

    Takeyuki Kikuchi, Shinji Yoshida, Tatsuya Nakamura, Tohru Yamasaki, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Yasunori Ikeda

    ELECTROCERAMICS IN JAPAN XV   566   227 - 230   2013年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:TRANS TECH PUBLICATIONS LTD  

    Synthesis of U-type hexaferrite was investigated in the various strontium-based systems (Sr-Me-Fe-O system, Me = Co, Zn, Cu, and Ni). Precursors of ferrites were prepared by polymerizable complex method. Sr4Me2Fe36O60 (Me = Co and Zn) U-type hexaferrites were synthesized at the temperature range between 1423 and 1483 K in air. Coercivity of obtained ferrite was decreased with increasing heat treatment temperatures. Cu substitution reduced formation temperature of U-type hexaferrite.

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  • Preparation, microstructure, and color tone of microtubule material composed of hematite/amorphous-silicate nanocomposite from iron oxide of bacterial origin 査読

    Hideki Hashimoto, Hiroshi Asaoka, Takuya Nakano, Yoshihiro Kusano, Hiromichi Ishihara, Yasunori Ikeda, Makoto Nakanishi, Tatsuo Fujii, Tadanori Yokoyama, Nanao Horiishi, Tokuro Nanba, Jun Takada

    DYES AND PIGMENTS   95 ( 3 )   639 - 643   2012年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    By heating an amorphous iron oxide produced by Leptothrix ochracea, an iron-oxidizing bacterium species, at 600-1100 degrees C in air for 2 h, vivid red-colored powdered materials including alpha-Fe2O3 (hematite) and amorphous silicate with high thermostability were prepared which offer potential for use as over-glaze enamels on porcelain. The precise color tone of the materials greatly depends on the heat-treatment temperature. The most strikingly beautiful sample, heat-treated at 800 degrees C, is light yellowish-red in color (L* = 47.3, a* = 34.1, and b* = 34.6), has a unique microstructure, and does not fade in color even with reheating at 800 degrees C, which is the firing temperature for over-glaze enamel on porcelain. The sample primarily consists of crystalline hematite particles similar to 40 nm in diameter with slightly longer axis unit-cell parameters than those of pure hematite. The particles are covered with amorphous silicate phase similar to 5 nm in thickness and are intricately interconnected into microtubules with an average diameter of 1.26 mu m. The attractive color of this material is due to the following structural features: small particle size (similar to 40 nm). nanocomposite of hematite and amorphous silicate, and a microtubule structure that inhibits aggregation of individual hematite particles and microtubules. (C) 2012 Elsevier Ltd. All rights reserved.

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  • ビックスバイト型β-Fe2O3の生成機構 査読

    團野瑛章, 草野圭弘, 浅岡裕史, 中西真, 藤井達生, 池田靖訓, 高田潤

    粉体および粉末冶金   58 ( 9 )   529 - 534   2012年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japan Society of Powder and Powder Metallurgy  

    Formation mechanism of β-Fe2O3 particles was investigated by controlling the preparation conditions such as the mixing ratio of NaFe(SO4)2 and Na3Fe(SO4)3 to NaCl and the heat treatment temperature. The heat treatment temperature strongly affected the particle shapes and sizes. β-Fe2O3 was found to be formed by two different reactions; one is a solid state reaction below 490 °C, and another is a liquid phase-mediated reaction above 490 °C. β-Fe2O3 had granular shape with a diameter of about 50 to 100 nm below 490 °C, while at high temperatures above 490 °C cubic particles with relatively large size of about 500 nm to 2 μm were produced. We found that this dramatically change of particle morphology including their sizes and shapes was caused by the effects of the liquid phase in the reaction.

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  • Formation and superparamagnetic behaviors of LaFeO3 nanoparticles 査読

    Tatsuo Fujii, Ikkoh Matsusue, Makoto Nakanishi, Jun Takada

    HYPERFINE INTERACTIONS   205 ( 1-3 )   97 - 100   2012年3月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPRINGER  

    Formation of LaFeO3 nanoparticles obtained from thermal decomposition of organometallic precursors was investigated as a function of the heat-treatment temperature. The precursors heat-treated below 300 degrees C were amorphous, but above 350 degrees C a single-phase of nanocrystalline LaFeO3 was formed. The LaFeO3 nanoparticles showed the superparamagnetic behavior in both magnetization and Mossbauer measurements. With increasing heat-treatment temperature, the crystallite size of LaFeO3 nanoparticles was gradually increased. The quadrupole splitting and isomer shift of paramagnetic doublet pattern were affected by the growth of LaFeO3 particles.

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  • Synthesis of La-Co Substituted M-type Calcium Hexaferrite by Polymerizable Complex Method 査読

    T. Kikuchi, T. Nakamura, T. Yamasaki, M. Nakanishi, T. Fujii, J. Takada, Y. Ikeda

    3RD INTERNATIONAL CONGRESS ON CERAMICS (ICC3): ADVANCES IN ELECTRO CERAMICS   18   2011年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IOP PUBLISHING LTD  

    Synthesis of La-Co substituted M-type Calcium hexaferrite was studied. Samples were prepared by polymerizable complex method. High purity reagent of strontium carbonate, iron (III) nitrate ennnahydrate, cobalt (II) nitrate hexahydrate and lanthanum oxide were used as starting materials. Prepared aqueous solution was heated for dehydration and gelling. Thermal pyrolysis was carried out by heating the gel. The obtained precursor powders were ground with an alumina mortar and compacted by uniaxial pressing into disk specimens and then heated at temperature range between 1173 K and 1573 K in air. Phase identification and determination of lattice parameters were carried out by powder X-ray diffraction (XRD). Scanning Electron Microscope (SEM) was utilized to investigate the microstructure of the polycrystalline ferrites. Magnetic properties were discussed by magnetization measurements by measuring of M-H curve with vibrating sample magnetometer (VSM). Single-phase of M-type hexaferrite was obtained at lower temperature relative to by conventional synthesis.

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  • Formation mechanism of nano-crystalline β-Fe<inf>2</inf>O<inf>3</inf> particles with bixbyite structure and their magnetic properties 査読

    T. Danno, H. Asaoka, M. Nakanishi, T. Fujii, Y. Ikeda, Y. Kusano, J. Takada

    Journal of Physics: Conference Series   200 ( SECTION 8 )   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IOP PUBLISHING LTD  

    Formation mechanism of nano-crystalline β-Fe O particles was investigated by controlling the preparation conditions such as the mixing ratio of NaFe(SO ) to NaCl and heating treatment temperature. A single phase of β-Fe O was formed regardless of the mixing ratio. The heat treatment temperature strongly affected the particle shapes and sizes. Below 490 °C, they had granular shape with a diameter of about 50 to 100 nm. While, above 490 °C, cubic particles with increased size of about 1 μm were produced. All samples were antiferromagnetic at low temperature. The Néel temperature (T ) of 119 K for the large cubic particles was decreased to 113 K for the nanoparticles. © 2010 IOP Publishing Ltd. 2 3 4 2 2 3 N

    DOI: 10.1088/1742-6596/200/8/082003

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  • Synthesis of Ge substituted ilmenite and their magnetic and electronic properties 査読

    D. Nakatsuka, T. Fujii, M. Nakanishi, J. Takada

    Journal of Physics: Conference Series   200 ( SECTION 1 )   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IOP PUBLISHING LTD  

    Ilmenite (FeTiO ) is an antiferromagnetic insulator with Néel temperature (T ) of 55 K. The magnetic structure of FeTiO is known to be easily frustrated by cation substitution. In the present study we tried to prepare the Ge-substituted FeTiO . The samples were prepared by the conventional solid state reaction technique under the controlled oxygen pressure. Formation of a single phase of FeTi Ge O with x=0.01 was confirmed by X-ray diffraction (XRD) method. The Ge-substituted FeTiO had a smaller lattice volume than that of un-doped one. SQUID magnetometer and Mössbauer spectroscopy measurements indicated that the Ge-substitution reduced the T slightly. Moreover the magnetic hyperfine fields of Ge-substituted FeTiO seemed to be increased in spite of the decreased magnetic moments. © 2010 IOP Publishing Ltd. 3 N 3 3 1-x x 3 3 N 3

    DOI: 10.1088/1742-6596/200/1/012144

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  • Microstructure and formation process of reddish color pattern hidasuki on bizen stoneware

    Yoshihiro Kusano, Minoru Fukuhara, Tatsuo Fujii, Jun Takada, Akira Doi, Yasunori Ikeda, Mikio Takano

    ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES   64   C165 - C165   2008年

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    記述言語:英語   出版者・発行元:INT UNION CRYSTALLOGRAPHY  

    DOI: 10.1107/S0108767308094683

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  • 27pTE-9 Fe_<2-x>Ti_xO_3固溶体中のTi^<4+>イオンの磁気分極(27pTE 磁気共鳴一般・実験技術開発・酸化物磁性,領域3(磁性,磁気共鳴)) 査読

    藤井 達生, 山下 美樹, 藤森 伸一, 齋藤 祐児, 中村 哲也, 小林 啓介, 高田 潤

    日本物理学会講演概要集   61 ( 0 )   435 - 435   2006年

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    記述言語:日本語   出版者・発行元:一般社団法人 日本物理学会  

    DOI: 10.11316/jpsgaiyo.61.1.3.0_435_1

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  • Magnetic properties of La-Co substituted M-type Sr ferrite ultra fine powders prepared from the citrate precursors 査読

    T Kikuchi, T Nakamura, M Nakanishi, T Fujii, J Takada, Y Ikeda, M Nakamura, M Miki

    NINTH INTERNATIONAL CONFERENCE ON FERRITES (ICF-9)   75 - 80   2005年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:AMER CERAMIC SOC  

    Magnetic properties of La-Co substituted M-type Sr ferrite powders were studied. Samples were prepared from the citrate precursors. High purity reagent of Sr(NO3)(2), Fe(NO3)(3)(.)9H(2)O, Co(NO3)(2)(6H2O)-H-. and La2O3 were used as starting materials. They were dissolved in distilled water with citric acid. The nominal molar ratio of the mixed solutions were I : 5 of metal : citric acid. Prepared aqueous solution was heated at 120 degrees C for dehydration and gelling. Thermal pyrolysis was carried out by heating the gel at the temperature range between 300 degrees C and 350 degrees C for 1h in air. The obtained precursor powders were ground with an alumina mortar and compacted by uniaxial pressing into disk specimens, 20 mm in diameter and I mm thick, and then heated at temperature range between 750 degrees C and 900 degrees C in air. Phase identification and determination of lattice parameters were carried out by powder X-ray diffraction (XRD). Scanning Electron Microscope (SEM) was utilized to investigate the microstructure of the polycrystalline ferrites. Magnetic properties were discussed by magnetization measurements by using a vibration sample magnetometer (VSM) at a maximum applied field of 16 kOe. Magnetization and coercive force were measured at room temperature. Temperature dependence of residual magnetization was measured for determine the Curie temperature. The La-Co substituted SrM ferrite powders prepared in this study showed typical magnetic hysterisis of hard ferrite. Extreme enhancement of coercive force was performed by La-Co substitution. Maximum value of coercive force achieved in this study is 8.0 kOe. This enhancement of coercive force is realized by mainly increase of magnetocrystal line anisotropy caused by La-Co substitution.

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  • Magnetic and electronic properties of Fe<inf>1.2</inf>Ti <inf>0.8</inf>O<inf>3</inf>/Fe<inf>2</inf>O<inf>3</inf> bilayered films

    Tatsuo Fujii, Yusuke Takada, Makoto Nakanishi, Jun Takada

    INTERMAG ASIA 2005: Digests of the IEEE International Magnetics Conference   728   2005年

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    掲載種別:研究論文(国際会議プロシーディングス)  

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  • Preparation and magnetic property of Y-type hexagonal ferrite's films 査読

    K Komatsu, M Nakanishi, T Fujii, J Takkada

    NINTH INTERNATIONAL CONFERENCE ON FERRITES (ICF-9)   759 - 762   2005年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:AMER CERAMIC SOC  

    Well-crystallized Y-type hexagonal ferrite films with highly c-axis orientation were successfully preparated on Ag substrates by polymerized complex method. The Co-2-Y phase started to form at 780 degrees C and nearly single-phase Of Co-2-Y was formed when the films heat-treated above 820 degrees C. The films had large in-plane magnetic anisotropy with small in-plane Hc of about 300 Oe. When it was heat-treated at 860 degrees C, the Ms had maximam value of 192 emu/cm(3). The heat-treatment time also influence the magnetic properties of the films. The films with nearly the single-phase Of Co-2-Y were formed when the films had stoichiometric Ba:Co:Fe ratio of 1:1:6.

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  • Preparation and characterization of alpha-Fe2O3/FeTiO3 multi-layered films 査読

    T Fujii, Y Takada, M Nakanishi, J Takada

    NINTH INTERNATIONAL CONFERENCE ON FERRITES (ICF-9)   207 - 213   2005年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:AMER CERAMIC SOC  

    Thin films of the hematite-ilmenite solid solution (ot-Fe2O3-FeTiO3) are one of the candidates for practical magnetic semiconductors with a high Curie temperature (Tc). We have successfully prepared well-crystallized epitaxial Fe1.2Ti0.8O3 films on alpha-Al2O3 substrates by using a reactive helicon plasma sputtering technique. Only the films having the R3 symmetry had large ferrimagnetic moments, where the Fe-rich and the Ti-rich cation layers were alternately stacked along the c-axis. To obtain the order structure (R3) for the Fe1.2Ti0.8O3 films, a higher substrate temperature and/or post annealing at 600 degrees C were very effective. Unfortunately the Fe1.2Ti0.8O3 solution has the lower Tc of about 250 K in bulk form. Trying to raise up the Tc of Fe1.2Ti0.8O3 multilayered films of alpha-Fe2O3/Fe1.2Ti0.8O3 were also prepared. At the moment, though, we did not success the preparation of high-Tc multilayered films beyond the room temperature. Low temperature magnetization measurements and Mossbauer spectroscopy suggested that the exchange coupling between alpha-Fe2O3 and Fe1.2Ti0.8O3 seemed to provide a large possibility to increase the Tc of Fe1.2Ti0.8O3 layers beyond the room temperature.

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  • Preparation and characterization of al-substituted hematite and their tone color 査読

    H Asaoka, M Nakanishi, T Fujii, J Takada, R Murakami

    NINTH INTERNATIONAL CONFERENCE ON FERRITES (ICF-9)   69 - 73   2005年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:AMER CERAMIC SOC  

    Hematite (alpha-Fe2O3) is one of the most primitive and attractive red pigments. The particle size of hematite seriously influences the reddish tone. The particle with the smallest size of about 100 nm had yellowish red color. With increasing the particle size, the tone color changed systematically from yellowish red to red, dark red, and dark purple. To control the tone color of hematite we prepared Al-substituted Hematite (alpha-(Fe1-xAlx)(2)O-3) by polymerized complex method using iron nitrate (Fe(NO3)(3)-9H(2)O) and aluminum nitrate (Al(NO3)(3)-9H(2)O) as starting materials. The precursors were heat-treated at the temperature between 500 degrees C and 1100 degrees C for 2 hours. When the samples were heat-treated at 1100 degrees C, the solubility limit of Al in hematite up to 13%. The particle size of the sample heat-treated at 1000 degrees C without Al substitution was about 2 pm, while the one with 10% Al-substitution was about 200 nm. The Al substitution suppressed the grain growth of hematite. With increasing the Al content, the temperature at which the color of hematite changed from yellowish red to dark purple increased monotonically. Moreover the Al-substitution seemed to stabilize the maghemite phase (gamma-Fe2O3) at higher temperature.. The XRD pattern of Al-substituted samples heat-treated at 700 degrees C showed some diffraction lines assigned to gamma-Fe2O3. This would be a reason to suppress the grain growth of hematite.

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  • Low temperature synthesis of Sr and Ba M-type ferrites by polymerized complex method 査読

    T. Kikuchi, T. Nakamura, M. Nakanishi, T. Fujii, J. Takada, Y. Ikeda, M. Nakamura, M. Miki

    Trans Mater Res Soc Jpn   29   2305 - 2308   2004年

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    Synthesis and magnetic properties of M-type hexagonal ferrites with chemical composition of AFe12O19 (A = Ba and Sr) were studied. Nitrates of barium, strontium and iron were used as starting materials. The precursor of M-type ferrites was prepared mainly by the polymerization of metal-citric complex with various amounts of ethylene glycol, and heating the gel at 300 oC. The precursor was ground, pressed by uniaxial compression in a die and heated at 750-950 oC in air. From these results, large coercive force of the samples in this study is probably caused by achievement of small grain size under the single domain size by polymerized complex method.

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  • Reproduction of Japanese traditional pigment based on iron oxide powders with yellowish red color 査読

    Hiroshi Asaoka, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Yoshihiro Kusano, Ryu Murakami

    Materials Research Society Symposium - Proceedings   712   435 - 440   2002年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:MATERIALS RESEARCH SOCIETY  

    Since the beginning of the 18th century A.D., an artificial iron oxide pigment (hematite, called "bengara" in Japanese) and having a beautiful yellowish red color, has been produced in Japan and applied to pottery, textiles and paintings. However, in 1965 the traditional "bengara" could not be produced anymore, mainly because of environmental pollution. The purpose of this study is to make clear the features of traditional "bengara" and to reproduce high quality "bengara" using modern high-purity reagents. Traditional "bengara" has been characterized as hematite containing a small amount of Al. The average size of the "bengara" particles is approximately 100 nm. The color becomes more yellowish-red with increasing Al content. A monophase of hematite prepared by heating a mixture FeSO -7H O and α-Al O to about 680°C included a small amount of Al substituted in a solid solution. The particle size greatly decreased as the heat treatment temperature was decreased : 100 nm at 770°C but 50 nm at 650°C. The color of the particles becomes more vivid as the temperature is decreased, but within bounds this color is independent of the amount of Al in solid solution. 4 2 2 3

    DOI: 10.1557/proc-712-ii8.2

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  • NO<inf>2</inf>-assisted molecular-beam epitaxy of wustitelike and magnetitelike Fe oxynitride films on MgO(100)

    F. C. Voogt, P. J. Smulders, G. H. Wijnja, L. Niesen, T. Fujii, M. A. James, T. Hibma

    Physical Review B - Condensed Matter and Materials Physics   63 ( 12 )   1254091 - 12540911   2001年

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    掲載種別:研究論文(学術雑誌)  

    In an attempt to obtain wustite Fe O as epitaxial films on MgO(100), NO -assisted molecular-beam epitaxy was applied. At low NO fluxes, the low-energy electron diffraction and reflection high-energy electron diffraction images indeed indicate the formation of a rocksaltlike structure. In addition, Mössbauer spectroscopy provides evidence for the formation of a phase that is paramagnetic at room temperature. However, the layers are not pure oxides but are well-ordered oxynitrides with composition Fe O N . The nitrogen atoms occupy substitutional sites on the oxygen-anion sublattice. Similarly, at slightly higher NO fluxes, magnetitelike oxynitride films with composition Fe O N are obtained. By correlating x-ray photoelectron spectroscopy spectra with the intensity oscillation periods observed during reflection high-energy electron diffraction, it is possible to derive the complete stoichiometry of the films. We propose that the abrupt incorporation of nitrogen atoms only occurs if the atomic oxygen provided by the NO flux is insufficient to form a stoichiometric Fe O . 1-x 2 2 1-x 1-y y 2 3+δ 4-y y 2 3 4

    DOI: 10.1103/physrevb.63.125409

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  • 290MeV/n 40Ar照射によるBi‐2223焼結体へのピニングセンター導入の試み

    菊池丈幸, 中西真, 長江正寛, 草野圭弘, 藤井達生, 高田潤, 安田仲宏, 村上健

    粉体および粉末冶金   46 ( 9 )   994 - 998   1999年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人 粉体粉末冶金協会  

    Bi-2223 bulk superconductors were irradiated with 290MeV/n40Ar18+ions.40Ar18+irradiation effects on flux pinning of Bi-2223, which were estimated as ΔM from magnetic hysteresis loops measured by SQUID and VSM, were discussed. Irradiated samples had enlarged magnetic hysteresis loops than unirradiated samples. Moreover, the increment of ΔM depended on depth from the irradiation surface. Microstructure of irradiated samples were observed by high-resolution transmission electron microscopy (HR-TEM). However, irradiation defects such as the columnar defects were not observed in these samples.

    DOI: 10.2497/jjspm.46.994

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  • In situXPS analysis of various iron oxide films grown byNO2-assisted molecular-beam epitaxy

    T. Fujii, F. M. F. de Groot, G. A. Sawatzky, F. C. Voogt, T. Hibma, K. Okada

    Physical Review B   59 ( 4 )   3195 - 3202   1999年1月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:American Physical Society (APS)  

    DOI: 10.1103/physrevb.59.3195

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    その他リンク: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.59.3195/fulltext

  • Preparation and properties of a novel electromagnetic wave absorber ferrite/SiC sintered composite 査読

    T. Jun, M. Nakanishi, M.Yoshino, T. Fujii, Tatsuo, M. Fukuhara, A. Doi, Y. Kusano

    Adv. Powder Metall. Part. Mater.   3   11 - 19   1999年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • MBE-growth of iron and iron oxide thin films on MgO(100), using NO<inf>2</inf>, NO, and N<inf>2</inf>O as oxidizing agents

    F. C. Voogt, T. Hibma, P. J.M. Smulders, L. Niesen, T. Fujii

    Materials Research Society Symposium - Proceedings   477   211 - 216   1997年

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    掲載種別:研究論文(国際会議プロシーディングス)  

    We have made a study of the use of NO as the source of oxygen in the MBE-growth of iron oxides thin films. It is found that NO is a much more efficient oxidizing agent than molecular O . As indicated by Moessbauer spectroscopy, performed on Fe probe layers, NO is not only capable of forming stoichiometric magnetite Fe O , but also all non-stoichiometric Fe O phases. Even the metastable maghemite phase γ-Fe O (Fe O with δ = 1/3) can be formed. All iron oxides grow layer-by-layer-like, as indicated by strong RHEED intensity oscillations. When small doses of NO are used, new wustite Fe O and Fe O phases are formed. In contrast to the Fe O films, these phases have nitrogen incorporated into the crystal lattice. Similar compounds are obtained when NO is used as the source of oxygen. The use of N O does not lead to the formation of iron oxides. It does, however, alter the growth mode of Fe on MgO(100). Whereas Fe deposited under UHV conditions forms 3D islands, the N O acts as a surfactant and induces 2D layer-by-layer growth. 2 2 2 2 3 4 3-δ 4 2 3 3-δ 4 2 1-x 3 4 3-δ 4 2 2 57

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  • Raman Spectra and Constitution of Binary Tellurite Glasses Containing Typical Network Modifying Cations

    Akiyoshi Osaka, Qiu Jianrong, Tatsuo Fujii, Tokuro Nanba, Jun Takada, Yoshinari Miura

    Journal of the Society of Materials Science, Japan   42 ( 476 )   473 - 477   1993年

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    掲載種別:研究論文(学術雑誌)  

    The 720 and 780 cm components of the deconvoluted Raman spectra of glasses in the systems R O-TeO (R=Li, Na, K, Ba, Zn) were attributed to TeO groups and the 665 cm band was to TeO groups. The theoretical values of the molar ratio TeO /TeO derived from an assumed vitrification reaction were compared with the ratio derived from the intensity ratios of the Raman bands, I(720) /I(665) and I(780)/I(665). It was indicated that [O Te=O] and [O Te(=O)-O] units were induced by the addition of network modifying oxides in the composition range of lower atomic ratio O/Te. It was proposed that the decrease in the rate of increase of the ratio TeO /TeO in the range of larger O/Te was due to the equilibrium TeO ↔[O12/2Te=O] favoring the former unit. © 1993, The Society of Materials Science, Japan. All rights reserved. -1 -1 - n 2 3 4 3 4 2/2 1/2 3 4 4/2

    DOI: 10.2472/jsms.42.473

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  • Microstructure of Co Ferrite Films and Co Ferrite/zn Ferrite Double Layered Films Prepared by Plasma Enhanced MOCVD

    Eiji Fujii, Hideo Torii, Masumi Hattori, Tatsuo Fujii, Kiyoshi Kuribayashi, Miyoshi Inoue

    Journal of the Japan Society of Powder and Powder Metallurgy   40 ( 6 )   618 - 622   1993年

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    掲載種別:研究論文(学術雑誌)  

    Co Fe O (0. 1≤×≤1.0) films and a Co Fe O /Zn Fe O double layered film were prepared on soda-lime glass substrate (a=87×10 /deg) by plasma enhanced MOCVD and their microstructures and magnetic properties were studied. The Co ferrite films consisted of a random orientated initial layer (thickness < 100 nm) and an <100> orientated columnar layer. Conversion electron Mossbauer spectra and magnetization curves of the films indicated that the films had an easy axis perpendicular to the film plane. The Co ferrite film with higly perpendicular magnetic anisotropy could be obtained by using Zn ferrite film (thickness:210 nm) as a buffer layer between the Co ferrite film and the substrate. © 1993, Japan Society of Powder and Powder Metallurgy. All rights reserved. x a-x 4 0.1 2.9 4 0.5 2.5 4 -7

    DOI: 10.2497/jjspm.40.618

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  • Microstructure of Hydroxyapatite-Hematite Composite Particles Prepared by Ultrasonic Spray Pyrolysis

    Osaka Akiyoshi, Chiba Akira, Fujii Tatsuo, Nanba Tokuro, Takada Jun, Miura Yoshinari

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   39 ( 3 )   239 - 242   1992年

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    掲載種別:研究論文(学術雑誌)  

    Aqueous solutions of calcium nitrate stabilized with EDTA, ammonium dihydrogen orthophosphate and iron (III) nitrate were mixed before they were subject to ultrasonic spraying and to subsequent pyrolysis in an electric furnace, and particles of 0.45μm in average diameter consisting of hydroxyapatite and hematite were obtained. Surface morphology and microstructure of the particles were examined. A nucleus (hematite)-shell (hydroxyapatite) type structure was observed for larger particles (>0.8μm in diameter) though the particles of medium size apparently had a uniform microstructure. Such structural difference due to the particle size was explained in terms of decomposition of the Ca-EDTA chelating bond at lowest temperatures and temperature distribution in the sprayed mists. © 1992, Japan Society of Powder and Powder Metallurgy. All rights reserved.

    DOI: 10.2497/jjspm.39.239

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  • Cryogenic resonance-electron Mössbauer spectroscopy with a helium-filled proportional counter

    R. Katano, T. Fujii, T. Kobayashi, K. Fukumura, Y. Isozumi

    Nuclear Inst. and Methods in Physics Research, A   280 ( 2-3 )   285 - 287   1989年8月

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    掲載種別:研究論文(学術雑誌)  

    As studied in our previous works, a proportional counter filled with pure helium gas works well at low temperatures near 4.2 K. The helium-filled proportional counter (HFPC) provides us with a new method to detect nuclear radiations at low temperatures. A typical application of this counter is resonance-electron Mössbauer spectroscopy (REMS) at low temperatures (< ∼ 30 K). In this article some examples of REMS measurements with HFPC are given. © 1989.

    DOI: 10.1016/0168-9002(89)90918-2

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▼全件表示

書籍等出版物

  • エレクトロニクス用セラミックスの開発、評価手法と応用

    技術情報協会( 担当: 分担執筆 ,  範囲: 酸化鉄系高周波磁性体薄膜材料の開発)

    技術情報協会  2020年8月  ( ISBN:9784861047985

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    総ページ数:543p   記述言語:日本語

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  • 先端部材への応用に向けた最新粉体プロセス技術

    シーエムシー出版  2017年 

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  • 電磁波吸収・シールド材料の設計、評価技術と最新ノイズ対策

    技術情報協会  2016年  ( ISBN:9784861046

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  • Resonance-electron Mossbauer spectroscopy at low and high temperatures

    Current Topics in Crystal Growth Research (Reseach Trends, India) 

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MISC

  • 酸化物に接合された金属薄膜への分子吸着挙動

    狩野旬, 押目典宏, 廣瀬哲, 上田剛慈, 安井伸太郎, 浜嵜容丞, 伊藤満, 三上仁志, 池田直, 藤井達生, 柏原浩大, SCHNEIDER Julien

    日本物理学会講演概要集(CD-ROM)   74 ( 2 )   2019年

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  • 金属-酸化物薄膜接合系におけるエネルギーバンドアライメント

    狩野旬, 押目典宏, 廣瀬哲, 上田剛慈, 安井伸太郎, 浜嵜容丞, 伊藤満, 三上仁志, 池田直, 藤井達生, 柏原浩大, SCHNEIDER Julien

    応用物理学会秋季学術講演会講演予稿集(CD-ROM)   80th   2019年

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  • Interaction between lead-free multicomponent alkali borosilicate glass frits and hematite in red overglaze enamels

    Hirofumi Inada, Yuki Okazaki, Tadanori Yokoyama, Taigo Takaishi, Tatsuo Fujii, Jun Takada, Hidetaka Asoh, Hideki Hashimoto

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   101 ( 10 )   4538 - 4548   2018年10月

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    記述言語:英語   出版者・発行元:WILEY  

    Japanese traditional red overglaze enamel decorations on porcelain known as akae are produced using lead-containing frits, leading to a problem of lead release. Although many lead-free frits have been developed, a well-colored akae has not yet been realized, mainly because of no information on the reaction between lead-free frits and hematite during the heating process in akae production. To reveal the effect of such interaction between the frits and hematite in akae on the color tone, various akae test pieces were prepared and investigated. On using low-melting-point lead-free alkali borosilicate glass system, which contain zinc oxide, the formation of zinc ferrite proceeds simultaneously with the dissolution and particle growth of hematite in the frit melt. The particle growth rate due to dissolution and precipitation in the frit melt is faster than that due to sintering of particles caused by heat treatment of hematite powder in dry process. The dissolving capacity and promoting effect of particle growth depended on frit compositions. We also showed that the composition of akae glass layer varies because of ions diffusing from the glaze layer. Compositional changes in the akae glass could strongly affect the reactivity between the frits and hematite, resulting in variation in the color tone, the crystal phases formed, and their segregated states.

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  • Frustrated Magnetism of Pharmacosiderite Comprising Tetrahedral Clusters Arranged in the Primitive Cubic Lattice

    Ryutaro Okuma, Takeshi Yajima, Tatsuo Fujii, Mikio Takano, Zenji Hiroi

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   87 ( 9 )   093702   2018年9月

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    記述言語:英語   出版者・発行元:PHYSICAL SOC JAPAN  

    We show that pharmacosiderite is a novel cluster antiferromagnet comprising frustrated regular tetrahedra consisting of spin-5/2 Fe3+ ions arranged in the primitive cubic lattice. The connectivity of the tetrahedra and inter-cluster interaction of 2.9 K, which is significantly large compared with the intra-cluster interaction of 10.6 K, provide a unique platform for frustration physics. An unconventional antiferromagnetic order is observed below T-N similar to 6K, accompanied by a weak ferromagnetic moment and large fluctuation, as demonstrated by Mossbauer spectroscopy. A q = 0 magnetic order with a total S = 0 for the tetrahedral cluster is proposed based on an irreducible representation analysis, which may explain the origin of the weak ferromagnetism and fluctuation.

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  • Alchemy in the Art of Traditional Japanese Ceramics: Microstructure and Formation Mechanism of Gold-Colored Bizen Stoneware

    Yoshihiro Kusano, Minoru Fukuhara, Taichi Fujino, Tatsuo Fujii, Jun Takada, Mikio Takano

    CRYSTAL GROWTH & DESIGN   18 ( 7 )   4017 - 4021   2018年7月

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    記述言語:英語   出版者・発行元:AMER CHEMICAL SOC  

    The microstructure and formation process of the golden color on traditional Japanese Bizen stoneware was investigated through model experiments. The current compositional and structural research of pottery fragments has revealed that the golden color comes from Fe oxide consisting of approximately 100 nm thick agglomerates of Al-substituted hematite (alpha-(Fe1-xAlx)(2)O-3, x approximate to 0.05). The color is reproducible in the laboratory by sequential heat treatments of Bizen clay pellets under oxidizing and reducing atmospheres with an amount of potassium supplied as a melting point depressant. Lustrous colors such as silver and gold in Bizen stoneware have generally been attributed to the optical interference in superficial carbon films produced by burning wood fuel. Here, we show that the golden color is caused by the formation of Al-substituted hematite, not by the formation of carbon.

    DOI: 10.1021/acs.cgd.8b00368

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  • Pd触媒のNO‐CO反応における担体効果

    重名智博, 狩野旬, 藤井達生, 森茂生, 池田直

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   ROMBUNNO.22pPSB‐75   2018年3月

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  • Biosynthesis of Schwertmannite and Goethite in a Bioreactor with Acidophilic Fe(II)-Oxidizing Betaproteobacterium Strain GJ-E10

    Naoyuki Miyata, Ayato Takahashi, Tatsuo Fujii, Hideki Hashimoto, Jun Takada

    MINERALS   8 ( 3 )   98   2018年3月

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    記述言語:英語   出版者・発行元:MDPI  

    Iron oxide minerals, schwertmannite and goethite, which are naturally occurring in acidic environments are attractive nanostructured materials because of the potential diverse applications. Although the biosynthesis of schwertmannite by acidophilic Fe(II)-oxidizing microorganisms has been investigated, little is known about goethite biosynthesis under acidic conditions. To examine a biological approach to the synthesis of these minerals, bioreactor experiments were conducted with a newly isolated acidophilic betaproteobacterium. The bioproducts were characterized by powder X-ray diffraction, cryogenic Mossbauer spectroscopy, and electron microscopy. The cultures growing at 25 degrees C and pH 3.0 or at 37 degrees C and pH 2.5 oxidized Fe(II) and precipitated schwertmannite rapidly. Increasing pH at each temperature resulted in the concomitant production of goethite, and 90% pure goethite was obtained at 37 degrees C and pH 3.5. The goethite phase was nano-sized and had relatively large specific surface area (133 m(2).g(-1)), leading to high sorption capacity for metal oxyanions. Schwertmannite was also a good adsorbent for oxyanions, regardless of the smaller specific surface area. Our results indicate that these acidophilic microbial cultures serve as a simple rapid system for the synthesis of nanostructured goethite as well as schwertmannite.

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  • Influence of aluminum source on the color tone of cobalt blue pigment

    Mika Yoneda, Iuniaki Gotoh, Makoto Nakanishi, Tatsuo Fujii, Toshiyuki Nomura

    POWDER TECHNOLOGY   323   574 - 580   2018年1月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Cobalt blue is an inorganic pigment with an intense blue color, and consists mainly of cobalt aluminate (CoAl2O4) spinet. Many synthesis methods for cobalt blue have been reported, but there are no reports on the color tone of cobalt blue synthesized from different starting materials. Thus, the relationship between starting material and the color tone of the resulting product has not yet been clarified. We experimentally investigate the influence of different starting materials on the color tone of cobalt blue, synthesized by solid-state reaction. Cobalt oxide (Co3O4) was used as the cobalt source, and three types of aluminum source, Al(OH)(3), gamma-Al2O3, and alpha-Al2O3, were used. The color tone of cobalt blue was evaluated by the lightness L-* and Chroma 0 values, based on CIE L(*)a(*)b(*) color coordinates. The properties of the products were characterized by spectrophotometry, X-ray diffraction, scanning electron microscopy (SEM), particle size distribution analysis, and thermal gravimetric-differential thermal analyses. SEM images and particle size distribution analysis revealed that the lightness L-* value depends on the mass median diameter of the cobalt blue. The Chroma C-* value is affected by the crystallinity of the aluminum source. These results suggest that the lightness and Chroma values of cobalt blue can be controlled by the particle size and crystallinity of the starting materials. (C) 2016 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.powtec.2016.06.021

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  • Growth and charge ordering of epitaxial YbFe2O4 films on sapphire using Fe3O4 buffer layer

    Tatsuo Fujii, Tomoya Numata, Hiroki Nakahata, Makoto Nakanishi, Jun Kano, Naoshi Ikeda

    JAPANESE JOURNAL OF APPLIED PHYSICS   57 ( 1 )   010305   2018年1月

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    記述言語:英語   出版者・発行元:IOP PUBLISHING LTD  

    Well-crystallized epitaxial YbFe2O4 films were prepared on an alpha-Al2O3(001) substrate using an Fe3O4 buffer layer. Fe3O4 has a relatively small lattice mismatch with both YbFe2O4 and alpha-Al2O3. Electron diffraction analysis combined with transmission electron microscopy revealed the epitaxial relationship to be alpha-Al2O3[110](001) parallel to Fe3O4[211](111) parallel to YbFe2O4[110](001). Moreover, superlattice spots due the Fe2+-Fe3+ charge order state of YbFe2O4 were clarified. The Fe2+/Fe3+ ratio in YbFe2O4 was nearly stoichiometric. The film exhibited a ferrimagnetic transition at similar to 220K and a nonlinear current-voltage characteristic at room temperature. These results confirmed the good crystallinity and stoichiometry of the obtained YbFe2O4 films. (C) 2018 The Japan Society of Applied Physics

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  • 強誘電体BaTiO3薄膜の分極反転時における電子構造変化

    押目典宏, 狩野旬, 池永英司, 安井伸太郎, 日隈聡士, 池田直, 浜嵜容丞, 安原颯, 横谷尚睦, 伊藤満, 藤井達生, 保井晃, 大沢仁志

    応用物理学会秋季学術講演会講演予稿集(CD-ROM)   79th   2018年

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  • 分極効果で変調される強誘電体BaTiO3薄膜の電子構造

    押目典宏, 狩野旬, 狩野旬, 池永英司, 安井伸太郎, 日隈聡士, 池田直, 浜嵜容丞, 安原颯, 横谷尚睦, 伊藤満, 藤井達生, 保井晃

    日本セラミックス協会年会講演予稿集(CD-ROM)   2018   2018年

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  • Li,Al置換Y型フェライトの合成と磁気特性

    中西真, 小野紗織, 藤井達生, 菊池丈幸

    粉体および粉末冶金   64 ( 7 )   378 - 382   2017年7月

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    記述言語:日本語  

    DOI: 10.2497/jjspm.64.378

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  • Effect of dispersion and aggregation of wet-synthesized Al-substituted hematite particles on color tone of powders and red overglaze enamels

    Hirofumi Inada, Yuki Okazaki, Yuya Arakawa, Taigo Takaishi, Tatsuo Fujii, Jun Takada, Hidetaka Asoh, Hideki Hashimoto

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   125 ( 5 )   S1 - S7   2017年5月

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    記述言語:日本語   出版者・発行元:CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

    The Japanese traditional red overglaze ceramic ware, akae, a composite in which hematite particles are dispersed in a glass-frit layer, has become extremely popular with porcelain lovers all over the world. Recently, development of hematite powders dedicated to akae is strongly desired by various porcelain producers. Inspired by Fukiya bengala, a high-quality old red pigment produced in Japan in the early 18th century, we produced Al-substituted hematite powder through wet-process in a large scale. In this study, we investigated the effect of dispersion and aggregation of hematite particles on the color tone of the resultant powder, and developed a technique to produce high-quality akae using the hematite powder. The prepared powder is primarily composed of hematite nanoparticles 3 similar to 10nm in diameter that contains 5 mol% of Al3+ in the structure, and these primary particles are aggregated to form secondary particles 30-70nm in diameter. The powder showed dark brown color regardless of its nanometric character because the secondary particles form large aggregated particles with high volume fraction of hematite, leading to prevent transmission of visible light. Applying ultrasonic and silica-coating treatments that realize low volume fraction of hematite, we obtained the hematite powder exhibiting yellowish red color. In addition, high-quality akae test pieces having highly dispersive hematite particles in a glass layer were successfully prepared using ball-milling technique and subsequent combination process with the submicron-sized lead-free frit. (C) 2017 The Ceramic Society of Japan. All rights reserved.

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  • 湿式合成法で作製したAl固溶ヘマタイト粒子の分散凝集状態が粉末と赤絵の色調に及ぼす影響

    稲田博文, 岡崎友紀, 荒川裕也, 高石大吾, 藤井達生, 髙田潤, 阿相英孝, 橋本英樹

    Journal of the Ceramic Society of Japan   125 ( 5 )   S1 - S7   2017年5月

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  • Mössbauer study of zinc-substituted strontium cobalt Z-type hexaferrite

    Takeyuki Kikuchi, Masafumi Kobune, Makoto Nakanishi, Tatsuo Fujii

    Ceramics International   43   S386 - S390   2017年

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  • BaTiO3におけるバンドベンディング構造の直接観測

    押目 典宏, 狩野 旬, 池永 英司, 安井 伸太郎, 日隈 聡士, 池田 直, 横谷 尚睦, 藤井 達生

    日本物理学会講演概要集   72 ( 0 )   2725 - 2725   2017年

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    記述言語:日本語   出版者・発行元:一般社団法人 日本物理学会  

    &lt;p&gt;自発分極は試料内部の静電ポテンシャルを傾斜させる。強誘電体の原子軌道エネルギーはこの傾斜に応じて系統的に変化すると考えられる。この現象はバンドベンディングと呼ばれ40年以上に渡り予想されてきた。今回,BaTiO_3_においてバンドベンディング現象を直接的に観測したので報告する。本研究において得られた実験結果は,エピタキシャル製膜された強誘電体薄膜試料と深さ分解光電子分光実験を組み合わせることで初めて達成できた。&lt;/p&gt;

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  • 強誘電体に接合した金属微粒子の特異な価数変化II

    吉田 右, 藤井 達生, 大久保 智子, 上田 剛慈, 狩野 旬, 水牧 仁一朗, 為則 雄祐, 新田 清文, 加藤 和男, 日隈 聡士, 押目 典宏, 池田 直

    日本物理学会講演概要集   72 ( 0 )   2724 - 2724   2017年

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    記述言語:日本語   出版者・発行元:一般社団法人 日本物理学会  

    &lt;p&gt;強誘電体に金属ナノ粒子を接合させると強誘電体の分極により金属の電子状態が変調すると考えられる。電子状態変化が触媒作用に影響することが示唆されているが、電子状態異常の直接的な観測例はない。今回、強誘電体BaTiO_3_表面に担持したPdO_x_ナノ粒子に対してX線吸収微細構造(XAFS)測定を行い、粒子表面で異常な価数状態をとることを見出した、またその発現機構についての考察を行ったので報告する。&lt;/p&gt;

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  • 好酸性鉄酸化細菌を利用した鉱山廃水処理および機能性酸化鉄の生産

    宮田直幸, 東條ふゆみ, 藤井達生, 高田潤, 高田潤

    日本水環境学会年会講演集   51st   2017年

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  • BaTiO3のバンドベンディング構造

    押目典宏, 狩野旬, 狩野旬, 池永英司, 安井伸太郎, 日隈聡士, 池田直, 浜嵜容丞, 安原颯, 横谷尚睦, 伊藤満, 藤井達生, 保井晃

    応用物理学会秋季学術講演会講演予稿集(CD-ROM)   78th   2017年

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  • Bio-inspired 2-line ferrihydrite as a high-capacity and high-rate-capability anode material for lithium-ion batteries

    Hideki Hashimoto, Masahiro Ukita, Ryo Sakuma, Makoto Nakanishi, Tatsuo Fujii, Nobuyuki Imanishi, Jun Takada

    JOURNAL OF POWER SOURCES   328   503 - 509   2016年10月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    A high-capacity and high-rate-capability anode material for lithium-ion batteries, silicon-doped iron oxyhydroxide or 2-line ferrihydrite (2Fh), was prepared by mixing iron nitrate powder, tetraethyl orthosilicate, 2-propanol, and ammonium hydrogen carbonate powder at room temperature. The design of this material was inspired by a bacteriogenic product, a nanometric amorphous iron-based oxide material containing small amounts of structural Si. The atomistic structure of the prepared Si-doped 2Fh was strongly affected by the Si molar ratio [x = Si/(Fe + Si)]. Its crystallinity gradually decreased as the Si molar ratio increased, with a structural variation from nanocrystalline to amorphous at x = 0.25. The sample with x = 0.20 demonstrated the best Li storage performance. The developed material exhibited a high capacity of similar to 400 mAh g(-1) at the 25th cycle in the voltage range of 0.3-3.0 V and at a current rate of 9 A g(-1), which was three times greater than that of the Si-free 2Fh. This indicates that Si-doping into the 2Fh structure realizes good rate capability, which are presumably because of the specific nanocomposite structure of iron-based electrochemical centers embedded in the Si-based amorphous matrix, generated by reversible Li insertion/deinsertion process. (C) 2016 Elsevier B.V. All rights reserved.

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  • Quantitative study of band structure in BaTiO3 particles with vacant ionic sites

    Norihiro Oshime, Jun Kano, Naoshi Ikeda, Takashi Teranishi, Tatsuo Fujii, Takeji Ueda, Tomoko Ohkubo

    JOURNAL OF APPLIED PHYSICS   120 ( 15 )   154101 - 6   2016年10月

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    記述言語:英語   出版者・発行元:AMER INST PHYSICS  

    Levels of the conduction band minimum and the valence band maximum in ion-deficient BaTiO3 particles were investigated with optical band gap and ionization energy measurements. Though it is known that the quantification of the band structure in an insulator is difficult, due to the poor electrical conductivity of BaTiO3, systematic variation in the band energy levels was found that correlated with the introduction of vacancies. Photoelectron yield spectroscopy provided direct observation of the occupancy level of electrons, which is altered by the presence of oxygen and barium vacancies. In addition, the conduction band deviation from the vacuum level was determined by optical reflectance spectroscopy. Our results show that: (1) Introduction of oxygen vacancies forms a donor level below the conduction band. (2) The conduction band is shifted to a lower level by a larger number of oxygen vacancies, while the valence band also shifts to a lower level, due to the reduction in the density of O 2p orbitals. (3) Introduction of barium vacancies widens the band gap. Since barium vacancies can induce a small number of oxygen vacancies with accompanying charge compensation, this behavior suppresses any large formation of donor levels in the gap states, indicating that cation vacancies can control the number of both donor and acceptor levels. Published by AIP Publishing.

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  • コバルト使用量削減を目指したコバルトブルーコアシェル粒子の合成と評価

    米田 美佳, 辰己 祐哉, 野田 晃平, 後藤 邦彰, 中西 真, 藤井 達生, 野村 俊之

    粉体に関する討論会講演論文集 = Preprint of the Symposium on Powder Science and Technology   54   18 - 22   2016年9月

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    記述言語:日本語   出版者・発行元:[粉体に関する討論会]  

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  • Structural, magnetic and optical properties of YbFe2O4 films deposited by spin coating

    Tatsuo Fujii, Naoya Okamura, Hideki Hashimoto, Makoto Nakanishi, Jun Kano, Naoshi Ikeda

    AIP ADVANCES   6 ( 8 )   085213-8   2016年8月

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    記述言語:英語   出版者・発行元:AMER INST PHYSICS  

    Rare-earth iron oxides (RFe2O4) have attracting attention as new electronic device materials because of their numerous functionalities, such as electronic ferroelectricity, ferrimagnetism, and high infrared absorption. In this paper, nearly monophasic YbFe2O4 films were prepared on alpha-Al2O3 (001) substrates by the spin coating method using an aqueous-based YbFe2O4 solution. The solution was composed of a stoichiometric ratio of Yb(CH3COO)(3) and Fe(NO3)(3) with excess chelating agents. After heat treatment above 800 degrees C, well-crystallized and highly (001)-oriented YbFe2O4 started to epitaxially form on the substrate under controlled oxygen partial pressure with H-2/CO2 gas mixtures. X-ray pole figure analysis confirmed the following epitaxial relationship: YbFe2O4[100](001)//alpha-Al2O3[100](001). Moreover formation of an Fe3O4 interracial layer between YbFe2O4 and alpha-Al2O3 was detected by high-resolution transmission electron microscopy. Presence of the Fe3O4 interracial layer seemed to release the lattice misfit with the substrate. The Fe2+/Fe3+ ratio in the obtained YbFe2O4 films was nearly stoichiometric and the indirect bandgap assigned to Fe2+ -> Fe3+ charge transfer excitation was found to be similar to 0.4 eV by optical spectroscopy. A clear magnetic transition from the paramagnetic state to the ferrimagnetic state occurred at similar to 230 K. (C) 2016 Author(s).

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  • Controlling the Color of Lead-Free Red Overglaze Enamels and a Process for Preparing High-Quality Red Paints

    Hideki Hashimoto, Hirofumi Inada, Yuki Okazaki, Taigo Takaishi, Tatsuo Fujii, Jun Takada

    ACS APPLIED MATERIALS & INTERFACES   8 ( 17 )   10918 - 10928   2016年5月

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    記述言語:英語   出版者・発行元:AMER CHEMICAL SOC  

    Akae porcelain, an artistic Japanese traditional overglaze ceramic typically known for Kakiemon-style ware, has fascinated porcelain lovers around the world for over 400 years because of the graceful red color displayed by akae that matches so well with white porcelain bodies. In this work, we clarified the factors that control the color of akae and those that are conventionally controlled by artisans based on empirical experience. Inspired by a recent particle-design method, we also developed a practical facile process to prepare red paints that yields high-quality akae. Various akae samples were prepared from a combination of lead-free alkali borosilicate glass frits with different particle sizes and hematite powders with differing dispersibilities. Polarized light microscopy, scanning electron microscopy, and transmission electron microscopy analyses indicate that considering only the dispersibility of hematite powders is not sufficient, but the frit-particle size must be controlled to obtain high-quality akae with a high reflectance value for >= 580 nm visible light. In addition, we developed a process for preparing high-quality red paints that uses a large-particle frit powder and a strongly aggregated-hematite powder, both of which are easily obtainable. The red paint composed of frit, hematite, and the solvent is mixed until the paint is drying. By adding more solvent and repeating this process three times, we obtained high-quality akae with a higher reflectance value than for the akae prepared from a frit with submicron-sized particles and weakly aggregated-hematite powder. On the basis of transmission electron microscopic observations, we consider the red paint to consist of a core/shell-like composite structure of frit and hematite, forming a three-dimensional network in the akae glass layer. The good dispersibility of these particles leads to high-quality akae.

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  • BaTiO3を担体としたパラジウム微粒子の価数状態

    吉田右, 狩野旬, 押目典宏, 日隈聡士, 為則雄祐, 加藤和男, 新田清文, 水牧仁一朗, 池田直, 藤井達生, 大久保智子, 上田剛慈

    日本セラミックス協会年会講演予稿集(CD-ROM)   2016   ROMBUNNO.1P026   2016年3月

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  • Mnをドープした(YbFe2O4)m(YbFeO3)n,m=1,n=1単結晶の磁性と誘電特性

    烏谷友之, 藤原孝将, 藤井達生, 戸取和大, 古林宏之, 福永守, 堀部陽一, 狩野旬, 狩野旬, 池田直

    日本物理学会講演概要集(CD-ROM)   71 ( 1 )   2016年

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  • 21aPS-116 Mnをドープした(YbFe_2O_4)_m(YbFeO_3)_n, m=1, n=1単結晶の磁性と誘電特性

    烏谷 友之, 藤原 孝将, 藤井 達生, 戸取 和大, 古林 宏之, 福永 守, 堀部 陽一, 狩野 旬, 池田 直

    日本物理学会講演概要集   71 ( 0 )   2709 - 2709   2016年

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    記述言語:日本語   出版者・発行元:一般社団法人 日本物理学会  

    DOI: 10.11316/jpsgaiyo.71.1.0_2709

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  • 18aPS-73 BaTiO_3に接合した金属微粒子の価数異常

    吉田 右, 狩野 旬, 押目 典宏, 日隈 聡士, 加藤 和男, 新田 清文, 水牧 仁一朗, 池田 直, 藤井 達生, 大久保 智子, 上田 剛慈

    日本物理学会講演概要集   70 ( 2 )   2505 - 2505   2015年9月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

    DOI: 10.11316/jpsgaiyo.70.2.0_2505

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  • Microstructural Properties of (112¯0)-oriented Hematite-Ilmenite Solid Solution Films

    T. Fujii, T. Mino, S. Kanamaru, M. Nakanishi, H. Hashimoto, J. Takada

    Thin Solid Films   591   245 - 249   2015年9月

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  • Lithium Storage Properties of a Bioinspired 2-Line Ferrihydrite: A Silicon-Doped, Nanometric, and Amorphous Iron'Oxyhydroxide

    Hideki Hashimoto, Yuta Nishiyama, Masahiro Ukita, Ryo Sakuma, Makoto Nakanishi, Tatsuo Fujii, Jun Takada

    INORGANIC CHEMISTRY   54 ( 15 )   7593 - 7599   2015年8月

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    記述言語:英語   出版者・発行元:AMER CHEMICAL SOC  

    Inspired by a nanometric iron-based oxide material of bacterial origin, silicon (Si)-doped iron oxyhydroxide nanopartides or 2-line ferrihydrites (2Fhs) were prepared and their lithium (Li) storage properties were investigated. The structures of the Si-doped 2Fhs strongly depended on the Si molar ratio [x = Si/(Fe + Si)] whose longrange atomic ordering gradually vanished as the Si molar ratio increased, with a structural change from nanocrystalline to amorphous at x = 0.30. The most striking properties were observed for the sample with x = 0.30. Over the voltage range of 1.5-4.0 V at a current rate of 500 mA/g, this material exhibited a relatively high reversible capacity of similar to 100 mAh/g, which was four times greater than that of the Si-free 2Fh and indicated a good rate capability and cyclability. The large capacity and good rate and cycle performances are presumably because of the amorphous structure and the strong and stabilizing covalent Si-O bonds, respectively. The minor amount of Si4+ in the structure of the iron oxyhydroxides is considered to improve the electrochemical properties. Use of more appropriate doping elements and fabrication of more appropriate nanostructures could drastically improve the Li storage properties of the developed bioinspired material.

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  • Structural transformations of heat-treated bacterial iron oxide

    Hideki Hashimoto, Tatsuo Fujii, Shinji Kohara, Koji Nakanishi, Chihiro Yogi, Herwig Peterlik, Makoto Nakanishi, Jun Takada

    MATERIALS CHEMISTRY AND PHYSICS   155   67 - 75   2015年4月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE SA  

    A bacterial siliceous iron oxide microtubule (diameter: ca. 1 mu m, 15Fe(2)O(3)center dot 8SiO(2)center dot P2O6 center dot 30H(2)O) produced by Leptothrbc ochracea was heat treated in air and its structural transformation was investigated in detail by microscopy, diffractometry, and spectroscopy. Although the heat-treated bacterial iron oxide retained its original microtubular structure, its nanoscopic, middle-range, and local structures changed drastically. Upon heat treatment, nanosized pores were formed and their size changed depending on temperature. The Fe O Si linkages were gradually cleaved with increasing temperature, causing the progressive separation of Fe and Si ions into iron oxide and amorphous silicate phases, respectively. Concomitantly, global connectivity and local structure of FeO6 octahedra in the iron oxide nanoparticles systematically changed depending on temperature. These comprehensive investigations clearly revealed various structural changes of the bacterial iron oxide which is an important guideline for the future exploration of novel bio-inspired materials. (C) 2015 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.matchemphys.2015.01.067

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  • High-rate performance of a bacterial iron-oxide electrode material for lithium-ion battery

    Ryo Sakuma, Hideki Hashimoto, Genki Kobayashi, Tatsuo Fujii, Makoto Nakanishi, Ryoji Kanno, Mikio Takano, Jun Takada

    MATERIALS LETTERS   139   414 - 417   2015年1月

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    記述言語:英語   出版者・発行元:ELSEVIER  

    Lithium-ion discharge/charge properties of a nanometric amorphous iron-based oxide material of bacterial origin, L-BIOX, in a voltage range of 1.5-4.0 V were studied. X-ray absorption fine structure measurements confirmed that Fe3+ -><- Fe2+ reactions dominate in this voltage range. Cycle characteristics with a capacity exceeding 70 mAh/g at a current rate of 1670 mA/g are considerably higher than those achieved by known simple iron-oxides such as alpha-Fe2O3. (C) 2014 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.matlet.2014.10.126

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  • 好酸性鉄酸化細菌GJ-E10株が形成する酸化鉄の金属イオン吸着特性

    宮田直幸, 土門ひかる, 東條ふゆみ, 藤井達生, 橋本英樹, 高田潤, 高田潤

    日本水処理生物学会誌 別巻   ( 35 )   2015年

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  • Preparation of Yellowish-Red Al-Substituted α-Fe2O3 Powders and Their Thermostability in Color

    H. Hashimoto, M. Nakanishi, H. Asaoka, T. Maeda, Y. Kusano, T. Fujii, J. Takada

    ACS APPLIED MATERIALS & INTERFACES   6 ( 22 )   20282 - 20289   2014年11月

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  • 8pAF-11 BaTiO_3のポストアニール処理とバンド構造(8pAF 誘電体(リラクサー・酸化物系),領域10(構造物性(誘電体,格子欠陥,X線・粒子線,フォノン)))

    押目 典宏, 狩野 旬, 藤井 達生, 池田 直

    日本物理学会講演概要集   69 ( 2 )   699 - 699   2014年8月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • Bacterial Nanometric Amorphous Fe-Based Oxide: A Potential Lithium-Ion Battery Anode Material

    Hideki Hashimoto, Genki Kobayashi, Ryo Sakuma, Tatsuo Fujii, Naoaki Hayashi, Tomoko Suzuki, Ryoji Kanno, Mikio Takano, Jun Takada

    ACS APPLIED MATERIALS & INTERFACES   6 ( 8 )   5374 - 5378   2014年4月

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    記述言語:英語   出版者・発行元:AMER CHEMICAL SOC  

    Amorphous Fe3+-based oxide nanoparticles produced by Leptothrix ochracea, aquatic bacteria living worldwide, show a potential as an Fe3+/Fe-0 conversion anode material for lithium-ion batteries. The presence of minor components, Si and P, in the original nanoparticles leads to a specific electrode architecture with Fe-based electrochemical centers embedded in a Si, P-based amorphous matrix.

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  • 27pCE-8 平面四配位Ir_4As_8層を持つ鉄系超伝導体Ca_<10>(Ir_4As_8)(Fe_2As_2)_5の発見(27pCE 鉄砒素系2(合成・関連物質),領域8(強相関系))

    工藤 一貴, 光岡 大輔, 高須賀 政哉, 杉山 由季, 菅原 健人, 片山 尚幸, 澤 博, 久保 宏昭, 高森 健太, 市岡 優典, 藤井 達生, 溝川 貴司, 野原 実

    日本物理学会講演概要集   69 ( 1 )   562 - 562   2014年3月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • Characterization of microtubule material consisting of iron oxide nanoparticles produced by bacteria

    R. Sakuma, H. Hashimoto, Y. Kusano, Y. Ikeda, M. Nakanishi, T. Fujii, M. Takano, J. Takada

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   61 ( 1 )   S90 - S92   2014年

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    記述言語:英語   出版者・発行元:Journal of the Japan Society of Powder and Powder Metallurgy  

    Iron oxide microtubules produced by a species of iron-oxidizing bacteria, Leptothrix ochracea, have been expected to be useed as unique multifunctional materials such as catalysts scaffolds, pigments, and magnetic materials. However, their structural characteristics and formation mechanism are still ambiguous. The detailed features of the microtubules were characterized through electron microscopies, X-ray diffractometory, and energy dispersive X-ray spectroscopy. We found that the microtubules have hierarchical microstructures with aggregates of amorphous iron oxide nanoparticles. Statistical analysis of distributions of the tubule diameters and the wall thicknesses suggested that the tubule layer could grow from outside to inside.

    DOI: 10.2497/jjspm.61.S90

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  • Preparation and electronic properties YbFe2O4 thin films by polymerized complex method

    N. Okamura, T. Fujii, J. Takada, M. Nakanishi, J. Kano, N. Ikeda

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   61   S327 - S329   2014年

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    記述言語:英語   出版者・発行元:Journal of the Japan Society of Powder and Powder Metallurgy  

    Rare-earth iron oxides (RFe2O4) have attracting attention as new electronic device materials because of their abundant functionalities such as ferroelectricity, ferrimagnetism, and high infrared absorption. These properties are strongly related to the mixed iron valance states between Fe2+ and Fe3+. We tried to prepare RFe2O4 films by using soft chemical method. The films were prepared by spin-coating of viscous aqueous solutions of Yb(CH3COO)3 and Fe(NO3)3 with citric acid. The molar ratio between Yb:Fe was 1:2 and the citric acid: metal ratio was set to 3.75:1. After the coating, the films dried at 100�C for 10 min in air were, heat-treated at 900�C for 0.2 h in H2/CO2 gases to control oxygen partial pressure, and quenched. The obtained films were characterized by using XRD, SEM, EDS, M�ssbauer, and optical-absorption spectra. The XRD pattern clearly indicated the well-crystallized and nearly monophasic YbFe2O4 formed on the substrates above 900�C to control the oxygen partial pressure. Equal amount of Fe2+ and Fe3+ ions was present in the films. The films showed small band-gap and large optical absorbance in infrared region.

    DOI: 10.2497/jjspm.61.S327

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  • Preparation, magnetic and electric properties of (110)-oriented ordered Fe2-xTixO3 thin films

    T. Matsumoto, N. Suzuki, S. Kanamaru, H. Hashimoto, M. Nakanishi, T. Fujii, J. Takada

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   61   S330 - S332   2014年

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    記述言語:英語   出版者・発行元:Journal of the Japan Society of Powder and Powder Metallurgy  

    Ilmenite-hematite solid solution (Fe2-xTixO3) is known to have unique magnetic and electric properties. It is one of the candidates for novel magnetic semiconductors with the high Curie temperature (Tc). The carrier type of Fe2-xTixO3 is controllable by changing the Ti content x. In order to fabricate the semiconductor devices, epitaxial thin films having good crystallinity with precise control of their carrier type are required. We have already succeeded in preparing well-crystallized epitaxial Fe2-xTixO3 (x=0.7) films on α-Al2O3 (110) single-crystalline substrates by reactive helicon plasma-sputtering technique. The films are expected to have n-type conduction, while the films having the higher Ti content could be p-type conduction. In this research, we tried to prepare (110)-oriented solid solution films over a wide composition range.

    DOI: 10.2497/jjspm.61.S330

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  • 固相反応法により合成したコバルトブルーの色調に及ぼす原料混合時間と焼成温度の影響

    米田美佳, 吉田幹生, 後藤邦彰, 辻広美, 中西真, 藤井達生, 野村俊之

    粉体工学会誌   51 ( 9 )   629 - 634   2014年

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  • 好酸性鉄酸化細菌による酸化鉄生成に及ぼす培養条件の影響

    宮田直幸, 高橋安弥人, 岡野邦宏, 尾崎保夫, 藤井達生, 橋本英樹, 高田潤

    日本水処理生物学会誌 別巻   ( 33 )   58   2013年10月

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    記述言語:日本語  

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  • Superconductivity in Ca-10(Ir4As8)(Fe2As2)(5) with Square-Planar Coordination of Iridium

    Kazutaka Kudo, Daisuke Mitsuoka, Masaya Takasuga, Yuki Sugiyama, Kento Sugawara, Naoyuki Katayama, Hiroshi Sawa, Hiroaki S. Kubo, Kenta Takamori, Masanori Ichioka, Tatsuo Fujii, Takashi Mizokawa, Minoru Nohara

    SCIENTIFIC REPORTS   3   3101 - 5   2013年10月

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    記述言語:英語   出版者・発行元:NATURE PUBLISHING GROUP  

    We report the unprecedented square-planar coordination of iridium in the iron iridium arsenide Ca-10(Ir4As8)(Fe2As2)(5). This material experiences superconductivity at 16 K. X-ray photoemission spectroscopy and first-principles band calculation suggest Ir(II) oxidation state, which yields electrically conductive Ir4As8 layers. Such metallic spacer layers are thought to enhance the interlayer coupling of Fe2As2, in which superconductivity emerges, thus offering a way to control the superconducting transition temperature.

    DOI: 10.1038/srep03101

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  • Nano-Micrometer-Architectural Acidic Silica Prepared from Iron Oxide of Leptothrix ochracea Origin

    Hideki Hashimoto, Atsushi Itadani, Takayuki Kudoh, Satoshi Fukui, Yasushige Kuroda, Masaharu Seno, Yoshihiro Kusano, Yasunori Ikeda, Yasuhiko Benino, Tokuro Nanba, Makoto Nakanishi, Tatsuo Fujii, Jun Takada

    ACS APPLIED MATERIALS & INTERFACES   5 ( 11 )   5194 - 5200   2013年6月

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    記述言語:英語   出版者・発行元:AMER CHEMICAL SOC  

    We prepared nano-micrometer-architectural acidic silica from a natural amorphous iron oxide with structural silicon which is a product of the iron-oxidizing bacterium Leptothrix ochracea. The starting material was heat-treated at 500 degrees C in a H-2 gas flow leading to segregation of alpha-Fe crystalline particles and then dissolved in 1 M hydrochloric acid to remove the alpha-Fe particles, giving a gray-colored precipitate. It was determined to be amorphous silica containing some amount of iron (Si/Fe = similar to 60). The amorphous silica maintains the nano-microstructure of the starting material-similar to 1-mu m-diameter micrometer tubules consisting of inner globular and outer fibrillar structures several tens of nanometer in size and has many large pores which are most probably formed as a result of segregation of the alpha-Fe particles on the micrometer tubule wall. The smallest particle size of the amorphous silica is similar to 10 nm, and it has a large surface area of 550 m(2)/g with micropores (0.7 nm). By using pyridine vapor as a probe molecule to evaluate the active sites in the amorphous silica, we found that it has relatively strong Bronsted and Lewis acidic centers that do not desorb pyridine, even upon evacuation at 400 degrees C. The acidity of this new silica material was confirmed through representative two catalytic reactions: ring-opening reaction and Friedel-Crafts-type reaction, both of which are known to require acid catalysts.

    DOI: 10.1021/am401029r

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  • A novel route in the synthesis of magnetite nanoparticles

    Mira Ristic, Tatsuo Fujii, Hideki Hashimoto, Ivana Opacak, Svetozar Music

    MATERIALS LETTERS   100   93 - 97   2013年6月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    A novel route in the synthesis of magnetite nanoparticles is reported. This synthesis is based on autoclaving of iron choline citrate dissolved in mixed water/ethanol or water solution and neutralized with NH4OH solution. The magnetite precipitates were characterized by XRD, Mossbauer, FT-IR, HRTEM and magnetometric measurements. All the precipitated magnetite particles were in the nanosize range as shown by HRTEM. They did not contain organic residues or any other iron (hydrous) oxide phase. (C) 2013 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.matlet.2013.03.013

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  • Nano-micro-architectural composites with acid properties: Magnetic iron oxides/amorphous silicate prepared from iron oxide produced by iron-oxidizing bacterium, Leptothrix ochracea

    Hideki Hashimoto, Atsushi Itadani, Tatsuo Fujii, Makoto Nakanishi, Hiroshi Asaoka, Yoshihiro Kusano, Yasunori Ikeda, Yasushige Kuroda, Jun Takada

    MATERIALS RESEARCH BULLETIN   48 ( 3 )   1174 - 1177   2013年3月

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    記述言語:英語   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    To develop novel magnetic composites with acid functionalities, iron oxide produced by iron-oxidizing bacterium, Leptothrix ochracea, was used as a precursor. The composites were prepared by thermal treatment and subsequent reduction of the bacterial iron oxide. alpha-Fe2O3 nanoparticles obtained in air were thermally reduced to Fe3O4 and gradually oxidized to gamma-Fe2O3. The obtained composites with Fe3O4 and gamma-Fe2O3 have high magnetization values that are approximately half those of pure Fe3O4 and gamma-Fe2O3. All samples have an interesting nano-micro-architectural structure: similar to 40-nm-diameter crystalline particles covered with similar to 8-nm-thick amorphous silicate are intricately interconnected into similar to 1-mu m-diameter microtubules. Pyridine adsorption spectra indicate that the surface amorphous silicate has both Bronsted and Lewis acid properties. (c) 2012 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.materresbull.2012.12.022

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  • Acidic Amorphous Silica Prepared from Iron Oxide of Bacterial Origin

    Hideki Hashimoto, Atsushi Itadani, Takayuki Kudoh, Yasushige Kuroda, Masaharu Seno, Yoshihiro Kusano, Yasunori Ikeda, Makoto Nakanishi, Tatsuo Fujii, Jun Takada

    ACS APPLIED MATERIALS & INTERFACES   5 ( 3 )   518 - 523   2013年2月

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    記述言語:英語   出版者・発行元:AMER CHEMICAL SOC  

    Microporous and mesoporous silica derived from biogenous iron oxide is an attractive catalyst for various organic reactions. Biogenous iron oxide contains structural silicon, and amorphous silica remains after iron oxide is dissolved in concentrated hydrochloric acid. The amorphous silica containing slight amounts of iron (Si/Fe = similar to 150) is composed of similar to 6-nm-diameter granular particles. The amorphous silica has a large surface area of 540 m(2)/g with micropores (1.4 nm) and mesopores (<3 nm). By using pyridine vapor as a probe molecule to evaluate the active sites in the amorphous silica, it was found that this material has strong Bronsted and Lewis acid sites. When the catalytic performance of this material was evaluated for reactions including the ring opening of epoxides and Friedel Crafts-type alkylations, which are known to be catalyzed by acid catalysts, this material showed yields higher than those obtained with common silica materials.

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  • Crystal Structure of beta-Fe2O3 and Topotactic Phase Transformation to alpha-Fe2O3

    Teruaki Danno, Daisuke Nakatsuka, Yoshihiro Kusano, Hiroshi Asaoka, Makoto Nakanishi, Tatsuo Fujii, Yasunori Ikeda, Jun Takada

    CRYSTAL GROWTH & DESIGN   13 ( 2 )   770 - 774   2013年2月

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    記述言語:英語   出版者・発行元:AMER CHEMICAL SOC  

    beta-Fe2O3 is the scarce polymorph of Fe2O3 phases and is transformed easily into alpha-Fe2O3 at high temperature. However, its crystal structure and the transformation, mechanism to alpha-Fe2O3 are still unclear because of the difficulty in obtaining monophasic beta-Fe2O3 crystals. We established a synthesis method of the monophasic beta-Fe2O3. It was synthesized by a two-step reaction: heating a mixture of Na2SO4 and Fe-2(SO4)(3) in air at 250 degrees C to form NaFe(SO4)(2), and subsequent heating the resultant phase with NaCl in air at 500 degrees C. The crystal structure was refined to a bixbyite-type cubic structure (Ia (3) over bar) with alpha = 9.4039(1) angstrom by the Rietveld method. Single crystalline beta-Fe2O3 particles of approximately 1 mu m in size were topotactically transformed into single alpha-Fe2O3 crystals. Electron diffraction analysis revealed the crystallographic orientation relationships between beta-Fe2O3 and alpha-Fe2O3 to be [100](beta)//[0001](alpha), [010](beta)//[10 (1) over bar0](alpha), and [001](beta)//[(1) over bar2 (1) over bar0](alpha).

    DOI: 10.1021/cg301493a

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  • High-pressure synthesis, crystal structure and magnetic property of ilmenite-type FeGeO3

    Daisuke Nakatsuka, Takashi Yoshino, Jun Kano, Hideki Hashimoto, Makoto Nakanishi, Jun Takada, Tatsuo Fujii

    JOURNAL OF SOLID STATE CHEMISTRY   198   520 - 524   2013年2月

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    記述言語:英語   出版者・発行元:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    We synthesized well-crystallized ilmenite-type FeGeO3 to investigate its structural and magnetic properties. Ilmenite-type FeGeO3 were synthesized by high-pressure synthesis technique using a Kawai-type multi-anvil apparatus. Their structural and magnetic properties were examined by XRD analysis with Rietveld refinement, transmission electron microscopy, Mossbauer spectroscopy and SQUID-magnetization measurements. The subsequent annealing after the high-pressure synthesis was effective to improve the crystallinity of the ilmenite-type FeGeO3. The primary particle size of ilmenitetype FeGeO3 was similar to 15 nm. Some particles seemed to be covered with non- or poorly crystalline phase even after the annealing, and others showed a lamellar microstructure parallel to the (0 0 1) plane. Theilmenite-type FeGeO3 showed typical antiferromagnetic behavior with the Neel temperature of 79 K. (c) 2012 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.jssc.2012.11.020

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  • Amorphous structure of iron oxide of bacterial origin

    Hideki Hashimoto, Tatsuo Fujii, Shinji Kohara, Hiroshi Asaoka, Yoshihiro Kusano, Yasunori Ikeda, Makoto Nakanishi, Yasuhiko Benino, Tokuro Nanba, Jun Takada

    MATERIALS CHEMISTRY AND PHYSICS   137 ( 2 )   571 - 575   2012年12月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE SA  

    In nature, there are various iron oxides produced by the water-habitant bacterial group called "iron-oxidizing bacteria". These iron oxides have been studied mainly from biological and geochemical perspectives. Today, attempts are made to use such iron oxides as novel functional materials in several applications. However, their quantitative structural characteristics are still unclear. We studied the structure of iron oxide of microtubular form consisting of amorphous nanoparticles formed by an iron-oxidizing bacterium, Leptothrix ochracea, using a combination of high-energy X-ray diffraction and reverse Monte Carlo simulation. We found that its structure consists of a framework of corner- and edge-sharing distorted FeO6 octahedral units, while SiO4 tetrahedral units are isolated in the framework. The results reveal the atomic arrangement of iron oxide of bacterial origin, which is essential for investigating its potential as a functional material. (C) 2012 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.matchemphys.2012.10.002

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  • Synthesis and magnetic properties of magnetite-silicate nanocomposites derived from iron oxide of bacterial origin

    Hideki Hashimoto, Tatsuo Fujii, Makoto Nakanishi, Yoshihiro Kusano, Yasunori Ikeda, Jun Takada

    MATERIALS CHEMISTRY AND PHYSICS   136 ( 2-3 )   1156 - 1161   2012年10月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE SA  

    Magnetic nanocomposites containing magnetite (Fe3O4) nanoparticles were prepared from iron oxide microtubules produced by Leptothrix ochracea, a species of water-habitant iron-oxidizing bacteria. The microtubules were mainly composed of Si-containing ferric hydroxide that shows a broad X-ray diffraction pattern similar to that of 2-line ferrihydrite. After moderate heat treatment in a reductive atmosphere above 325 degrees C, the ferric ions were partially reduced to a ferrous state, and nanocrystalline Fe3O4 with a spinel-type structure was formed in a noncrystalline silicate matrix. The average crystallite size of the Fe3O4 nanoparticles was estimated to be in the order of a few nanometers. The sample heat-treated at 500 degrees C exhibited considerable magnetization together with superparamagnetic behavior at room temperature, and super-spin-glass interaction occurred at low temperature. On further heat treatment above 530 degrees C, Fe3O4 was reduced to wustite (Fe1-xO) and finally crystallized into iron metal (alpha-Fe) and ferrous silicate (Fe2SiO4). (c) 2012 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.matchemphys.2012.08.070

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  • Fabrication of novel core-shell microspheres consisting of single-walled carbon nanotubes and CaCO3 through biomimetic mineralization

    Tomoyuki Tajima, Akira Tsutsui, Tatsuo Fujii, Jun Takada, Yutaka Takaguchi

    POLYMER JOURNAL   44 ( 6 )   620 - 624   2012年6月

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    記述言語:英語   出版者・発行元:NATURE PUBLISHING GROUP  

    Calcium carbonate (CaCO3) in the presence of single-walled carbon nanotube (SWCNT) /fullerodendron supramolecular nanocomposites was crystallized with a CO2 diffusion method under ambient conditions and in aqueous environments to produce monodisperse spherical SWCNT/CaCO3 hybrids with a core-shell structure. The crystals nucleate at the carboxyl groups on the surface of the SWCNT/fullerodendron supramolecular nanocomposites grow around a spherical scaffold consisting of the SWCNTs, and finally form spherical calcite crystals embedded with and covered by the SWCNTs. Owing to of the phase transition from vaterite to calcite through a solvent-mediated process, the morphology of the microspheres is unique; the shell is primarily composed of calcite crystals of CaCO3, and a greater amount of SWCNTs is embedded in the core moiety. Polymer Journal (2012) 44, 620-624; doi:10.1038/pj.2012.36; published online 18 April 2012

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  • Biogenic manganese oxide: effective new catalyst for direct bromination of hydrocarbons

    Yuta Nishina, Hideki Hashimoto, Noriyasu Kimura, Naoyuki Miyata, Tatsuo Fujii, Bunsho Ohtani, Jun Takada

    RSC ADVANCES   2 ( 16 )   6420 - 6423   2012年

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    記述言語:英語   出版者・発行元:ROYAL SOC CHEMISTRY  

    Nano- and micro-architectural manganese oxide produced by microorganisms catalyses the selective monobromination of hydrocarbons in excellent yield under irradiation of fluorescent room light. The knowledge gained from investigating natural materials will lead to unprecedented catalyst designing toward efficient organic reactions.

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  • マンガン酸化細菌が作るマンガン酸化物~その基礎・応用研究~(1)形態的・構造的特徴について

    木村倫康, 橋本英樹, 宮田直幸, 古谷充章, 仁科勇太, 中西真, 藤井達生, 高田潤

    日本化学会講演予稿集   92nd ( 1 )   2012年

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  • 微生物由来マンガン酸化物の機能探索-磁性流体を用いた磁性の付与-

    木村倫康, 橋本英樹, SAFARIK Ivo, 仁科勇太, 宮田直幸, 中西真, 藤井達生, 高田潤

    粉体粉末冶金協会講演概要集   2012   2012年

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  • 微生物由来マンガン酸化物のキャラクタリゼーションと固体触媒への応用

    木村倫康, 橋本英樹, 仁科勇太, 宮田直幸, 古谷充章, 中西真, 藤井達生, 高田潤

    粉体粉末冶金協会講演概要集   2012   2012年

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  • Microstructure and formation conditions of the reddish hi-iro marking on traditional Japanese ceramics

    Yoshihiro Kusano, Teruaki Danno, Keiko Tokunaga, Nobuaki Kamochi, Hideki Hashimoto, Makoto Nakanishi, Tatsuo Fujii, Minoru Fukuhara, Jun Takada

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   119 ( 1396 )   942 - 946   2011年12月

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    記述言語:英語   出版者・発行元:CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

    The microstructure and conditions for the formation of the reddish color referred to as hi-iro on Japanese ceramics were investigated through model experiments. The hi-iro marking was found to be formed by the reaction between clay and alkali ions supplied from the glaze. When a mixture of porcelain clay and 20 wt % KCl was heated in air at 1250 degrees C and then cooled slowly to 800 degrees C, hi-iro clearly appeared on the sample surface. In hi-iro, corundum [alpha-(Al,Fe)(2)O-3], hematite (alpha-Fe2O3) and a liquid phase are formed. Upon heating until 1250 degrees C, corundum is firstly precipitated as hexagonal plate-like crystals. During the cooling process, hematite precipitates on the edges of the corundum crystals to form specific composite particles. When rapidly cooled from 1250 degrees C to room temperature, a brownish red color appeared on the sample surface, which was found to be caused by the formation of approximately 50 mu m Al-substituted hematite (Fe1.9Al0.1O3) particles. The relationship between the microstructure of the phases formed and the color is discussed. (C)2011 The Ceramic Society of Japan. All rights reserved.

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  • Synthesis and anomalous magnetic properties of LaFeO3 nanoparticles by hot soap method

    Tatsuo Fujii, Ikkoh Matsusue, Daisuke Nakatsuka, Makoto Nakanishi, Jun Takada

    MATERIALS CHEMISTRY AND PHYSICS   129 ( 3 )   805 - 809   2011年10月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE SA  

    Nanocrystalline LaFeO3 particles were synthesized at low temperatures by using hot soap technique. The synthesis was based on the thermal decomposition of organometallic compounds precipitated in a hot coordinating solvent. Moderate heat treatment at low temperature far below the combustion point of organic compounds produced spherical LaFeO3 nanoparticles with average diameter of about 15 nm. The crystalline phase, structure and particle size of obtained products were characterized by Xray diffraction, infrared spectroscopy and transmission electron microscopy observations. In spite of the antiferromagnetic nature of bulk LaFeO3, the obtained nanoparticles exhibited anomalous large magnetization. Superparamagnetic behavior with a blocking temperature of about 30 K was observed in both magnetization and Mossbauer spectroscopic analyses. (C) 2011 Elsevier B.V. All rights reserved.

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  • 23aJA-4 X線発光分光法を用いた吸収端評価(23aJA X線・粒子線(X線),領域10(誘電体,格子欠陥,X線・粒子線,フォノン))

    伊藤 嘉昭, 重岡 伸之, 大橋 浩史, 栃尾 達紀, 福島 整, 寺澤 倫孝, 藤井 達生, 蔭山 博之, 吉井 賢資, 米田 安宏, 二澤 宏司

    日本物理学会講演概要集   66 ( 2 )   1001 - 1001   2011年8月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • Synthesis of single-phase Sr3Co2Fe24O41 Z-type ferrite by polymerizable complex method

    Takeyuki Kikuchi, Tatsuya Nakamura, Tohru Yamasaki, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Yasunori Ikeda

    MATERIALS RESEARCH BULLETIN   46 ( 7 )   1085 - 1087   2011年7月

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    記述言語:英語   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Synthesis of single-phase Sr3Co2Fe24O41 Z-type (Sr(3)CO(2)Z) ferrite was realized by adopting the polymerizable complex method. Crystal structure of samples has been investigated by powder X-ray diffraction (XRD). Single-phase Sr(3)Co(2)Z ferrite was obtained by heating at 1473 K for 5 h in air. Magnetic properties were discussed by measurements of M-H curves with vibrating sample magnetometer (VSM). Sr(3)CO(2)Z ferrite prepared by polymerizable complex method showed typical M-H curve of soft ferrite, with a saturation magnetization of 21.5 mu(B)/formula unit (50.5 emu/g) and a coercive force of 0.0141 at room temperature. (C) 2011 Elsevier Ltd. All rights reserved.

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  • Speculations on anomalous chemical states of Ti ions in FeTiO3 observed by high-resolution X-ray K beta emission spectra

    Tatsuo Fujii, Hirofumi Oohashi, Tatsunori Tochio, Yoshiaki Ito, Aurel-Mihai Vlaicu, Sei Fukushim

    JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA   184 ( 1-2 )   10 - 15   2011年2月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    A series of high-resolution Ti K beta X-ray emission spectra were measured for various isomorphous titanium oxides with composition MTiO3, where M was divalent Mg, Mn, Fe, Co, or Ni. The detailed spectral features of Ti K beta lines for MTiO3 were intermediate between those of TiO2 and Ti2O3 depending on the coexisting cation species M, though the formal valence states of all Ti ions in MTiO3 were consistent with those in TiO2. Especially in the case of FeTiO3, the features in both main and satellite lines had many similarities of Ti2O3. The Ti K beta X-rays of FeTiO3 seemed to be emitted by the transition from Ti3+-like states. Because of the small difference in energies and the large overlap between Ti 3d and Fe 3d orbitals, intermediate core-hole states occurring on the X-ray emission process might produce the inter-valence charge transfer from Fe2+ to Ti4+ to form the Ti3+-like states. The DV X alpha calculations based on the molecular orbital theory can reproduce the satellite structures to assume the increasing 3d electron densities on Ti for FeTiO3. (C) 2010 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.elspec.2010.10.003

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  • Anomalous hydrogen absorption on non-stoichiometric iron-carbon compound

    Hiroki Miyaoka, Takayuki Ichikawa, Tatsuo Fujii, Wataru Ishida, Shigehito Isobe, Hironobu Fuji, Yoshitsugu Kojima

    Journal of Alloys and Compounds   507 ( 2 )   547 - 550   2010年10月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE SA  

    On the synthesis of nano-structural hydrogenated graphite by ball-milling under H atmosphere, iron contamination was mingled from steel balls during ball-milling. It is clarified by spectroscopic measurements that the mingled iron formed a non-stoichiometric iron-carbon (Fe-C) compound. The Fe-C phase was transformed to a well-ordered phase with H desorption at 450 °C, suggesting that the hydrogen atoms were anomalously trapped at the Fe-C phase. With respect to hydrogen absorbing properties, the mingled iron enhanced the hydrogen capacity by about 50% compared with iron free hydrogenated graphite, where H/Fe was about 13 mass%. Therefore, if the hydrogen absorption site originated in the Fe-C phase could be synthesized independently, it should be recognized as a promising hydrogen storage system. © 2010 Elsevier B.V. All rights reserved. 2 2

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  • Magnetic properties of La-Co substituted M-type strontium hexaferrites prepared by polymerizable complex method

    Takeyuki Kikuchi, Tatsuya Nakamura, Tohru Yamasaki, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Yasunori Ikeda

    Journal of Magnetism and Magnetic Materials   322 ( 16 )   2381 - 2385   2010年8月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Magnetic properties of La-Co substituted M-type strontium hexaferrites were studied. The samples were prepared by polymerizable complex method. Crystal structure of samples has been investigated by powder X-ray diffraction (XRD). Single-phase M-type strontium hexaferrites with chemical composition of Sr La Fe Co O (x=0-0.4) were formed by heating at 1173 K for 24 h in air. Magnetic properties were discussed by measurements of M-H curves with vibrating sample magnetometer (VSM). La-Co substituted M-type strontium hexaferrites prepared by polymerizable complex method showed typical magnetic hysteresis of hard ferrite. The coercive force increased significantly by La-Co substitution with polymerizable complex method. Maximum coercive force achieved in this study is 8.0 kOe (640 kA/m). Scanning electron microscopy revealed that the prepared ferrite particles have plate-like shape of diameter range between 20 and 500 nm. © 2010 Elsevier B.V. All rights reserved. 1.05-x x 12-x x 19

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  • 20pPSA-51 Fe_2O_3-FeTiO_3固溶体薄膜の電気伝導特性(20pPSA 領域8ポスターセッション(低温II(Cu,Ru,Mn,Co酸化物など,磁束量子系)),領域8(強相関系:高温超伝導,強相関f電子系など))

    味野 朋裕, 土井 善文, 中西 真, 藤井 達生, 高田 潤

    日本物理学会講演概要集   65 ( 1 )   576 - 576   2010年3月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • 22pPSA-1 元素置換イルメナイトFeM_xTi_<1-x>O_3の構造と磁性(22pPSA 領域3ポスターセッション(酸化物・f電子系磁性・スピングラス・量子スピン・フラストレーション系・実験技術・磁性一般),領域3(磁性,磁気共鳴))

    中塚 大輔, 藤井 達生, 中西 真, 高田 潤

    日本物理学会講演概要集   65 ( 1 )   498 - 498   2010年3月

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  • Synthesis and characterization of new iron(III) layered hydroxides

    Tsutomu Katamoto, Hideki Hashimoto, Tatsuo Fujii, Jun Takada

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   57 ( 2 )   76 - 83   2010年2月

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    記述言語:日本語  

    A new layered iron hydroxide was synthesized by a wet chemical technique, by which aqueous ferrous sulfate solution was gradually oxidized by using sodium carbonate at 283 ∼ 333 K. Obtained yellowish precipitates identified by X-ray powder diffraction had a similar structure to the layered double hydroxides. The observed interlayer spacing was about d=0.74 nm. Electron micrographs showed that the particles had plate-like morphology. Electron diffraction pattern of the plate-like particles had hexagonal symmetry, when the electron beam was aligned normal to the planes. Mössbauer spectrum suggested that all iron ions were paramagnetic Fe states with large quadrupole splittings at room temperature. These results show that the obtained new layered iron hydroxide cotains only Fe(III) ion species. Water vapor adsorption curves of the sample oxidized át 291 K showed high adsorption value (19 wt%) by unit weight. 3+

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  • Fe(III)系新規層状含水酸化物の合成とキャラクタリゼーション(共著)

    片元勉, 橋本英樹, 藤井達生, 高田潤

    粉体および粉末冶金   57 ( 2 )   76 - 83   2010年2月

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    記述言語:日本語  

    DOI: 10.2497/jjspm.57.76

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  • Structure and magnetic properties of Fe<inf>2</inf>O<inf>3</inf>-FeTiO <inf>3</inf> films

    Tatsuo Fujii, Tatsuya Sugano, Makoto Nakanishi, Jun Takada

    Journal of Physics: Conference Series   200 ( SECTION 7 )   072029-1-4   2010年

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    記述言語:英語   出版者・発行元:IOP PUBLISHING LTD  

    Solid solutions between ilmenite (FeTiO ) and hematite (α-Fe O ) are one of the candidates for high-temperature magnetic semiconductors. Well-crystallized epitaxial xFeTiO -(1-x)Fe O (0.5<x<1) films were prepared on both α-Al O (001) and (110) single-crystalline substrates by reactive sputtering technique. The (110)-oriented films provided more restricted preparation conditions than the (001)-oriented ones. Both films with x<0.7 had large saturation magnetization at room temperature. The magnetic easy plane lay in the (001) crystallographic plane regardless of the film orientations. The magnetic properties of (001)- and (110)-oriented films seemed to be affected not only by the crystalline orientation but also by the lattice strains induced in the films. © 2010 IOP Publishing Ltd. 3 2 3 3 2 3 2 3

    DOI: 10.1088/1742-6596/200/7/072029

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  • Chemical modification of biogenous iron oxide to create an excellent enzyme scaffold

    Takashi Sakai, Yuki Miyazaki, Ai Murakami, Noriko Sakamoto, Tadashi Ema, Hideki Hashimoto, Mitsuaki Furutani, Makoto Nakanishi, Tatsuo Fujii, Jun Takada

    Organic and Biomolecular Chemistry   8 ( 2 )   336 - 338   2010年

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    記述言語:英語   出版者・発行元:ROYAL SOC CHEMISTRY  

    The biogenous iron oxide (BIO) from Leptothrix ochracea was transformed to an organic-inorganic hybrid support to prepare an excellent immobilized enzyme showing high catalytic performance. © 2010 The Royal Society of Chemistry.

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  • 27pPSA-57 Ge置換FeTiO_3の構造と磁性(領域3ポスターセッション(量子スピン系・フラストレーション系等),領域3,磁性,磁気共鳴)

    中塚 大輔, 藤井 達生, 中西 真, 高田 潤

    日本物理学会講演概要集   64 ( 2 )   394 - 394   2009年8月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • 27pYD-11 酸化鉄化合物/C60接合系におけるPN接合と光学特性(界面・分子デバイス3,領域7,分子性固体・有機導体)

    永田 知子, 浜尾 志乃, 高橋 庸祐, 真栄田 大介, 河相 暢幸, 佐坂 英信, 久保園 芳博, 明渡 純, 朴 載赫, 藤井 達生, 神戸 高志, 池田 直

    日本物理学会講演概要集   64 ( 2 )   780 - 780   2009年8月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • Effects of rice straw on the color and microstructure of bizen, a traditional japanese stoneware, as a function of oxygen partial pressure

    Yoshihiro Kusano, Akira Doi, Minoru Fukuhara, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Yasunori Ikeda, Mikio Takano, Catherine Henrist, Rudi Cloots, André Rulmont, Marcel Ausloos

    Journal of the American Ceramic Society   92 ( 8 )   1840 - 1844   2009年8月

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    記述言語:英語   出版者・発行元:WILEY  

    The effects of oxygen partial pressure during thermal treatment on the color and microstructure of Bizen, a traditional Japanese stoneware, were studied through model experiments using clay pellets covered lightly with rice straw as a coloring assistant. When heated in flowing nitrogen, the model pellet turned blackish owing to the formation of α-Fe particles coated with graphite. However, schreibersite (Fe P), which is also blackish, was formed specifically on the pellet surface in direct contact with the straw. The rice straw seems to have generated a strongly reducing atmosphere, strong enough for the metallization to α-Fe, and also to have provided phosphorus through contact. When oxygen content in the surrounding gas atmosphere was raised to N /O =99/1, the pellet surface turned yellowish brown because the main coloring material was Fe -containing mullite. At oxygen contents of N /O =98/2 or more, the formtion of hematite (α-Fe O ) pushed the color to deep red. © 2009 The American Ceramic Society. 3 2 2 2 2 2 3 3+

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  • Synthesis and magnetic properties of AgI intercalated Bi-Ca-Co-O misfit-layer cobalt oxide

    Y. Tanaka, T. Fujii, M. Nakanishi, Y. Kusano, Y. Ikeda, J. Takada

    Materials Letters   63 ( 2 )   328 - 330   2009年1月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    We report the synthesis and magnetic properties of the AgI-intercalated misfit-layer cobalt oxide Bi Ca Co O . The AgI-intercalated Bi Ca Co O was prepared by the guest exchange reaction from the I -intercalated one. SEM-EDX analysis exhibited the stoichiometric ratio of Ag/I and the guest concentration as (AgI)Bi Ca Co O on the basis of Co = 2. After the AgI intercalation, the lattice parameter along the c-axis calculated from X-ray diffraction patterns was 21.68 Å, which was drastically increased not only from the non intercalated host phase (14.68 Å) but also from the I -intercalated phase (18.08 Å). After the AgI intercalation, magnetic susceptibility measurements revealed that the antiferromagnetic Weiss temperature and the effective magnetic moment in Co ion simultaneously decreased compared with the non-intercalated host compound. © 2008 Elsevier B.V. All rights reserved. 1.8 2 2 z 1.8 2 2 z 2 1.8 2 2 z 2

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  • Erratum to "Characteristics of hollow microtubes consisting of amorphous iron oxide nanoparticles produced by iron oxidizing bacteria, Leptothrix ochracea". [J. Magn. Magn. Mater. 310 (2007) 2405-2407] (DOI:10.1016/j.jmmm.2006.10.793)

    H. Hashimoto, S. Yokoyama, H. Asaoka, Y. Kusano, Y. Ikeda, M. Seno, J. Takada, T. Fujii, M. Nakanishi, R. Murakami

    Journal of Magnetism and Magnetic Materials   320 ( 18 )   2310 - 2310   2008年9月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    DOI: 10.1016/j.jmmm.2008.01.046

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  • 21pPSA-8 Fe_<2-x> Ti_xO_3(001)及び(110)配向膜の作製と物性(21pPSA 領域3ポスターセッション,領域3(磁性,磁気共鳴))

    菅野 達也, 高田 裕輔, 藤井 達生, 中西 真, 高田 潤

    日本物理学会講演概要集   63 ( 2 )   386 - 386   2008年8月

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  • 21pPSA-59 Ge置換FeTiO_3の合成と物性(21pPSA 領域3ポスターセッション,領域3(磁性,磁気共鳴))

    中塚 大輔, 藤井 達生, 中西 真, 高田 潤

    日本物理学会講演概要集   63 ( 2 )   399 - 399   2008年8月

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  • Electronic structure of stoichiometric and non-stoichiometric epitaxial FeTiO<inf>3+δ</inf> films

    T. Fujii, Y. Takada, M. Nakanishi, J. Takada, M. Kimura, H. Yoshikawa

    Journal of Physics: Conference Series   100 ( 1 )   12043-1-4   2008年3月

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    記述言語:英語   出版者・発行元:IOP PUBLISHING LTD  

    Well-crystallized epitaxial FeTiO films were prepared on the sapphire substrate by reactive sputtering technique. A wide range of oxygen nonstoichiometry from FeTiO to FeTiO was successfully controlled by controlling the sputtering conditions. All films had uniform structure without phase separation even for the highly oxidized FeTiO film. Structures, magnetic and electronic properties of the FeTiO films were seriously influenced by the oxygen nonstoichiometry. The nearly stoichiometric FeTiO films had a R structure, while the nonstoichiometric FeTiO had a R c structure. With increasing the oxygen nonstoichiometry, the valence states of Fe ions in FeTiO were examined to be changed from Fe to Fe by means of both Mössbauer and XPS spectroscopy. The Ti 2p core-level XPS spectra clearly confirmed the valence states of Ti ions in nonstoichiometric FeTiO . However the Ti ions in stoichiometric FeTiO suggested the abundant electron density than the conventional Ti ions due to the Fe to Ti intervalence charge transfer. © 2008 IOP Publishing Ltd. 3+δ 3 3.5 3.5 3+δ 3 3.5 3+δ 3.5 3 2+ 3+ 4+ 4+ 2+ 4+

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  • Epitaxial growth of ε-Fe2O3 on mullite found through studies on a traditional Japanese stoneware

    Y. Kusano, T. Fujii, J. Takada, M. Fukuhara, A. Doi, Y. Ikeda, M. Takano

    Chemistry of Materials   20 ( 1 )   151 - 156   2008年1月

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  • Structural and magnetic ordering in the V<inf>x</inf>Nb<inf>1+y</inf>S<inf>2</inf> system

    Makoto Nakanishi, Yukiyasu Matsuno, Tatsuo Fujii, Jun Takada, Kazuyoshi Yoshimura

    Journal of Physics and Chemistry of Solids   69 ( 1 )   49 - 54   2008年1月

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    記述言語:英語   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    The influence of composition on the structural ordering and magnetism in the V Nb S system has been investigated by X-ray diffraction and magnetic measurements. Stoichiometric V NbS did not exhibit the structural ordering of vanadium between the NbS layers. In the ordered structure, the vanadium composition deviated from the ideal value of x = frac(1, 3) to both higher and lower values, while the niobium composition was in the range of 0.05≤y≤0.18. Excess niobium, y>0, is thought to play an essential role in the structural ordering in this system. For samples with excess niobium and ordered structures, a magnetic transition was observed at 20-50 K, depending on the composition. The spontaneous magnetization of 3-5×10 μ /V atom is thought to be intrinsic to this system. The magnetization curves consisted of a constant and a proportional parts of the magnetic field, which correspond to the spontaneous magnetization and high-field susceptibility, respectively. The magnetization curves and the temperature dependencies of the high-field susceptibility were quite similar to those of the canted antiferromagnetic NiS . A correlation between the structural and magnetic ordering is suggested. © 2007 Elsevier Ltd. All rights reserved. x 1+y 2 1/3 2 2 B 2 -3

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  • Preparation and characterization of epitaxial Fe2-x Tix O3 films with various Ti concentrations (0.5&lt;x&lt;1.0)

    Y. Takada, M. Nakanishi, T. Fujii, J. Takada, Y. Muraoka

    Journal of Applied Physics   104 ( 3 )   33713-1-5   2008年

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    記述言語:英語   出版者・発行元:AMER INST PHYSICS  

    An ilmenite-hematite solid solution (Fe2-x Tix O3) is one of the candidates for practical magnetic semiconductors with a high Curie temperature. We have prepared well-crystallized epitaxial Fe2-x Tix O3 films with a wide range of Ti concentrations- x=0.50, 0.60, 0.65, 0.76, 0.87, and 0.94-on α -Al2 O3 (001) substrates. The films are prepared by a reactive helicon plasma sputtering technique to evaporate Fe and TiO targets simultaneously under optimized oxygen pressure conditions. The structural characterizations of the films reveal that all films have a single phase of the ordered structure with R 3- symmetry, where Ti-rich and Fe-rich layers are stacked alternately along the c axis. All films have large ferrimagnetic moments at low temperature, and room temperature magnetization is clearly observed at x<0.7. The inverse temperature dependence of the resistivities of the films indicates their semiconducting behavior. The film resistivities decrease with decreasing Ti concentration. © 2008 American Institute of Physics.

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  • Preparation and characterization of (001)- and (110)-oriented 0.6FeTiO3・0.4Fe2O3 films for room temperature magnetic semiconductors

    Y. Takada, M, Nakanishi T, Fujii J. Takada

    APPLIED PHYSICS LETTERS   92 ( 25 )   252102-1-3   2008年

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  • Epitaxial growth of epsilon iron oxide on mullite found through studies on traditional Japanese stoneware

    Yoshihiro Kusano, Tatsuo Fujii, Jun Takada, Minoru Fukuhara, Kazuhiro Yamaguchi, Kenji Takabatake, Akira Doi, Yasunori Iked, Mikio Takano

    A Global Road Map for Ceramic Materials and Technologies: Forecasting the Future of Ceramics, International Ceramic Federation - 2nd International Congress on Ceramics, ICC 2008, Final Programme   4-P-052-1-4-P-052-5   2008年

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    On traditional Japanese stoneware called "Bizen", we found that ε-Fe O crystallizes epitaxially on needle-like mullite crystals. This interesting reaction occurred when a pellet of Bizen clay powder was heated with rice straw to 1250°C in a stream of N containing 1∼2 vol% of O . It is known that mullite forms from the clay on heating and that the rice straw provides potassium to induce partial melting in the pellet surface. The ε-Fe O -on- mullite particles formed in this molten region, changing their morphology and the relative ε-Fe O -to-mullite orientation with oxygen partial pressure. This discovery suggests morphological controllability of ε-Fe O as a function of oxygen partial pressure. 2 3 2 2 2 3 2 3 2 3

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  • 備前焼「緋襷模様」とベンガラ -炎と酸化鉄が織り成す芸術-

    草野圭弘, 藤井達生, 高田潤

    固体物理   43 ( 5 )   303 - 314   2008年

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    記述言語:日本語   出版者・発行元:アグネ技術センタ-  

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  • Morphological and microstructural study of iron oxide microtubes formed by iron oxidizing bacteria, Leptothrix ochracea

    H. Hashimoto, S. Yokoyama, H. Asaoka, Y. Kusano, Y. Ikeda, M. Seno, J. Takada, T. Fujii, M. Nakanishi, R. Murakami

    A Global Road Map for Ceramic Materials and Technologies: Forecasting the Future of Ceramics, International Ceramic Federation - 2nd International Congress on Ceramics, ICC 2008, Final Programme   6-P-011-1-6-P-011-4   2008年

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    Characterization of biogenic iron oxide sheaths produced by Leptothrix ochracea (L. ochracea) was investigated. The sheaths had average inner- and outer-diameters of 1.08 ± 0.15 and 1.35 ± 0.14 μm, respectively. Their length ranged from 10-2000 μm. Outer and inner surface of each sheath were composed of fibrous and spherical particles, respectively. The width of fibrous particles was approx. 20 nm, while the diameter of spherical particles was 20-120 nm. The chemical composition of the sheaths was Fe: Si: P = 73: 22: 5 with the exception of H and O. The sheaths had similar structure to that of 2-line ferrihydrite.

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  • Preparation and characterization of (001) and (110)-oriented fe <inf>1.4</inf>Ti<inf>0.6</inf>O<inf>3</inf> films

    Tatsuo Fujii, Tatsuya Sugano, Yusuke Takada, Makoto Nakanishi, Jun Takada

    Materials Research Society Symposium Proceedings   1119   7 - 12   2008年

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    Thin films of ilmenite-hematite solid solution, Fe Ti O were prepared on α-A1 O (001) and (110) single-crystalline substrates by reactive helicon plasma-sputtering technique. The oxide phases formed in the thin films and the degree of cation ordering in the ilmenite phase strongly depended on the preparation conditions. At the optimized preparation conditions, regardless of the substrate orientation, well-ordered Fe Ti O films with R3 symmetry were epitaxially formed on the substrates. Large saturation magnetization at room temperature was observed in both (001)- and (110)-oriented films. The ordered Fe Ti O films were ferrimagnetic semiconductors at room temperature. The (110)-oriented film had uniaxial in-plane magnetic and electric anisotropies, because Fe Ti O had a magnetic easy plane and predominant conduction in the (001) crystallographic plane. The differences in magnetization and electrical resistivity curves between the (001)- and (110)-oriented films indicated the anisotropic nature of Fe Ti O . 1.4 0.6 3 2 3 1.4 0.6 3 1.4 0.6 3 1.4 0.6 3 1.4 0.6 3

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  • Synthesis, morphology and color tone properties of the lanthanum substituted hematite

    T. I. Bhuiyan, M. Nakanishi, Y. Kusano, T. Fujii, J. Takada, Y. Ikeda

    Materials Letters   61 ( 17 )   3774 - 3777   2007年7月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    The polymeric complex method has been employed to investigate the effects of substitution by lanthanum into hematite powder on structures, morphology and color tone properties. X-ray diffraction measurements evidenced the existence of Fe La O at 1000 °C-1200 °C by shifting peaks to lower angles. At higher temperature, lattice parameters and cell volume were found to expand due to the incorporation of La ion into the hematite in the range 301.98-303.87 Å . Crystalline size decreased when increasing the amount of La ion in the reaction process. Suppression of particle growth was observed by the Field Emission Scanning Electron Microscopy studies at higher temperatures. Brighter yellowish-red color than that of pure hematite was obtained and it grew into deeper color tone rapidly by increasing the amount of La ion into the hematite. © 2007. 2 - x x 3 3+ 3 3+ 3+

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  • Preparation and characterization of ilmenite-hematite thin films

    Y. Takada, M. Nakanishi, T. Fujii, J. Takada

    Journal of Magnetism and Magnetic Materials   310 ( 2 SUPPL. PART 3 )   2108 - 2110   2007年3月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Ilmenite-hematite solid solution (Fe Ti O ) is one of the candidates for practical magnetic semiconductors with the high Curie temperature (T ). We have successfully prepared well-crystallized and epitaxial Fe Ti O films by using a reactive helicon plasma sputtering technique. The structural characterizations indicated that the films had the order structure (R over(3, -) symmetry), where Ti- and Fe-rich layers were stacked alternately along the c-axis, without any secondary phase. The subsequent annealing of the films in vacuum at 700 °C promoted the R over(3, -) symmetry. Only the films having the good R over(3, -) symmetry had large ferrimagnetic moments at room temperature. The resistivities of the films clearly showed semiconducting behavior, i.e., logarithmic resistivity showed a monotonous increase with increasing the inverse temperature. The minimum room temperature resistivity of the films was about 10 Ω cm. From the Hall effect measurement all films had n-type conduction. The carrier concentration was estimated to be about 10 -10 cm , depending on the annealing conditions. © 2006 Elsevier B.V. All rights reserved. 2-x x 3 C 1.4 0.6 3 -1 19 21 -3

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  • Characteristics of hollow microtubes consisting of amorphous iron oxide nanoparticles produced by iron oxidizing bacteria, Leptothrix ochracea

    H. Hashimoto, S. Yokoyama, H. Asaoka, Y. Kusano, Y. Ikeda, M. Seno, J. Takada, T. Fujii, M. Nakanishi, R. Murakami

    Journal of Magnetism and Magnetic Materials   310 ( 2 SUPPL. PART 3 )   2405 - 2407   2007年3月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Some features of characteristic iron oxide sheaths which the iron oxidizing bacteria Leptothrix ochracea (L. oceracea) formed were studied in order to make clear their morphology microstructure, chemical composition, and crystal structure through scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), and X-ray diffraction (XRD). Each sheath was a hollow tube with average outer and inner diameters of 1.1 and 1.4 μm, respectively. Their length ranged from 10 to 200 μm and the aspect ratio was 10-200. Each sheath was constructed by very small particles with a diameter of less than 100 nm. The hollow sheaths were mainly composed of Fe and O with small amounts of Si and P. The chemical composition analyzed by EDX was roughly Fe:Si:P=80:15:5 with the exception of O. XRD measurement revealed that crystal structures of the sheath were similar to that of 2-line ferrihydrite. The sheath showed spin-glass-like magnetic properties. © 2006 Elsevier B.V. All rights reserved.

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  • Large magnetic polarization of Ti4+ ions in FeTiO<inf>3</inf>

    T. Fujii, M. Yamashita, S. Fujimori, Y. Saitoh, T. Nakamura, K. Kobayashi, J. Takada

    Journal of Magnetism and Magnetic Materials   310 ( 2 SUPPL. PART 2 )   E555 - E557   2007年3月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Nominal valence states of Ti ions in FeTiO are generally considered to be Ti . However, due to the close energy levels between Fe and Ti states, there are some possibilities of intervalence charge transfer from Fe to Ti . In order to clarify the real electronic structures of Ti ions in FeTiO , we performed resonant photoemission spectroscopy (RPES) and X-ray magnetic circular dichroism (XMCD) across the Ti 2p→3d excitation. The RPES spectra clearly indicated the partial density of states derived from the Ti 3d states on the valence band. The Ti 3d states appearing at the top of the valence bands were overlapped with the Fe 3d states. Moreover, the XMCD spectra at Ti L edges suggested large magnetic polarization of Ti ions in FeTiO in spite of nonmagnetic natures of Ti ions in common sense. The Ti ions in FeTiO seemed to have some 3d electron densities caused by the electron transfer from the Fe 3d t ↓ states. © 2006 Elsevier B.V. All rights reserved. 3 3 2,3 3 3 2g 4+ 2+ 4+ 2+ 4+ 4+

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  • Synthesis, structures and properties of the cerium doped hematite co-existing with CeO<inf>2</inf>

    Tarequl Islam Bhuiyan, Makoto Nakanishi, Yoshihiro Kusano, Tatsuo Fujii, Jun Takada, Yasunori Ikeda

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   54 ( 2 )   112 - 118   2007年2月

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    記述言語:日本語  

    Cerium doped hematite powders obtained by polymeric complex method following the hydrolysis of FeCl · 6H O and Ce(NH ) (NO )6. X-ray diffraction pattern of cerium doped samples obtained at 1000°C̃ 1200°C for two hours in air revealed some solubility of cerium ion in α-Fe O over the composition range of 5%̃15 at% that were characterized by the shifting of X-ray diffraction peaks compared with the internal silicon standard. X-ray Photoelectron Spectra investigations revealed the existence of Ce ion at higher temperature. Unit cell parameters were found to expand due to the incorporation of cerium ions into the hematite lattice. Field Emission Scanning Electron Microscopy studies showed that the growth of particles was suppressed in the appearance of cerium ions into the α-Fe O lattice. Fe Ce O exhibits much lower magnetization due to the incorporation of non-magnetic cerium ions into the α-Fe O . Spectroscopy measurement evidenced that cerium doped hematite samples exhibited brighter yellowish red color tone than that of pure α-Fe O . 3 2 4 2 3 2 3 3+ 2 3 2-x x 3 2 3 2 3

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  • Systematic study on synthesis and structural, electrical transport and magnetic properties of Pb-substituted Bi-Ca-Co-O misfit-layer cobaltites

    Yoshiaki Tanaka, Tatsuo Fujii, Makoto Nakanishi, Yoshihiro Kusano, Hideki Hashimoto, Yasunori Ikeda, Jun Takada

    Solid State Communications   141 ( 3 )   122 - 126   2007年1月

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    記述言語:英語   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Single-phases of Pb-substituted Bi-Ca-Co-O misfit-layer cobaltites with various Pb concentrations have been synthesized and the Pb-substitution effects on the structural, electrical and magnetic properties have been systematically investigated. Powder X-ray diffraction analysis showed that the single-phases of Bi Pb Ca Co O were obtained up to x = 0.6 - 0.7 under the optimized synthesis conditions. The lattice parameters of Bi Pb Ca Co O continuously changed with increasing Pb concentration. The electron diffraction analysis suggested that the structure consisted of two different sublattices with a rock salt structure (RS) and a hexagonal CdI structure (H), respectively, without modulation. In combined with the chemical composition analysis, the chemical formulas of the x = 0 and x = 0.6 samples were determined approximately as [Bi Co Ca O ] [CoO ] and [Bi Pb Co Ca O ] [CoO ] , respectively. The electrical resistivity became more metallic with increasing the Pb concentration up to x = 0.6. Moreover, the Pb-substitution simultaneously increased the antiferromagnetic Weiss temperatures and decreased the effective magnetic moments of the Co ions. © 2006 Elsevier Ltd. All rights reserved. 1.8-x/2 x 2 2 z 1.8-x/2 x 2 2 z 2 1.74 0.31 2.01 4 2 1.69 1.47 0.38 0.29 1.98 4 2 1.71 RS RS

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  • Structure, Morphology and Color Tone Properties of theNeodymium Substituted Hematite

    Tarequl Islam Bhuiyan, Nakanishi Makoto, Fujii Tatsuo, Takada Jun

    Memoirs of the Faculty of Engineering, Okayama University   41 ( 1 )   93 - 98   2007年1月

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    記述言語:英語   出版者・発行元:Faculty of Engineering, Okayama University  

    Co-precipitation method has been employed to fabricate neodymium substituted hematite with different compositions from the aqueous solution of their correspondingmetal salts. Thermal analysis and X-ray diffraction studies revealed the coexistence of Fe(2)O(3) and Nd(2)O(3) phases up to 1050℃ and formation of solid solution phase amongthem at 1100℃ and above temperatures, which was evidenced by shifting of the XRD peaks. Unit cell parameters and the cell volumes of the samples were found to increase by adding Nd(3+) ions in the reaction process. FESEM studies showed the suppression of particle growth due to the presence of Nd(3+) ions. Spectroscopic measurement evidenced that neodymium substituted hematite exhibited brighter yellowish red color tone than that of pure α-Fe(2)O(3).

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  • 錯体重合法による炭素/Fe-Ni-Cu合金複合材料の調製と構造、電波吸収特性の評価

    中西真, 内田有紀子, 藤井達生, 高田潤, 草野圭弘, 菊池丈幸

    炭素   No.228 ( 228 )   158 - 162   2007年

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    出版者・発行元:THE CARBON SOCIETY OF JAPAN  

    We have prepared Carbon/Fe-Ni-Cu ternary alloy composites by polymerized complex method. A single-phase Fe-Ni-Cu alloy could be obtained in carbon matrix by controlling pH of the citrate complex solution. It was revealed that the chemical compositions of metals in composites were maintained well by adding ethylene glycol into the complex solution. Crystallinity of both carbon matrix and Fe-Ni-Cu alloy particles were enhanced with increasing the carbonized temperature. The composite carbonized at 700°C had larger saturation magnetization and smaller coercivity than that carbonized at 500°C, which correlated with metal content and crystallite size of alloy. The composite carbonized at 700°C exhibited larger permeability and permittivity than carbon/Fe-Co alloy composites at frequency of GHz range.

    DOI: 10.7209/tanso.2007.158

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  • The valence state analysis of Ti in FeTiO<inf>3</inf> by soft X-ray spectroscopy

    Sei Fukushima, Takashi Kimura, Kenji Nishida, Vlaicu A. Mihai, Hideki Yoshikawa, Masahiro Kimura, Tatsuo Fujii, Hirofumi Oohashi, Yoshiaki Ito, Michiru Yamashita

    Microchimica Acta   155 ( 1-2 )   141 - 145   2006年9月

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    記述言語:英語   出版者・発行元:SPRINGER WIEN  

    The measurement of soft X-ray spectra, Ti Kα , Lα and O Kα, of Ti in several titanium oxide compounds was carried out by FE-WD-EPMA (wavelength dispersive - electron probe micro-analyzer with field emission type electron gun) and HRXRF (high-resolution X-ray fluorescence spectroscopy). From the results of measurements, it was found that the valence state of Ti in FeTiO (ilmenite) was at least partially Ti , might be the mixed state of Ti and Ti . And, Ti in MgTiO (ilmenite system) was confirmed as Ti . From the discussion, it can be presumed that the effective charge of the oxygen should be not-uniform and should be different subtlety by the cationic difference, Fe or Mg, even if it had equal crystal structure of the ilmenite system, and that this subtlety difference gave any effects on the valence state of Ti. 1,2 1,2 3 3 III IV III IV

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  • The effect of heat treatment temperature on the microstructure and magnetic properties of Ba<inf>2</inf>Co<inf>2</inf>Fe<inf>12</inf>O<inf>22</inf> (Co<inf>2</inf>Y) prepared by sol-gel method

    Nimai Chand Pramanik, Tatsuo Fujii, Makoto Nakanishi, Jun Takada, Sang II Seok

    Materials Letters   60 ( 21-22 )   2718 - 2722   2006年9月

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    記述言語:英語   出版者・発行元:ELSEVIER  

    Ferroxplana type hexagonal ferrite with composition Ba Co Fe O (Co Y) was prepared by polymeric sol-gel method from the aqueous solution of their corresponding metal salts. All the samples were characterized by using X-ray diffraction and scanning electron microscopic technique. The formation and the microstructure of the Ba Co Fe O was studied as a function of heat treatment temperature and it was observed that well defined hexagonal plate-like fine particles with particle sizes between 130 and 400 nm were formed at relatively lower temperature (900 °C) as compared to conventional solid state reaction method (1100 °C). Magnetic properties of the samples were also studied as a function of heat treatment temperature and it showed large saturation magnetization (M ) ranging from 30.9 to 47.6 emu/g and a wide range of coercivity (130∼1566 Oe) depending on the heat treatment temperature. The very high saturation magnetization at relatively lower temperature (say 800 °C) arises due to the presence of several high magnetic impurities, such as BaFe O and CoFe O . The saturation magnetization increases with increasing heat treatment temperature above 900 °C, while the coercivity showed a reversed order. © 2006 Elsevier B.V. All rights reserved. 2 2 12 22 2 2 2 12 22 s 12 19 2 4

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  • 28pXD-7 ナノ構造化炭素材料の水素貯蔵能を増強する鉄の分光法を用いた研究(28pXD 格子欠陥,ナノ構造(半導体・炭素),領域10(誘電体,格子欠陥,X線・粒子線,フォノン物性))

    宮岡 裕樹, 市川 貴之, 礒部 繁人, 藤井 達生, 藤井 博信

    日本物理学会講演概要集   61 ( 1 )   939 - 939   2006年3月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • FeTiO3/Fe2O3 Multilayered Films For New Magnetic Semiconductors Above Room Temperature

    Tatsuo Fujii, Yusuke Takada, Jun Takada

    Advances in Science and Technology   2006年

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  • Preparation and characterization of epitaxial Fe<inf>2-x</inf>Ti <inf>x</inf>O<inf>3</inf> solid solution films

    Tatsuo Fujii, Hideki Hashimoto, Yusuke Takada, Makoto Nakanishi, Jun Takada

    Ceramic Transactions   195   87 - 94   2006年

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    Thin films of hematite-ilmenite (α-Fe O -FeTiO ) solid solution series are proposed to be one of the new high-temperature magnetic semiconductors, We have successfully prepared well-crystallized epitaxial Fe Ti O films with various Ti content, x, between 0.6 and 1.0. The films were epitaxially formed on α-Al O (0001) single-crystalline substrates by reactive helicon plasma sputtering technique. The films prepared at lower substrate temperature below 700°C had the R3̄c structure, in which the Fe and Ti ions randomly occupied octahedral interstices. While the films prepared at higher substrate temperature above 700°C had the R3̄ structure, in which the octahedral interstices occupied by the Fe and Ti ions were arranged in an ordered way along the c-axis. Moreover the films prepared at the higher substrate temperature consisted of nearly stoichiometric oxygen concentration. However, with decreasing the substrate temperature the films seemed to have large cation vacancies and Fe ions were gradually oxidized to Fe . With decreasing the Ti content from x=1.0 to 0.6, the electric resistivity of the stoichiometric films was sharply decreased from 10 to 0.1 Ωcm because of the formation of mixed valence states between Fe and Fe . The stoichiometric films with x=0.6 were ferrimagnetic semiconductors at room temperature when the films had the R̄̄3 structure. 2 3 3 2-x x 3 2 3 2+ 3+ 2+ 3+

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  • Synthesis of Hexagonal Ferrites by Citric Complex Method

    Takeyuki Kikuchi, Tatsuya Nakamura, Masamichi Miki, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Yasunori Ikeda

    Advances in Science and Technology   2006年

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  • Synthesis of cARBON/Fe-Ni-Cu alloy composite by carbonization of organometallic polymers and their magnetic properties

    Yukiko Uchida, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Akinori Muto, Yusaku Sakata

    Ceramic Transactions   195   67 - 74   2006年

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    Carbon/Fe-Ni-Cu alloy composites were synthesized by carbonization of organometallic polymers obtained from ion exchanged chelate resins. The carbonization was performed at 900 °C in a N gas flow. The composition of the Fe-Ni-Cu alloy in a carbon matrix can be controlled by the adjusting solution compositions in the ion exchange process. The carbon obtained from the organometallic polymer was crystallized to a turbostratic structure. X-ray diffraction patterns revealed that the Cu, Fe and Ni elements in the ion exchanged chelate resins were crystallized to a Fe-Ni-Cu alloy after carbonization at 900°C. This result indicates that the formation of the ternary alloy in the carbon matrix is coincident with the crystallization of the well-ordered turbostratic structure of the carbon matrix. The alloy particles with an average size of about 200-700 nm were widely dispersed in the carbon matrix. The saturation magnetization and coercivity of the composites depended on the alloy composition. The saturation magnetization and coercivity of the carbon/Fe Ni Cu alloy composite were 7.9 emu/g and 167 Oe, respectively. 2 0.52 0.42 0.06

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  • Preparation of Z-type hexagonal ferrite, Co<inf>2</inf>Z, using alkaline mali de method

    Akira Sasaki, Makoto Nakanishi, Tatsuo Fujii, Jun Takada

    Ceramic Transactions   196   497 - 503   2006年

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    In this study, low temperature preparation conditions for Co Z (3BaO·2CoO·12Fe O ) particles were investigated by using alkaline halide method. The obtained particles were characterized by using X-ray diffraction and scanning electron microscopy techniques. Many factors such as the metal compositions, heating temperature, heating and cooling rates, and amount of flux reagents were changed for the preparation. The X-ray diffraction analysis indicated that (1) the metal compositions, (2) flux reagent, and (3) heating rate were important to obtain Co Z at low temperature using the alkaline halide method. Nearly monophasic Co Z was formed under the following conditions: metal compositional ratio of Ba : Co: Fe = 3.0 : 1.5 : 24 with 10wt% BaCl flux and rapid heating to 1200 °C for 6 hours. Co Z powders mixed with an EPDM rubber were pressed to a sheet form. The electromagnetic properties of rubber sheets were examined to apply to use as an electromagnetic wave absorber. 2 2 3 2 2 2 2

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  • Preparation and characterization of FeTiO<inf>3</inf>-Fe<inf>2</inf>O <inf>3</inf> solid solution system

    Miki Yamashita, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Hideki Yoshikawa, Yuuji Saitoh, Shin Ichi Fujimori, Keisuke Kobayashi

    Ceramic Transactions   196   505 - 512   2006年

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    The ilmenite-hematite solid-solution, xFeTiO -(1-x) α-Fe O samples with x=0.7-1.0. were prepared by standard solid state reaction technique in an evaculated quartz tube. The sample pellets were heated at 1200°C for 24 hr, then furnance cooled to room temperature . All samples consisted of a single phase of ilmenite structure. Lattice parameters of these samples estimated from the XRD patterns varied linearly with decreasing the Ti concentration on the basis of the Vegard's law. The saturating magnetization at 78 K was obtained at x=0.8 (Fe Ti O ), and the sample with x=0.7 (Fe Ti O ) was ferrimagnetic at room temperature. The carrier type measured by Seebeck coefficient was changed from p-type to n-type at about x=0.78 with decreasing the Ti concentration. Electronic states of Fe and Ti ions in FeTiO seemingly had the characteristic features of Fe and Ti respectively. However the Ti 2p→3p resonant valence band photoemission spectra of FeTiO had a clear density assigned to the Ti 3 d derived states. The small density appeared just below the Fermi edge was intrinsic for the FeTiO crystals because of identical x-ray absorption spectrum at Ti L edges between constant initial state and total electron yield mode. 3 2 3 1.2 0.8 3 1.3 0.7 3 3 3 3 2,3 1 2+ 4+

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  • Effects of pH control on preparation of Z-type hexagonal ferrite Ba <inf>3</inf>Co<inf>2</inf>Fe<inf>24</inf>O<inf>41</inf> by polymerized complex method

    Makoto Nakanishi, Asako Akiyama, Tatsuo Fujii, Jun Takada, Takeyuki Kikuchi, Yoshihiro Kusano

    Ceramic Transactions   196   435 - 440   2006年

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    The formation process of Z-type hexagonal ferrite, Ba Co Fe O , prepared by polymerized complex method and the effects of pH control of citrate complex solution were investigated. By heating a precursor, a pyrolyzed complex polymer, spinel phase, M-type ferrite and Y-type ferrite were formed sequently with increasing the heating temperature. By heating up to 1200°C, monophasic Z-type ferrite was not synthesized in usual preparation procedures. So pH of citrate complex solution was changed and the effects on formation process were examined. As ammonia solution was added to change the complex solution from acidic to basic, the phases in the pyrolysate changed form barium carbonate to barium nitrate and the crystallinity of the constituent phases decreased. By controlling pH to 11, monophasic Z-type ferrite was obtained by heating at 1200°C. On the other hand, pH control of the complex solution toward basic condition suppressed the formation of Y-type ferrite. It was revealed that the optimum conditions for preparing the complex solution depended on phases even for same Ba-Co-Fe-O system. 3 2 24 41

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  • Iodine intercalation and deintercalation of a Sr-free Bi-based cuprate: Bi<inf>2</inf>(La,Na)<inf>2</inf>CuO

    Yoshiaki Tanaka, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Yoshihiro Kusano, Yasunori Ikeda

    Ceramic Transactions   196   85 - 90   2006年

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    Iodine intercalation and deintercalation of a Sr-free Bi-based cuprate, Bi (La,Na) CuO:, have been investigated. It has been confirmed by powder X-ray diffraction and thermogravimetric analysis that the stage-1 iodine-intercalated compound Bi (La,Na) CuO l with x=1.0 was formed. As in the case of a Bi (Sr,La) CuO: (Bi-2201) specimen, expansion of the c-length of the stage-1 iodine-intercalated compound was 3.6 Å, compared with one half that of host compound. After deintercalation of the intercalated iodine, the stage-1 iodine-intercalated compound returned reversibly to the host compound. The powder X-ray diffraction pattern showed the formation of the intermediate phase containing a certain amount of iodine, not assigned to the stage-2 intercalated compound, during the deintercalation. Neither host compound nor iodine-intercalated compound exhibited superconductivity down to 2 K. 2 2 2 2 7 x 2 2

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  • Synthesis and characterization of cerium substituted hematite by sol-gel method

    Nimai Chand Pramanik, Tarequl Islam Bhuiyan, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Sang Il Seok

    Materials Letters   59 ( 28 )   3783 - 3787   2005年12月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Fine particles of cerium substituted hematite with different compositions were prepared by the sol-gel method from the aqueous solution of their corresponding metal salts. Mixed hydroxides of Fe and Ce were obtained by reacting aqueous NH with the aqueous solution of FeCl and Ce(NH ) (NO ) at pH 2.5-3.0) and they were heat treated at different temperatures between 400 and 1200°C in air for 2 h to get the mixed oxide product. Thermal analysis and X-ray diffraction studies revealed the coexistence of Fe O and CeO phase separately up to 900°C, and covalent interaction between them above 1000°C, which was evidenced by the shifting of the XRD peaks. Unit cell parameters and the cell volumes (V) of the samples derived between 1000 and 1200°C were found to be in the range a = 5.045-5.048 ± 0.007 Å, c = 13.774-13.815 ± 0.041 Å and V = 303.608-304.874 Å respectively. It was observed that both the lattice parameters and the cell volumes were higher than that of the pure α-Fe O (a = 5.036 Å, c = 13.749 Å, V = 301.976 Å ) system. The expansion of lattice parameters further supported the incorporation of the large Ce ion into the α-Fe O matrix. The lattice parameter increased with increasing Ce ion loading. FESEM studies showed the growth of the particles with increasing temperature though it was suppressed due to the presence of Ce ions as compared to the pure system. © 2005 Elsevier B.V. All rights reserved. 3+ 4+ 3 3 4+ 4+ 4+ 3 3 3 2 3 6 2 3 2 2 3 2 3

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  • Site-specific valence-band X-ray photoelectron spectra of a SrTiO <inf>3</inf> single-crystal by X-ray standing wave technique

    Tatsuo Fujii, Masahiro Kimura, Hideki Yoshikawa, Sei Fukushima

    Solid State Communications   136 ( 7 )   375 - 379   2005年11月

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    記述言語:英語   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Site-specific valence-band X-ray photoelectron spectra of SrTiO (111) were successfully obtained by using X-ray standing wave technique. Contributions of the Ti and SrO derived states to the valence-band spectra were clearly separated. The spectra provided not only site-specific but also bulk-sensitive information on the SrTiO crystal because of the use of a high-energy synchrotron X-ray source (hν=4750 eV) for photoelectron excitation with the large escape depth. The electronic structures calculated by the DV-Xα method using a (Sr Ti O ) cluster model well reproduced the observed structures in the valence-band spectra. The partial density of states of both Ti and Sr ions in SrTiO were mainly distributed over the bottom of the valence-band to produce the covalent bonding with O ions. © 2005 Elsevier Ltd. All rights reserved. 3 3 3 8 27 108 3 92-

    DOI: 10.1016/j.ssc.2005.09.013

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  • Magnetic properties of Fe<inf>1.2</inf>Ti<inf>0.8</inf>O <inf>3</inf>/Fe<inf>2</inf>O<inf>3</inf> bilayered films

    Tatsuo Fujii, Yusuke Takada, Makoto Nakanishi, Jun Takada

    IEEE Transactions on Magnetics   41 ( 10 )   2775 - 2777   2005年10月

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    記述言語:英語   出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

    Hematite-ilmenite (α-Fe O -FeTiO ) solid solution system is one of the candidates for high-temperature magnetic semiconductors. The intermediate composition, Fe Ti O , is known to have the maximum saturation magnetization at low temperature. We have successfully prepared well-crystallized Fe Ti O and Fe Ti Fe O bilayered films by using reactive helicon plasma sputtering. The Fe Ti O films without Fe O layers showed lower T of about 200 K, while the T of Fe Ti O layers in the bilayered films increased to about 220 K. The bilayered films had a sharp interface between Fe Ti O and α-Fe O . The strong magnetic coupling between two layers seemed to increase the T of the attached Fe Ti O layers. © 2005 IEEE. 2 3 3 1.2 0.8 3 1.2 0.8 3 1.2 0.8 2 3 1.2 0.8 3 2 3 C C 1.2 0.8 3 1.2 0.8 3 2 3 C 1.2 0.8 3

    DOI: 10.1109/TMAG.2005.854820

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  • The influence of the impurity element and the heat temperature upon the traditional Japanese red color pigment "bengara"

    Hiroshi Asaoka, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Yoshihiro Kusano, Ryu Murakami

    C e Ca   35 ( 2 )   85 - 91   2005年9月

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    The traditional Japanese red pigment called "bengara" has vivid yellowish red coloras compared with the pure hematite powder. The traditional "bengara" is composed of mainly hematite, for impurities, a small amount of quartz and corundum. The color of reproduced "bengara" was great influenced by the particles shape and size of hematite powder.

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  • 錯体重合法を応用した炭素/Fe-Co 合金複合材料の調製と磁気特性

    内田有紀子, 大石響子, 中西 真, 藤井達生, 髙田 潤, 草野圭弘, 菊池丈幸

    粉体および粉末冶金   52 ( 8 )   640 - 645   2005年8月

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    記述言語:日本語  

    DOI: 10.2497/jjspm.52.640

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  • Preparation and magnetic properties of the CoFe<inf>2</inf>O<inf>4</inf> thin films on Si substrate by sol-gel technique

    Nimai Chand Pramanik, Tatsuo Fujii, Makoto Nakanishi, Jun Takada

    Journal of Materials Science   40 ( 16 )   4169 - 4172   2005年8月

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    記述言語:英語   出版者・発行元:SPRINGER  

    A stable precursor for CoFe O thin film was prepared by sol-gel technique from the aqueous solution of FeCl •6H O and CoCl •6H O. Sol was deposited on a naturally oxidized silicon-substrate by spinning technique (2000 rpm) and heat treated at different temperatures ranging from 700 to 1100°C. Thickness of the films was controlled in the range of 400-500 nm and all the films were characterized by using XRD and SEM. The effects of temperature and the composition on the formation of CoFe O thin film were also studied. Films obtained at relatively lower temperature showed multi-phases of α-Fe O , CoFe O and CoO while the formation of CoFe O phase increases with increasing temperature. Furthermore, the composition of the solution in mol% has great role on the formation of CoFe O films and the film containing 50 mol% of Co exhibited CoFe O mono-phase. Surface morphology of the films was studied by scanning electron microscope (SEM). Magnetic properties of the films, studied by using vibrating sample magnetometer (VSM), showed relatively high saturation magnetization (8.04-22.21 kWb/m ) as well as high coercivity (44.59-63.30 kA/m). Saturation magnetization also increases with increasing heat treatment temperature. © 2005 Springer Science + Business Media, Inc. 2 4 3 2 2 2 2 4 2 3 2 4 2 4 2 4 2 4 2+ 2

    DOI: 10.1007/s10853-005-3819-1

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  • Development of nanograined hexagonal barium ferrite thin films by sol-gel technique

    Nimai Chand Pramanik, Tatsuo Fujii, Makoto Nakanishi, Jun Takada

    Materials Letters   59 ( 4 )   468 - 472   2005年2月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Nanograined hexagonal barium ferrite (BaFe O ) thin films have been developed on naturally oxidized Si substrates by sol-gel technique using aqueous solution of metal chlorides. Coated films were heat treated at different temperatures ranging from 450 to 900°C, and all the films were characterized by using X-ray diffraction (XRD), inductive coupled plasma (ICP) spectroscopy, and field emission scanning electron microscopy (FESEM). The effects of temperature on the formation of BaFe O thin film were studied, and it was observed that hexagonal barium ferrite thin films with grain sizes of about 50 nm were formed above 700°C. Study on the magnetic properties of the films by vibrating sample magnetometer (VSM) showed that films exhibited large saturation magnetization and high coercivity in the range 247-355 emu/cm and 2.70-4.22 kOe, respectively, while the Curie temperatures (□ ) were in the range 443-457°C. The effects of temperatures on the magnetic properties were also studied. © 2004 Elsevier B.V. All rights reserved. 12 19 12 19 c 3

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  • Oxidation resistance of Mo coated with Mo(Si,Al) <inf>2</inf> layer prepared by dipping into liquid of Al-25 mass%Si alloy

    Shinsuke Kunitsugu, Norihide Nishida, Takao Tomiya, Masahiro Nagae, Makoto Nakanishi, Tatsuo Fujii, Jun Takada

    Materials Transactions   46 ( 2 )   215 - 218   2005年2月

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    記述言語:英語   出版者・発行元:JAPAN INST METALS  

    A homogeneous layer of molybdenum alumininosilicide Mo(Si,Al) with C(40) structure was made on the sample surface of molybdenum by dip-coating technique using Al-25mass%Si liquid at 1123K. Adherent Al-Si was removed by soaking the dipped samples in the NaOH saturated hydraulic solution. The Mo samples coated with the Mo(Si,Al) layer were found to have excellent oxidation resistance in air even at 1473 K due to formation of a dense alumina film on the sample surface during oxidation. The formation of Mo (Si,Al) layer was also observed at the interface between the Mo substrate and the Mo(Si,Al) layer. ©2005 The Japan Institute of Metals. 2 2 5 3 2

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  • Development of Co<inf>1+x</inf>Fe<inf>2-x</inf>O<inf>4</inf> (x=0-0.5) thin films on SiO<inf>2</inf> glass by the sol-gel method and the study of the effect of composition on their magnetic properties

    Nimai Chand Pramanik, Tatsuo Fujii, Makoto Nakanishi, Jun Takada

    Materials Letters   59 ( 1 )   88 - 93   2005年1月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Spinel-type Co Fe O (x=0-0.5) thin films (∼450 nm thickness) on SiO glass substrate were prepared by the sol-gel method using spinning technique (2000 rpm) from the aqueous solution of FeCl .6H O and CoCl .6H O. All the films were heat treated at different temperatures ranging from 700 to 1100°C. The films were structurally characterized by using the X-ray diffraction technique (XRD), and the morphology was studied by field emission scanning electron microscope (FESEM). The effects of temperature and the composition ([Co ]/ [Fe ] ratio) on the formation of Co Fe O thin films were also studied. The films obtained at relatively low temperature showed mixed phases of α-Fe O , CoO, along with CoFe O , while the formation of the CoFe O phase increases with increasing temperature. Furthermore, the composition of the solution in terms of [Co ]/[Fe ] plays a great role on the formation and magnetic properties of the films. The magnetic properties of the films, studied using vibrating sample magnetometer (VSM), showed relatively small saturation magnetization, and coercivity was observed to be low as compared with that of other reports. Saturation magnetization also increases with increasing heat treatment temperature. © 2004 Elsevier B.V. All rights reserved. 1+x 2-x 4 2 3 2 2 2 1+x 2-x 4 2 3 2 4 2 4 2+ 3+ 2+ 3+

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  • Effect of Co2+ ion on the magnetic properties of sol-gel cobalt ferrite thin films

    Nimai Ch Pramanik, Tatsuo Fujii, Makoto Nakanishi, Jun Takada

    Journal of Materials Chemistry   14 ( 22 )   3328 - 3332   2004年11月

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    記述言語:英語   出版者・発行元:ROYAL SOC CHEMISTRY  

    The effect of Co ion on the magnetic properties of the sol-gel derived cobalt ferrite thin films (400 nm thickness) was studied. Films with different solution composition ([Co ]/[Fe ] = 0.5-1.0) were deposited on a Si substrate from the precursor containing an aqueous solution of FeCl ·6H O and CoCl · 6H O. Deposited films were heat treated at different temperatures (700-1100 °C) and were characterized by X-ray diffraction using Cu Kα radiation. The films containing a nonstoichiometric α-(Fe Co ) O phase were obtained in addition to a small amount of CoO at relatively lower temperatures. With increasing heat treatment temperature, nonstoichiometric α-(Fe Co ) O was decomposed to stoichiometric α-Fe O and the CoFe O phase was intensified. Only the films obtained from the solution enriched with Co showed the single phase of CoFe O , though the Co to Fe content ratio analyzed by inductive coupled plasma spectroscopy (ICP) and energy dispersive X-ray spectroscopy (EDX) was nearly consistent with that of the starting solutions. The study of surface morphology of the films by using field emission scanning electron microscope (FESEM) showed that films were homogeneously distributed throughout the surface of the substrate and the grain sizes were in the range of 60 to 140 nm. Magnetic properties of the films, including the Curie temperature, were studied by using a vibrating sample magnetometer (VSM) and conversion electron Mössbauer spectroscopy (CEMS). The Curie temperature and the magnetic hyperfine fields of the films slightly decreased with increasing molar ratio of the Co and Fe ions while the saturation magnetization reached a maximum value with the film composition of x = 0.28. 2+ 2+ 3+ 2+ 3+ 3 2 2 2 1-x x 2 3 1-x x 2 3 2 3 2 4 2 4

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  • Microstructure and formation process of the characteristic reddish color pattern Hidasuki on Bizen stoneware: Reactions involving rice straw

    Yoshihiro Kusano, Minoru Fukuhara, Tatsuo Fujii, Jun Takada, Ryu Murakami, Akira Doi, Laurence Anthony, Yasunori Ikeda, Mikio Takano

    Chemistry of Materials   16 ( 19 )   3641 - 3646   2004年9月

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    記述言語:英語   出版者・発行元:AMER CHEMICAL SOC  

    The formation process of Hidasuki, a characteristic reddish coloring pattern on traditional Japanese unglazed stoneware called Bizen, was studied through model experiments. Pellets of the same type of clay used to form Bizen stoneware were heated to 1250 °C with and without contact with rice straw and then were cooled at different rates. A reddish color appeared for relatively slowly cooled samples when rice straw was present. Owing to the presence of potassium in the rice straw, the mullite (3(Al,Fe) O ·2SiO ) the major phase formed in the absence of rice straw, was replaced by corundum (α-Al O ), hematite (α-Fe O ), and others in the surface region of about 50 μm in depth. The corundum precipitated as hexagonal platelike crystals, and on the edges of these crystals the hematite grew epitaxially. The growth continued so that the primary corundum crystals were wholly covered by hematite to form a specific single crystalline α-Fe O /α-Al O /α-Fe O structure. The contribution of this unique microstructure to coloring is discussed. On the basis of these analytical results, the Hidasuki pattern was reproduced artificially in the form of written characters. 2 3 2 2 3 2 3 2 3 2 3 2 3

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  • クエン酸法により合成したLa-Co置換M型Srフェライト微粒子の磁気特性

    菊池 丈幸, 中村 龍哉, 中西 真, 藤井 達生, 高田 潤, 池田 靖訓, 三木 雅道

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan   28   419 - 419   2004年9月

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  • Ilmenite-hematite solid solution films for novel electronic devices

    Tatsuo Fujii, Masakazu Kayano, Yusuke Takada, Makoto Nakanishi, Jun Takada

    Solid State Ionics   172 ( 1-4 SPEC. ISS. )   289 - 292   2004年8月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Unique magnetic and electric properties of solid solutions of ilmenite (FeTiO ) and hematite (α-Fe O ) can be expected for new electronics, optics and spintronics applications. We have successfully prepared well-crystallized and epitaxial Fe Ti O (001) films on α-Al O (001) substrates by reactive helicon plasma-sputtering technique. Structure, magnetic and electric properties of the films were seriously dependent on both the oxygen pressure and the substrate temperature during the sputtering deposition. The subsequent annealing of the films in vacuum at high temperature (600 °C) promoted the order (R3̄) structure of Fe Ti O , where the Ti and Fe ions occupied the cation sites alternatively along the c-axis. Only the films having the R3̄ symmetry had large ferrimagnetic moments at low temperature (78 K), although the magnetization values were depending on not only the order parameter between the R3̄ and the R3̄c structures but also the oxidization states of Fe ions in Fe Ti O . The film prepared at an oxygen partial pressure ratio of 1.4% and substrate temperature of 400 °C had considerably large spontaneous magnetization of 275 emu/cm at 78 K after the subsequent annealing at 600 °C. However, highly oxidized nonstoichiometirc Fe Ti O films with the R3̄c symmetry could not give the ordered structure with the R3̄ symmetry. © 2004 Elsevier B.V. All rights reserved. 3 2 3 1.23 0.77 3+δ 2 3 1.23 0.77 3+δ 1.23 0.77 3+δ 1.23 0.77 3+δ 3

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  • Preparation of Y-type Hexagonal Ferrite’s Films by Polymerized Complex Method

    Koutarou Komatsu, Makoto Nakanishi, Tatsuo Fujii, Jun Takada

    Journal of Magnetism and Magnetic Materials   272-276 ( SUPPL. 1 )   E1831 - E1832   2004年5月

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  • Preparation and Characterization of Epitaxial Fe2-xTixO3+δ Films

    Tatsuo Fujii, Masakazu Kayano, Yusuke Takada, Makoto Nakanishi, Jun Takada

    Journal of Magnetism and Magnetic Materials   272-276 ( III )   2010 - 2011   2004年5月

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  • 27pXN-12 Ti Kβ X線輻射スペクトルにおける化学結合効果(原子・分子)(領域1)

    栃尾 達紀, 大橋 浩史, 伊藤 嘉昭, Mihai Vlaicu A., 福島 整, 藤井 達生, 山下 満

    日本物理学会講演概要集   59 ( 1 )   158 - 158   2004年3月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • X 線定在波法によるSrTiO3 結晶のサイト選択的XPS 測定

    藤井達生, 木村昌弘, 吉川英樹, 福島 整

    Journal of Surface Analysis   11 ( 3 )   165 - 169   2004年

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    記述言語:日本語   出版者・発行元:表面分析研究会  

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  • 新規広帯域高周波帯電磁波吸収体の研究開発

    高田 潤, 中西 真, 藤井達生

    機械の研究vol.56, no.5, pp.536-542   vol.56, no.5, pp.536-542 ( 5 )   536 - 542   2004年

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    記述言語:日本語   出版者・発行元:養賢堂  

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  • Crystalline Control of Bincho Charcoal by using Catalytic Graphitization and Electromagnetic Wave Absorption Characteristics of Derived Carbon

    Yukiko Uchida, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Akinori Muto, Yusaku Sakata, Yoshihiro Kusano, Takeyuki Kikuchi

    Transactions of the Materials Research Society of Japan   2004年

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  • 814 吹屋ベンガラのキャラクタリゼーションとその再現(表面改質・色彩評価,一般セッション,第53期学術講演会)

    浅岡 裕史, 中西 真, 藤井 達生, 高田 潤

    学術講演会講演論文集   53   228 - 228   2004年

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    記述言語:日本語   出版者・発行元:日本材料学会  

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  • 807 高周波用Y型六方晶フェライト薄膜の作製と磁気特性(薄膜物性,一般セッション,第53期学術講演会)

    小松 幸太郎, 中西 真, 藤井 達生, 高田 潤

    学術講演会講演論文集   53   215 - 215   2004年

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  • 810 フェライト/SiC複合焼結体の作製と電磁波吸収特性(セラミックスの物性評価,一般セッション,第53期学術講演会)

    中西 真, 小倉 和生, 藤井 達生, 高田 潤

    学術講演会講演論文集   53   220 - 221   2004年

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  • 吹屋ベンガラのキャラクタリゼーションとFe2O3-Al2O3系赤色顔料の合成

    朝岡裕史, 草野圭弘, 中西 真, 藤井達生, 高田 潤

    粉体および粉末冶金   50 ( 12 )   1062 - 1067   2003年12月

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    記述言語:日本語  

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  • 22aPS-73 光電子分光法による鉄-チタン酸化物の電子状態

    藤井 達生, 栢野 真和, 高田 裕輔, 中西 真, 高田 潤, 伊藤 嘉昭, 木村 昌弘, Vlaicu M. A., 吉川 英樹, 福島 整, 田中 彰博

    日本物理学会講演概要集   58 ( 2 )   528 - 528   2003年8月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • 31pXF-6 エピタキシャル FeTiO_3 薄膜の電子状態

    藤井 達生, 栢野 真和, 高田 裕輔, 中西 真, 高田 潤, 大橋 浩史, 重岡 伸之, 伊藤 嘉昭, 木村 昌弘, Vlaicu M. A., 吉川 英樹, 福島 整, 田中 彰博, 山下 満

    日本物理学会講演概要集   58 ( 1 )   475 - 475   2003年3月

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  • Microstructure and formation mechanism of fire-make pattern on Japanese traditional “BIZEN” earthenware

    Y. Kusano, A. Doi, M. Nakanishi, T. Fujii, J. Takada, M. Fukuhara, R. Murakami

    Proceedings of 10th International Ceramics Congress, Science for New Technology of Silicate Ceramics   2003年

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  • The influence of the additional element and the heat temperature upon traditional red color pigment

    H. Asaoka, M. Nakanishi, T. Fujii, J. Takada, Y. Kusano, R. Murakami

    Proceedings of 10th International Ceramics Congress, Science for New Technology of Silicate Ceramics   2003年

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  • FeTiO3中のTiの化学状態

    福島整, 藤井達生, 高田裕輔, 伊藤嘉昭, 大橋浩史, 吉川英樹, 田中彰博, 山下満, 元山宗之

    応用物理学関係連合講演会講演予稿集   50th ( 2 )   2003年

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  • プレセラミックス法によるフェライト系複合材料の作製と電波吸収特性

    高田潤, 中西真, 藤井達生

    日本応用磁気学会誌   26   818 - 822   2002年

  • Nonstoichiometry of epitaxial FeTiO<inf>3+δ</inf> films

    Tatsuo Fujii, Makoto Sadai, Masakazu Kayano, Makoto Nakanishi, Jun Takada

    Materials Research Society Symposium - Proceedings   746   55 - 60   2002年

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    Epitaxial thin films of (001)-oriented FeTiO were prepared on α-Al O (001) single crystalline substrates by helicon plasma sputtering technique. The FeTiO films had large oxygen nonstoichiometry, which seriously depended on both substrate temperature and oxygen pressure during the sputtering deposition. The valence states of Fe ions in FeTiO changed monotonically from Fe to Fe with decreasing the substrate temperature from 900 to 400°C or with increasing the oxygen pressure from 0.9 to 1.8×10 Pa. The change of Fe valence states from Fe to Fe induced the magnetic phase transition only for the films prepared at 900°C. The films containing Fe were paramagnetic while those with Fe were antiferromagnetic at room temperature. The oxygen nonstoichiometry of the FeTiO films was probably produced by cation vacancies and disarrangement of Fe and Ti ions, which randomly occupied both interstitial and substitutional sites of the FeTiO related structure. 3+δ 2 3 3+δ 3+δ 3+δ 3 2+ 3+ -6 2+ 3+ 2+ 3+ 3+ 4+

    DOI: 10.1557/proc-746-q6.10

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  • Low-temperature growth of c-axis-oriented Y-type hexagonal ferrite thin films by the polymeric precursor method

    Tatsuo Fujii, Aiko Harano, Makoto Nakanishi, Jun Takada

    Journal of Materials Research   16 ( 9 )   2471 - 2474   2001年9月

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    記述言語:英語   出版者・発行元:MATERIALS RESEARCH SOCIETY  

    Well-crystallized Ba Zn Fe O (Zn -Y) films with high c-axis oritentation were successfully formed on Ag substrates at low temperature by the polymeric precursor method. A precursor solution with stoichiometric Ba , Zn , and Fe ions was deposited on the substrates by a dip-coating. The films were then heat-treated at temperatures ranging from 700 to 900°C. The crystallization process of c-axis-oriented Zn -Y films occurred at the considerably low temperature of 750°C, though a small amount of spinel oxides contaminated them. The films had hexagonal grain structures which were developed by increasing the heat-treatment temperature. Magnetization curves of the Zn -Y film heated at 900°C clearly indicated that the film had large in-plane magnetic anisotropy and had small in-plane coercivity. 2 2 12 22 2 2 2 2+ 2+ 3+

    DOI: 10.1557/JMR.2001.0338

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  • NO2-assisted molecular-beam epitaxy of wustitelike and magnetitelike Fe oxynitride films on MgO(100)

    FC Voogt, PJM Smulders, GH Wijnja, L Niesen, T Fujii, MA James, T Hibma

    PHYSICAL REVIEW B   63 ( 12 )   2001年3月

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    記述言語:英語   出版者・発行元:AMER PHYSICAL SOC  

    In an attempt to obtain wustite Fe1-xO as epitaxial films on MgO(100), NO2-assisted molecular-beam epitaxy was applied. At low NO2 fluxes, the low-energy electron diffraction and reflection high-energy electron diffraction images indeed indicate the formation of a rocksaltlike structure. In addition, Mossbauer spectroscopy provides evidence for the formation of a phase that is paramagnetic at room temperature. However, the layers are not pure oxides but are well-ordered oxynitrides with composition Fe1-xO1-yNy. The nitrogen atoms occupy substitutional sites on the oxygen-anion sublattice. Similarly, at slightly higher NO2 fluxes, magnetitelike oxynitride films with composition Fe3+deltaO4-yNy are obtained. By correlating x-ray photoelectron spectroscopy spectra with the intensity oscillation periods observed during reflection high-energy electron diffraction, it is possible to derive the complete stoichiometry of the films. We propose that the abrupt incorporation of nitrogen atoms only occurs if the atomic oxygen provided by the NO2 flux is insufficient to form a stoichiometric Fe3O4.

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  • Exchange coupling and spin-flip transition of CoFe<inf>2</inf>O<inf>4</inf>/α-Fe<inf>2</inf>O<inf>3</inf> bilayered films

    Tatsuo Fujii, Takuya Yano, Makoto Nakanishi, Jun Takada

    Materials Research Society Symposium - Proceedings   674   2001年

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    CoFe O /α-Fe O (ferrimagnetic/antiferromagnetic) bilayered films were prepared on α-Al O (102) single-crystalline substrates by helicon plasma sputtering. A well-crystallized epitaxial α-Fe O (102) layer was formed on the substrate, while CoFe O grown on α-Fe O (102) was a polycrystalline layer with a (100)-preferred orientation. The α-Fe O (102) films without CoFe O layers clearly showed a spin-flip transition at about 400 K. The spins aligned perpendicular to the film plane at room temperature changed their direction within the film plane above 400 K. However the α-Fe O base layers of CoFe O /α-Fe O bilayered films did not show any spin-flip transition. The CoFe O layer on α-Fe O had a large in-plane magnetic anisotropy, while the spin axis of the α-Fe O (102) base layer was directed perpendicular to the film plane. The magnetization of ferrimagnetic CoFe O layers was coupled perpendicularly to the spin axis of antiferromagnetic α-Fe O layers due to the exchange coupling at the interface between CoFe O and α-Fe O . 2 4 2 3 2 3 2 3 2 4 2 3 2 3 2 4 2 3 2 4 2 3 2 4 2 3 2 3 2 4 2 3 2 4 2 3

    DOI: 10.1557/proc-674-t1.10

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  • Synthesis and properties of Pb-doped Bi-2212 phase

    Y. Kusano, A. Doi, M. Nakanishi, T. Fujii, J. Takada, Y. Ikeda, M. Takano

    Key Engineering Materials   206-213 ( II )   1469 - 1472   2001年

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    記述言語:英語   出版者・発行元:TRANS TECH PUBLICATIONS LTD  

    Effects of Pb-substitution on the electrical and magnetic properties and the microstructure of the Bi-based cuprate superconductors, especially Bi-2212 (Bi Sr CaCu O ) polycrystalline phase, have been studied by XRD, SEM, TEM and magnetic measurements. The larger hysteresis loops of the Pb-substituted Bi-2212 phase in M-H curves were observed in comparison with the Pb-free Bi-2212 phase. The disorder of the structural modulation and the formation of micro-twins were found in the Pb-doped Bi-2212 phase by TEM observations. These results were caused by inhomogeneity of Pb concentration in the crystal. 2 2 2 8+δ

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  • Low-temperature growth of C-axis oriented Y-type hexagonal ferrite's films by polymerized complex method

    Tatsuo Fujii, Koutarou Komatsu, Makoto Nakanishi, Jun Takada

    Materials Research Society Symposium Proceedings   656   43 - 48   2001年

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    Well-crystallized Y-type hexagonal ferrite (Me -Y, Me=Zn and Co) films with highly c-axis orientation were successfully prepared on Ag substrates by dip coating technique. The procedure consisted of preparation of homogeneous metal-organic solution by polymerized complex method, dip coating and subsequent heat-treatment. The films deposited on α-Al O easily reacted with the substrate, while the films deposited on Ag formed hexagonal planar structures. The formation temperature of Me -Y structures on Ag was 800 °C, which was much lower than that of Me -Y bulk crystals. The Me -Y films on Ag had a large in-plane magnetic anisotropy. The observed anisotropy field of the Zn -Y film was about 13 kOe and that of Co -Y was too large beyond our experimental limits. © 2001 Materials Research Society. 2 2 3 2 2 2 2 2

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  • Characteristics of microwave absorption of Ni-Zn-ferrite/SiC hemi-crystallized composites

    Makoto Nakanishi, Tomonori Shibuya, Tatsuo Fujii, Jun Takada

    Materials Research Society Symposium Proceedings   656   37 - 42   2001年

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    In order to develop wide-band microwave absorbers we tried to prepare composite absorbers between the magnetic loss (Ni-Zn-ferrite) and the dielectric loss (SiC) materials. The dry or wet mixtures of Ni-Zn-ferrite and polycarbosilane (PCS) were cured in air and were then subjected to pyrolysis forming of the ferrite composites. The composites produced by the wet mixing had granular structure: the PCS surrounding the ferrite particles suppressed the sintering and the grain growth of the ferrite composites during pyrolysis. The matching frequency due to the magnetic loss linearly increased with increasing the PCS content. Moreover the ferrite/SiC hemi-crystallized composite cured at 473 K for 24 hours showed wide-band absorption spectrum having the both magnetic and dielectric losses. © 2001 Materials Research Society.

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  • Anomalous field-induced magnetic transitions in V<inf>5</inf>X<inf>8</inf> (X = S,Se)

    M. Nakanishi, K. Yoshimura, K. Kosuge, T. Goto, T. Fujii, J. Takada

    Journal of Magnetism and Magnetic Materials   221 ( 3 )   301 - 306   2000年11月

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    記述言語:英語   出版者・発行元:Elsevier Science Publishers B.V.  

    The magnetization of V S and V Se was measured in pulsed high magnetic fields up to 39 T. The anomalies were observed in the magnetization curves for both V S and V Se . For V S , the anomaly at lower field is thought to correspond to spin flopping. The magnetization curves exhibited saturation for both compounds and the values of the ordered moments for V S and V Se were estimated to be 1.5 and 1.2 μ /V from the saturation moments, respectively. Our results support the magnetic structure of V S proposed by neutron diffraction measurements. 5 8 5 8 5 8 5 8 5 8 5 8 5 8 B 5 8 I

    DOI: 10.1016/S0304-8853(00)00509-6

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  • プレセラミックス法によるNi-Znフェライト/SiC系複合焼結体の作製と電磁波吸収特性

    粉体および粉末冶金   47 ( 8 )   927 - 930   2000年8月

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    記述言語:日本語  

    DOI: 10.2497/jjspm.47.927

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  • 重イオン照射によるBi系超伝導体へのピニングセンターの導入

    高田潤, 菊池丈幸, 中西真, 藤井達生, 長江正寛, 草野圭弘, 池田靖訓, 安田仲宏, 村上健

    NIRS-M (Natl Inst Radiol Sci)   ( 139 )   203 - 204   2000年4月

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  • Anomalous field-induced magnetic transitions in V5X8 (X = S,Se)

    M. Nakanishi, K. Yoshimura, K. Kosuge, T. Goto, T. Fujii, J. Takada

    Journal of Magnetism and Magnetic Materials   221 ( 3 )   301 - 306   2000年

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    記述言語:英語   出版者・発行元:Elsevier Science Publishers B.V.  

    The magnetization of V5S8 and V5Se8 was measured in pulsed high magnetic fields up to 39 T. The anomalies were observed in the magnetization curves for both V5S8 and V5Se8. For V5S8, the anomaly at lower field is thought to correspond to spin flopping. The magnetization curves exhibited saturation for both compounds and the values of the ordered moments for V5S8 and V5Se8 were estimated to be 1.5 and 1.2 μB/VI from the saturation moments, respectively. Our results support the magnetic structure of V5S8 proposed by neutron diffraction measurements.

    DOI: 10.1016/S0304-8853(00)00509-6

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  • Electric and Magnetic Properties of epitaxial Fe2-XTiXO3+δ films

    Mat. Res. Soc. Symp. Proc.,   623   191 - 196   2000年

  • ヘリコンスパッタ法によるCoFe_2O_4/α-Fe_2O_3二層膜の作製

    矢野 拓哉, 藤井 達生, 中西 真, 高田 潤

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan   23   20 - 20   1999年10月

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  • 固相法により作製したLi添加Bi-2212相への電気化学的手法によるLiインターカレーション

    粉体および粉末冶金   46 ( 9 )   990 - 993   1999年9月

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    記述言語:日本語  

    DOI: 10.2497/jjspm.46.990

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  • 反応性蒸着法によるFeTiO3-α-Fe2O3固溶体薄膜の作成

    粉体および粉末冶金   46 ( 6 )   643 - 647   1999年6月

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    記述言語:日本語  

    DOI: 10.2497/jjspm.46.643

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  • In situ xps analysis of various iron oxide films grown by (formula presented)-assisted molecular-beam epitaxy

    T. Fujii, F. M.F. de Groot, G. A. Sawatzky, F. C. Voogt, T. Hibma, K. Okada

    Physical Review B - Condensed Matter and Materials Physics   59 ( 4 )   3195 - 3202   1999年

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    記述言語:英語  

    We report on a systematic analysis of x-ray photoelectron spectroscopy (XPS) core- and valence-level spectra of clean and well-characterized iron oxide films, i.e., (Formula presented) (Formula presented) (Formula presented) and (Formula presented) All iron oxide films were prepared epitaxially by (Formula presented)-assisted molecular-beam epitaxy on single crystalline MgO(100) and (Formula presented) substrates. The phase and stoichiometry of the films were controlled precisely by adjusting the (Formula presented) pressure during growth. The XPS spectrum of each oxide clearly showed satellite structures. These satellite structures were simulated using a cluster-model calculation, which could well reproduce the observed structures by considering the systematic changes in both the Fe (Formula presented) to O (Formula presented) hybridization and the (Formula presented) electron-correlation energy. The small difference in the satellite structures between (Formula presented) and (Formula presented) resulted mainly from changes in the Fe-O hybridization parameters, suggesting an increased covalency in (Formula presented) compared to (Formula presented) With increasing reduction in the (Formula presented) system, the satellite structures in XPS became unresolved. This was not only due to the formation of (Formula presented) ions, but also to nonhomogeneous changes in the hybridization parameters between octahedral and tetrahedral (Formula presented) ions. © 1999 The American Physical Society.

    DOI: 10.1103/PhysRevB.59.3195

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  • In situ xps analysis of various iron oxide films grown by (formula presented)-assisted molecular-beam epitaxy

    T. Fujii, F. M.F. de Groot, G. A. Sawatzky, F. C. Voogt, T. Hibma, K. Okada

    Physical Review B - Condensed Matter and Materials Physics   59 ( 4 )   3195 - 3202   1999年

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    記述言語:英語  

    We report on a systematic analysis of x-ray photoelectron spectroscopy (XPS) core- and valence-level spectra of clean and well-characterized iron oxide films, i.e., (Formula presented) (Formula presented) (Formula presented) and (Formula presented) All iron oxide films were prepared epitaxially by (Formula presented)-assisted molecular-beam epitaxy on single crystalline MgO(100) and (Formula presented) substrates. The phase and stoichiometry of the films were controlled precisely by adjusting the (Formula presented) pressure during growth. The XPS spectrum of each oxide clearly showed satellite structures. These satellite structures were simulated using a cluster-model calculation, which could well reproduce the observed structures by considering the systematic changes in both the Fe (Formula presented) to O (Formula presented) hybridization and the (Formula presented) electron-correlation energy. The small difference in the satellite structures between (Formula presented) and (Formula presented) resulted mainly from changes in the Fe-O hybridization parameters, suggesting an increased covalency in (Formula presented) compared to (Formula presented) With increasing reduction in the (Formula presented) system, the satellite structures in XPS became unresolved. This was not only due to the formation of (Formula presented) ions, but also to nonhomogeneous changes in the hybridization parameters between octahedral and tetrahedral (Formula presented) ions. © 1999 The American Physical Society.

    DOI: 10.1103/PhysRevB.59.3195

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  • NO2-assisted molecular-beam epitaxy of Fe3O4,Fe3-δO4,and γFe2O3 thin films on MgO(100)

    Physical Review B,   60 ( 15 )   11193 - 11206   1999年

  • 25a-PS-116 V_XNbS_<2-δ>の構造と磁性

    松野 幸泰, 中西 真, 藤井 達生, 高田 潤

    日本物理学会講演概要集   53 ( 2 )   475 - 475   1998年9月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • LiドープBi2212相に関する分光学的研究

    高田潤, 中西真, 菊池丈幸, 藤井達生, 長田実, 垣花真人

    東京工業大学応用セラミックス研究所共同利用研究報告書   1997   74   1998年9月

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  • Fe3O4/MO(M=Ni,Co)人工格子の作製と磁性

    粉体および粉末冶金   45 ( 1 )   58 - 62   1998年1月

  • 反応性蒸着法によるFeTiO_3-α-Fe_2O_3固溶体薄膜の作製

    藤井 達生, 阿山 兼士, 中西 真, 高田 潤

    日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan   21   457 - 457   1997年10月

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  • Li doping into the Pb substituted Bi-2212 phase by electrochemical method

    Hirofumi Joko, Masashi Fujiwara, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Yoshihiro Kusano, Yasuo Takeda, Yasunori Ikeda, Mikio Takano, Yoshichika Bando

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   44 ( 8 )   792 - 796   1997年8月

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    Effects of electrochemical Li-doping to the Pb-substituted Bi-2212 phase on its structural and superconducting properties were studied. Bi Pb Sr Ca Cu O was lithiated through an electrochemical method at constant applied potential at room temperature. In the electrochemically Li-doping samples, the original crystal symmetry, tetragonal structure, was maintained and any secondary phase was not formed. The amount of doped Li for Bi Pb Sr Ca Cu O was much lager than that for Bi Sr Ca Cu O at the same reaction periods. Analysed maximum Li content y for Li Bi Pb Sr Ca Cu O was found to be 0.53, which was remarkably high in comparison with y=0.37 for Li Bi Sr Ca Cu O . The lattice parameters (a,c) of Li Bi Pb Sr Ca Cu O increased continuously in a similar trend to that of Li Bi Sr Ca Cu O . Tc remains almost constant around 85K as the Li content y increased. 1.8 0.2 1.5 1.5 2 z 1.8 0.2 1.5 1.5 2 z 2 1.5 1.5 2 z y 1.8 0.2 1.5 1.5 2 z y 2 1.5 1.5 2 z y 1.8 0.2 1.5 1.5 2 z y 2 1.5 1.5 2 z

    DOI: 10.2497/jjspm.44.792

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  • Electrochemical lithium intercalation into the Bi-2212 phase

    M. Fujiwara, M. Nakanishi, Y. Kusano, T. Fujii, J. Takada, Y. Takeda, Y. Ikeda

    Physica C: Superconductivity and its Applications   279 ( 3-4 )   219 - 224   1997年6月

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    記述言語:英語   出版者・発行元:Elsevier  

    Effects of lithium intercalation into the Bi-2212 phase on its structural and superconducting properties were studied using monophasic samples of Bi Sr Ca Cu O lithiated through an electrochemical method at a constant applied voltage at room temperature. The amount of doped lithium was found by ICP analysis to be in the range of 0 ≤ y ≤ 0.37 for Li Bi Sr Ca Cu O depending upon experimental conditions. However, the oxygen content determined by coulometric titration remained almost unchanged after the lithiation. The electrochemical lithium intercalation led to a very interesting change in T , though the original tetragonal structure and oxygen content remained essentially the same: T first increased rapidly as y increased, reached a maximum of 94 K, and then decreased to zero. The drastic T change is ascribed to a decrease in the hole concentration. Thus, the electrochemical lithium-doping provides us with a great advantage of easily controlling T at room temperature by changing electrochemical conditions while keeping the original crystal symmetry. © 1997 Elsevier Science B.V. 2 1.5 1.5 2 z y 2 1.5 1.5 2 z c c c c

    DOI: 10.1016/S0921-4534(97)00177-9

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  • Electrochemical lithium intercalation into the Bi-2212 phase

    M. Fujiwara, M. Nakanishi, Y. Kusano, T. Fujii, J. Takada, Y. Takeda, Y. Ikeda

    Physica C: Superconductivity and its Applications   279 ( 3-4 )   219 - 224   1997年6月

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    記述言語:英語   出版者・発行元:Elsevier  

    Effects of lithium intercalation into the Bi-2212 phase on its structural and superconducting properties were studied using monophasic samples of Bi2Sr1.5Ca1.5Cu2Oz lithiated through an electrochemical method at a constant applied voltage at room temperature. The amount of doped lithium was found by ICP analysis to be in the range of 0 ≤ y ≤ 0.37 for LiyBi2Sr1.5Ca1.5Cu2O z depending upon experimental conditions. However, the oxygen content determined by coulometric titration remained almost unchanged after the lithiation. The electrochemical lithium intercalation led to a very interesting change in Tc, though the original tetragonal structure and oxygen content remained essentially the same: Tc first increased rapidly as y increased, reached a maximum of 94 K, and then decreased to zero. The drastic Tc change is ascribed to a decrease in the hole concentration. Thus, the electrochemical lithium-doping provides us with a great advantage of easily controlling Tc at room temperature by changing electrochemical conditions while keeping the original crystal symmetry. © 1997 Elsevier Science B.V.

    DOI: 10.1016/S0921-4534(97)00177-9

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  • 28a-PS-82 バナジウムカルコゲナイドの磁気転移II

    中西 真, 藤井 達生, 高田 潤, 吉村 一良, 小菅 皓二, 後藤 恒昭

    日本物理学会講演概要集   52 ( 1 )   424 - 424   1997年3月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • Growth and properties of multilayered Ba- and Sr-Ferrites' films

    T. Fujii, H. Kato, Y. Miura, J. Takada

    Journal De Physique. IV : JP   7 ( 1 )   C1-485-486   1997年3月

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    Thin films of c-axis oriented Ba- and Sr-hexaferrits (BaM and SrM) were prepared by reactive evaporation method without any post heat treatments. Subsequently growth of BaM/SrM multilayered films was tried and the sidebands in XRD clearly appeared. According to magnetization measurements all films had the perpendicular magnetic anisotropy. However the M for BaM film was only 55% of that for the bulk. A broad background in Mössbauer spectrum for the BaM suggested the fluctuating magnetic moments. Though the M for SrM film was improved it had some inplane magnetization components. To combine the advantages of BaM and SrM individual films, the BaM/SrM multilayered film exhibited good magnetic properties: The M was recovered to about 80% of the bulk value and the inplane magnetization components disappeared in both the magnetization curves and the Mössbauer spectrum. s s s

    DOI: 10.1051/jp4:19971197

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  • Magnetite Fe<inf>3-δ</inf>O<inf>4</inf>: A stoichiometry and structure analysis of MBE grown thin films using NO<inf>2</inf> as the oxidizing source

    F. C. Voogt, T. Hibma, P. J.M. Smulders, L. Niesen, T. Fujii, P. A.A. van der Heijden, R. J.M. van de Veerdonk, P. J. van der Zaag

    Journal De Physique. IV : JP   7 ( 1 )   601 - 602   1997年3月

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    Epitaxial single crystalline films of iron oxides have been grown on MgO(100) substrates by means of MBE. Natural Fe or Fe was evaporated from alumina crucibles, and oxidized simultaneously with a dosed flux of NO . The resulting oxide layers have been characterized in situ with RHEED, LEED, XPS, and AES. RHEED intensity oscillations, observed during deposition of the oxides, indicate a layer-by-layer growth for all substrate temperatures between 373 and 673 K. A stoichiometry analysis with CEMS, performed ex situ, shows that it is straightforward to prepare both the stable magnetite Fe O and the metastable maghemite γ-Fe O phases. Moreover, also all solid solutions in between these two extreme phases, i.e. Fe O with 0<δ<1/3, could be formed. Ion beam channelling has been used to examine the epitaxy of the films. It was found that the films grow coherent on MgO(100). 57 2 3 4 2 3 3-δ 4

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  • Magnetite Fe3-δO4 : a Stoichiometry and Structure Analysis of MBE Grown Thin Films Using NO2 as the Oxidising Source

    Journal de Physique. IV France   7 ( 1 )   C1-601-602   1997年3月

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  • Li doping to the 2212 phase in the Bi-Sr-Ca-Cu-O system

    Masashi Fujiwara, Masahiro Nagae, Yoshihiro Kusano, Tatsuo Fujii, Jun Takada

    Physica C: Superconductivity and its Applications   274 ( 3-4 )   317 - 322   1997年2月

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    The effects of Li doping on the formation process of the 2212 phase in the Bi-Sr-Ca-Cu-O system, and its structural and superconducting features were studied. Samples with nominal compositions of Bi : Sr: Ca: Cu: Li = 2: 1.5: 1.5: 2: x where 0 ≤ x ≤ 0.6 were heated in air at temperatures ranging between 560°C and 850°C. Li doping greatly promoted the formation of the 2212 phase; the monophasic samples were rapidly obtained for x ≤ 0.4 by firing even at 730°C, which is about 100°C lower than that of the non-doped 2212 phase. A newly found oxide phase containing Li, which was formed below 710°C, is considered to play an important role as a precursor to accelerate the formation of the 2212 phase. The Li content in the monophasic samples determined by ICP analysis decreased to about a half of the nominal composition due to partial Li escape during heating. Monophasic composition range of the Li-doped 2212 phase was 0 ≤ y ≤ 0.19 as Bi Sr Ca Cu Li O . Increase in both lattice parameter c and oxygen content z with increasing Li content y in the 2212 phase was accompanied with a rise of T up to 90 K. 2 1.5 1.5 2 y z c

    DOI: 10.1016/S0921-4534(96)00689-2

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  • 電極反応によるBi-2212相へのLiドープ

    粉体および粉末冶金   44 ( 2 )   142 - 146   1997年2月

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    記述言語:日本語  

    DOI: 10.2497/jjspm.44.142

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  • 活性化反応蒸着法によるZnO系透明導電膜の作製と物性

    藤原 貴, 藤井 達生, 難波 徳郎, 高田 潤, 三浦 嘉也

    岡山大学環境理工学部研究報告   2 ( 1 )   121 - 129   1997年1月

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    記述言語:日本語   出版者・発行元:岡山大学環境理工学部  

    Zinc oxide films were prepared on silica glass substrates by the use of an r.f. activated reactive evaporation (ARE) method, and were examined by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrical conductivity of the films and the doping effect of Al ions were also investigated. XRD measurements indicate that the films were c-axis oriented and that an r.f. plasma of Zn and O was necessary for the ZnO film deposition. Substrate temperature, oxygen gas pressure, evaporation rate, r.f. power and Al doping amount affect the c-axis orientation, the growth rate, the microstructure of the films and electrical conductivity. Optimum conditions with a fine texture of the surface and having good ctystallinity as well as good conductivity (≒10(-4)Ω・cm) were as follows : the substrate temperature; 200℃, the total evaporation rate; 1.0Å/s, the oxygen pressure; 2.0×10(-4) Torr, the r.f. power; 250W and the Al evaporation rare ratio; 2~6%. The films with 1.0×10(-3)Ω・cm were prepared at 50℃ for the substrate temperature.

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  • In situ RHEED and XPS studies of epitaxial thin α-Fe<inf>2</inf>O<inf>3</inf>(0001) films on sapphire

    T. Fujii, D. Alders, F. C. Voogt, T. Hibma, B. T. Thole, G. A. Sawatzky

    Surface Science   366 ( 3 )   579 - 586   1996年11月

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    In situ RHEED and XPS measurements of epitaxial α-Fe O (0001) films are reported as a function of the number of deposited monolayers. The films were prepared on α-Al O (0001) substrates by MBE. The RHEED patterns suggest that layer-by-layer growth of α-Fe O (0001) occurs for the first few monolayers. Subsequently, the growth mode changes to three-dimensional growth. The in-plane lattice constant of the first monolayer of α-Fe O (0001) is expanded relative to that of the bulk, although in the case of lattice matching between α-Al O and α-Fe O a contraction would be expected. This can be explained by assuming a basic hexagonal structure for the first monolayer with a random distribution of ferric ions over the octahedral sites between the close-packed oxygen layers. Beyond the first monolayer, the ordered corundum structure is formed. The lineshapes of the XPS Fe 2p core level spectra are also found to be thickness-dependent. The deviation of the Madelung potential at the surface shifts the positions of the Fe 2p peaks to lower binding energies. For the first few monolayers, the satellite intensity is reduced because the interplanar contraction leads to a shorter Fe-O distance. 2 3 2 3 2 3 2 3 2 3 2 3

    DOI: 10.1016/0039-6028(96)00844-8

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  • Fe_3O_4/MO(M=Co, Ni)人工格子の磁性・電子構造

    藤井 達生, 浅岡 裕史, 高田 潤

    日本物理学会講演概要集. 秋の分科会   1996 ( 3 )   72 - 72   1996年9月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • バナジウムカルコゲナイドの磁気転移

    中西 真, 藤井 達生, 高田 潤, 吉村 一良, 小菅 皓二, 後藤 恒昭

    日本物理学会講演概要集. 秋の分科会   1996 ( 3 )   107 - 107   1996年9月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • Growth and properties of epitaxial iron oxide layers

    F. C. Voogt, T. Fujii, T. Hibma, M. Hoefman, P. J.M. Smulders, G. H. Wijnja, G. L. Zhang, L. Niesen

    Hyperfine Interactions   97-98 ( 1 )   99 - 108   1996年

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    Epitaxial layers of iron oxides have been grown on a MgO(001) substrate by evaporating natural Fe or 57Fe from Knudsen cells in the presence of a NO flow directed to the substrate. The resulting layers have been investigated in situ with LEED, RHEED, AES and XPS and ex situ with CEMS and ion beam analysis. For substrate temperatures between 200 and 400°C we observe RHEED oscillations during deposition, indicative of layer-by-layer growth. By adjusting the flux of NO at the surface, all stable and mctastable cubic phases in the Fe-O system could be grown: FeO (wustite), Fe O (magnetite), γ-Fe O (maghcmitc) and solid solutions between the latter two phases. Rutherford backscattering spectra show a relatively high minimum yield in the channel directions. © J.C. Baltzer AG, Science Publishers. 2 2 3 4 2 3

    DOI: 10.1007/bf02150170

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  • Magnetic properties of iron-oxide small particles prepared on aluminum and MgO(100)

    K. Fukumura, A. Nakanishi, T. Fujii, T. Kobayashi

    Journal of Magnetism and Magnetic Materials   145 ( 1-2 )   175 - 180   1995年3月

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    Magnetic properties of small particles of iron oxide on an aluminum foil and a single crystal of MgO are studied by conversion electron Mössbauer spectroscopy (CEMS) at low temperature. The average thickness of the oxide layers is 3.0 nm on aluminum and 1.2 nm on MgO. The CEMS spectra are observed at 15-300 K with a gas-filled proportional counter which was developed in our laboratory. The hyperfine fields in the surface layer and in the core of the particles are separated. The diameter and magnetic anisotropy energy constant are 3.7 nm and 0.87 × 10 J/m , and 3.5 nm and 2.4 × 10 J/m , respectively, for small particles on aluminum and MgO. The large difference in the anisotropy constants of small particles on aluminum and MgO is attributed to the enhanced surface anisotropy, which may be caused by diffusion of magnesium ions into the lattice of iron oxide. The superparamagnetic blocking temperatures of these particles are 71 and 94 K, respectively. © 1995. 5 3 5 3

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  • 反応性蒸着法によるFe3O4/CoO人工格子の作製と物性

    粉体および粉末冶金   42 ( 1 )   34 - 39   1995年

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    記述言語:英語  

    DOI: 10.2497/jjspm.42.34

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  • Spin-flip anomalies in epitaxial α-Fe<inf>2</inf>O<inf>3</inf> films by Mössbauer spectroscopy

    Tatsuo Fujii, Mikio Takano, Rintaro Kakano, Yasuhito Isozumi, Yoshichika Bando

    Journal of Magnetism and Magnetic Materials   135 ( 2 )   231 - 236   1994年7月

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    記述言語:英語  

    The spin-flip transition of 1000 Å-thick α-Fe O films was investigated by conversion electron Mössbauer spectroscopy from 2.5 to 673 K. The films were epitaxially formed on α-Al O single-crystalline substrates by a reactive vapor deposition method. Not only the transition temperature but also the spin axis were found to strongly depend upon the film orientation, probably as a result of anisotropic lattice strains caused by interactions with the substrate. For a (102)-oriented film the transition takes place at about 400 K, much higher the Morin transition temperature (260 K) of the free crystal, and the spin axis lying within the (102) plane above 400 K changes almost normal to the plane at room temperature and below: the normal makes 57.6° with the spin axis of the free crystal. A (001)-oriented film, on the other hand, does not show any transition at least down to 2.5 K. © 1994. 2 3 2 3

    DOI: 10.1016/0304-8853(94)90351-4

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  • Characteristics of titanium oxide films deposited by an activated reactive evaporation method

    Tatsuo Fujii, Naoki Sakata, Jun Takada, Yoshinari Miura, Yoshihiro Daitoh, Mikio Takano

    Journal of Materials Research   9 ( 6 )   1468 - 1473   1994年6月

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    記述言語:英語  

    Titanium di- and sesquioxide films were epitaxially grown on the (001) surface of sapphire single-crystalline substrates by an activated reactive evaporation method. Formation range for each titanium oxide was determined as a function of oxygen pressure (Po2) by means of x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Films prepared at Po^.OX 10 4 Torr were stoichiometric (lOO)-oriented rutile of Ti02, and with decreasing Po2 they would accommodate more and more Ti3+ ions in the rutile structure. At P02 = 0.6 X 10~4 Torr, on the other hand, (OOl)-oriented Ti203 was formed and an electrical transition was clearly detected at about 400 K. However, the large lattice mismatch between the substrate and these films leads to a periodic introduction of misfit dislocations in the case of the Ti02 films and a mixing of stacking sequences for the Ti203 films. © 1994, Materials Research Society. All rights reserved.

    DOI: 10.1557/JMR.1994.1468

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  • Surface and interface properties of epitaxial Fe<inf>3</inf>O<inf>4</inf> films studied by Mössbauer spectroscopy

    Tatsuo Fujii, Mikio Takano, Rintaro Katano, Yasuhito Isozumi, Yoshichika Bando

    Journal of Magnetism and Magnetic Materials   130 ( 1-3 )   267 - 274   1994年2月

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    記述言語:英語  

    Stoichiometric Fe O films have formed epitaxially on α-Al O and MgO single-crystal substrates by a reactive vapor deposition method. In order to apply conversion electron Mössbauer spectroscopy depth-selectively, a 5-7 Åthick probe layer containing Fe was formed at various depths in inactive Fe O matrix films. At the topmost surfaces and also at the interfaces, the essential electronic features of bulk Fe O are retained, including a rapid electron hopping between the Fe and Fe ions at B sites. Minor depth-dependent changes are confined to a few outermost atomic layers, and the changes depend on the orientation and the lattice mismatch with the substrate. For (111) growth on α-Al O , the surface layer seems to be strongly relaxed to reduced the electric polarization, while a high density of defects seems to be concentrated at the interface with α-Al O . For (001) growth on MgO, the surface retains the spinel lattice though slightly oxidized, while the interface with MgO has good crystallinity and stoichiometry. An enhanced thermal fluctuation of the Fe -spins in contact with the MgO substrate and in the topmost surface layer can be seen in their reduced magnetic hyperfine field at 300 K. © 1994. 3 4 2 3 3 4 3 4 2 3 2 3 57 56 2+ 3+ 3+

    DOI: 10.1016/0304-8853(94)90683-1

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  • Characteristics of titanium oxide films deposited by an activated reactive evaporation method

    Tatsuo Fujii, Naoki Sakata, Jun Takada, Yoshinari Miura, Yoshihiro Daitoh, Mikio Takano

    Journal of Materials Research   9 ( 6 )   1468 - 1473   1994年

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    記述言語:英語  

    Titanium di- and sesquioxide films were epitaxially grown on the (001) surface of sapphire single-crystalline substrates by an activated reactive evaporation method. Formation range for each titanium oxide was determined as a function of oxygen pressure (Po2) by means of x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Films prepared at Po^.OX 10 4 Torr were stoichiometric (lOO)-oriented rutile of Ti02, and with decreasing Po2 they would accommodate more and more Ti3+ ions in the rutile structure. At P02 = 0.6 X 10~4 Torr, on the other hand, (OOl)-oriented Ti203 was formed and an electrical transition was clearly detected at about 400 K. However, the large lattice mismatch between the substrate and these films leads to a periodic introduction of misfit dislocations in the case of the Ti02 films and a mixing of stacking sequences for the Ti203 films. © 1994, Materials Research Society. All rights reserved.

    DOI: 10.1557/JMR.1994.1468

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  • Surface and interface properties of epitaxial Fe3O4 films studied by Mössbauer spectroscopy

    Tatsuo Fujii, Mikio Takano, Rintaro Katano, Yasuhito Isozumi, Yoshichika Bando

    Journal of Magnetism and Magnetic Materials   130 ( 1-3 )   267 - 274   1994年

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    記述言語:英語  

    Stoichiometric Fe3O4 films have formed epitaxially on α-Al2O3 and MgO single-crystal substrates by a reactive vapor deposition method. In order to apply conversion electron Mössbauer spectroscopy depth-selectively, a 5-7 Åthick probe layer containing 57Fe was formed at various depths in inactive 56Fe3O4 matrix films. At the topmost surfaces and also at the interfaces, the essential electronic features of bulk Fe3O4 are retained, including a rapid electron hopping between the Fe2+ and Fe3+ ions at B sites. Minor depth-dependent changes are confined to a few outermost atomic layers, and the changes depend on the orientation and the lattice mismatch with the substrate. For (111) growth on α-Al2O3, the surface layer seems to be strongly relaxed to reduced the electric polarization, while a high density of defects seems to be concentrated at the interface with α-Al2O3. For (001) growth on MgO, the surface retains the spinel lattice though slightly oxidized, while the interface with MgO has good crystallinity and stoichiometry. An enhanced thermal fluctuation of the Fe3+-spins in contact with the MgO substrate and in the topmost surface layer can be seen in their reduced magnetic hyperfine field at 300 K. © 1994.

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  • Spin-flip anomalies in epitaxial α-Fe2O3 films by M(]E88D8[)ssbauer spectroscopy

    Journal of Magnetism and Magnetic Materials   135 ( 2 )   231 - 236   1994年

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  • Operation of a cryogenic conversion electron proportional counter under strong magnetic fields

    Tatsuo Fujii, Nobuyoshi Hosoito, Rintaro Katano, Yasuhito Isozumi

    Nuclear Inst. and Methods in Physics Research, B   76 ( 1-4 )   207 - 209   1993年4月

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    A new helium-filled proportional counter was constructed for conversion electron Mössbauer spectroscopy under strong magnetic fields. The counter was specially designed to be inserted into superconducting electromagnets placed at the bottom of a liquid helium cryostat. The operation of the counter was stable enough in magnetic fields up to 3 T at 4.2 K and it seemed to be little influenced by the strong magnetic field. A high performance of the present counter was demonstrated by observing a field-induced magnetic spin rotation of an α-Fe film. © 1993.

    DOI: 10.1016/0168-583X(93)95182-5

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  • 31p-PSB-46 Fe_3O_4/MO酸化物人工格子の作製

    藤井 達生, 坂本 正勝, 浅野 光洋, 難波 徳郎, 尾坂 明義, 高田 潤, 三浦 嘉也

    日本物理学会講演概要集. 年会   48 ( 3 )   121 - 121   1993年3月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • Preparation of Fe<inf>3</inf>O<inf>4</inf>/MgO Artificial Superlattices by Activated Reactive Evaporation Method

    Masakatsu Sakamoto, Mitsuhiro Asano, Tatsuo Fujii, Tokuro Nanba, Akiyoshi Osaka, Yoshinari Miura, Jun Takada

    journal of the japan society of powder and powder metallurgy   39 ( 11 )   985 - 988   1992年7月

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    記述言語:英語  

    DOI: 10.2497/jjspm.39.985

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  • Preparation of Fe<inf>3</inf>O<inf>4</inf> Single-crystalline Films by Reactive Evaporation Method

    F. Tatsuo, Sakamoto Masakatsu, A. Mitsuhiro, N. Tokuro, O. Akiyoshi, M. Yoshinari, T. Jun, S. Ken-ichi, T. Takahito, B. Yoshichika

    journal of the japan society of powder and powder metallurgy   39 ( 11 )   981 - 984   1992年7月

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    DOI: 10.2497/jjspm.39.981

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  • Preparation of Fe3O4 Single-crystalline Films by Reactive Evaporation Method

    Fujii Tatsuo, Sakamoto Masakatsu, Asano Mitsuhiro, Nanba Tokuro, Osaka Akiyoshi, Miura Yoshinari, Takada Jun, Shimura Ken-ichi, Terashima Takahito, Bando Yoshichika

    journal of the japan society of powder and powder metallurgy   39 ( 11 )   981 - 984   1992年

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    DOI: 10.2497/jjspm.39.981

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  • Preparation of Fe3O4/MgO Artificial Superlattices by Activated Reactive Evaporation Method

    Masakatsu Sakamoto, Mitsuhiro Asano, Tatsuo Fujii, Tokuro Nanba, Akiyoshi Osaka, Yoshinari Miura, Jun Takada

    journal of the japan society of powder and powder metallurgy   39 ( 11 )   985 - 988   1992年

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    DOI: 10.2497/jjspm.39.985

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  • Mössbauer Spectroscopic Study of Surface and Interface Properties of Epitaxial Fe<inf>3</inf>O<inf>4</inf> Films

    Tatsuo Fujii, Jun Takada, Yoshinari Miura, Mikio Takano, Yoshichika Bando

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   39 ( 2 )   143 - 146   1992年

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    記述言語:英語  

    Stoichiometric Fe3O4 films have been epitaxially formed on both =α-Al2O3 and MgO single-crystalline substrates by a reactive vapor deposition method. A few-A-thick probe layer containing 57Fe was formed at a desired depth of an inactive S6Fe3O4 matrix film to apply a depth selective Mossbauer spectroscopy. Even at the topmost layer and also at the interface, the electronic state retained the essential features of Fe304 bulk so that the Verwey transition was clearly detected. Any minor depth-dependent changes in electronic state were confined in a few outermost atomic layers. The nature of the changes depended on the orientation of the films and the lattice mismatch between the substrate and the film. © 1992, Japan Society of Powder and Powder Metallurgy. All rights reserved.

    DOI: 10.2497/jjspm.39.143

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  • 活性化反応蒸着法によるFe3O4/MgO超格子薄膜の作製

    粉体および粉末冶金   39 ( 11 )   985 - 988   1992年

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    DOI: 10.2497/jjspm.39.985

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  • 活性化反応蒸着法によるFe3O4単結晶薄膜の合成

    粉体および粉末冶金   39 ( 11 )   981 - 984   1992年

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    記述言語:英語  

    DOI: 10.2497/jjspm.39.981

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  • メスバウァー分光法によるエピタキシャルFe3O4薄膜の表面及び界面層の研究

    粉体および粉末冶金   39 ( 2 )   143 - 146   1991年

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  • Mössbauer Study on the Magnetic Properties of a Single Crystalline Bi<inf>3</inf>Fe<inf>5</inf>O<inf>12</inf> Film

    Tatsuo Fujii, Mikio Takano, Yoshichika Bando, Takashi Okuda

    Journal of the Japan Society of Powder and Powder Metallurgy   38 ( 3 )   427 - 430   1991年

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    Very recently, an artificial new material “bismuth iron garnet” was prepared for the first time with a reactive ion-beam-sputterring method. A magnetic characterization of this single crystalline garnet film was achieved by applying conversion electron Mössbauer spectroscopy (CEMS). To examine the temperature dependence of sublattice magnetization, CEMS measurments were made at 6, 78, 290, and 670 K, i.e. in both the ferrimagnetic and paramagnetic regions. The magnetic and quadrupole hyperfine interactions as compared with YIG indicated continuous effects of lattice expansion owing to the large spherical size of Bi ions. The temperature dependence of sublattice magnetization has been explained by the two-sublattice molecular field model with a molecular field constant N slightly modified from that of YIG. © 1991, Japan Society of Powder and Powder Metallurgy. All rights reserved. 3+ ad

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  • Conversion electron Mössbauer spectroscopy of a single crystalline Bi<inf>3</inf>Fe<inf>5</inf>O<inf>12</inf> film

    T. Fujii, M. Takano, R. Katano, Y. Bando, Y. Isozumi, T. Okuda

    Journal of Magnetism and Magnetic Materials   92 ( 2 )   261 - 264   1990年11月

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    A magnetic characterization of a single crystalline bismuth iron garnet film was done by applying conversion electron Mössbauer spectroscopy (CEMS). To examine the temperature dependence of sublattice magnetization, CEMS measurements were made at 6, 78, 290 and 670 K, i.e. in both the ferrimagnetic and paramgnetic regions. The magnetic and quadrupole hyperfine interactions as compared with those in other garnets like YIG indicated continuous effects of lattice expansion. The temperature dependence of the sublattice magnetization has been explained at the present stage by the two-sublattice molecular field model using parameters slightly modified from those of YIG. © 1990.

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  • 31a-H-7 CEMSによるマグネタイト単結晶薄膜の研究(II)

    藤井 達生, 高野 幹夫, 片野 林太郎, 坂東 尚周, 五十棲 泰人

    年会講演予稿集   45 ( 3 )   67 - 67   1990年3月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • CEMS study of the growth and properties of Fe<inf>3</inf>O<inf>4</inf> films

    T. Fujii, M. Takano, R. Katano, Y. Bando, Y. Isozumi

    Journal of Crystal Growth   99 ( 1-4 )   606 - 610   1990年1月

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    Stoichiometric Fe O films have been epitaxially formed on both α-Al O and MgO single-crystalline substrates by a reactive vapor deposition method. Their crystalline qualities were examined by various methods including conversion electron Mössbauer spectroscopy (CEMS). A large lattice mismatch of Fe O with the α-Al O substrate resulted in a granular particle growth. But with Fe O /MgO, where the mismatch was only 0.3%, the structural and magnetic properties were found to be very sensitive to an excellent interfacial lattice matching. © 1990. 3 4 2 3 3 4 2 3 3 4

    DOI: 10.1016/0022-0248(90)90592-9

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  • Depth selective Mössbauer spectroscopic study of Fe<inf>3</inf>O <inf>4</inf> epitaxial films

    T. Fujii, M. Takano, R. Katano, Y. Bando, Y. Isozumi

    Journal of Applied Physics   68 ( 4 )   1735 - 1740   1990年

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    記述言語:英語  

    Several (111) oriented Fe O films containing a 5-Å-thick Fe O probe layer at or below the surface were grown epitaxially on the α-Al O (0001) surface by a reactive vapor deposition method. Conversion electron Mössbauer spectroscopy was applied at 6, 78, and 300 K by using a recently developed helium-filled proportional counter. The well-crystallized surface has been found to be surprisingly stable even in air as characterized by the Mössbauer parameters that are almost the same as for the bulk. Moreover, the Verwey transition was detected clearly even in the 5-Å-thick surface layer. However, the ferrous components seem to have changed their Mössbauer parameters probably because of their sensitivity to any crystalline field modifications in the surface. Generally speaking, the quality of epitaxial Fe O films is very high: Any unusual surface state, if present, is confined in a shallow depth of ≤ 5 Å. 56 57 3 4 3 4 2 3 3 4

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  • Depth selective Mössbauer spectroscopic study of Fe3O 4 epitaxial films

    T. Fujii, M. Takano, R. Katano, Y. Bando, Y. Isozumi

    Journal of Applied Physics   68 ( 4 )   1735 - 1740   1990年

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    記述言語:英語  

    Several (111) oriented 56Fe3O4 films containing a 5-Å-thick 57Fe3O4 probe layer at or below the surface were grown epitaxially on the α-Al 2O3 (0001) surface by a reactive vapor deposition method. Conversion electron Mössbauer spectroscopy was applied at 6, 78, and 300 K by using a recently developed helium-filled proportional counter. The well-crystallized surface has been found to be surprisingly stable even in air as characterized by the Mössbauer parameters that are almost the same as for the bulk. Moreover, the Verwey transition was detected clearly even in the 5-Å-thick surface layer. However, the ferrous components seem to have changed their Mössbauer parameters probably because of their sensitivity to any crystalline field modifications in the surface. Generally speaking, the quality of epitaxial Fe3O4 films is very high: Any unusual surface state, if present, is confined in a shallow depth of ≤ 5 Å.

    DOI: 10.1063/1.346602

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  • 29a-PS-81 CEMSによるマグネタイト単結晶薄膜の研究(磁性(C, F, H))

    藤井 達生, 高野 幹夫, 片野 林太郎, 坂東 尚周, 五十棲 泰人

    年会講演予稿集   44 ( 3 )   82 - 82   1989年3月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • Helium-filled proportional counter for low-temperature operation (1.75-4.2 K) and its application to cryogenic resonance-electron Mössbauer spectroscopy II

    Yasuhito Isozumi, Shin Ito, Tatuo Fujii, Rintaro Katano

    Review of Scientific Instruments   60 ( 10 )   3262 - 3264   1989年

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    記述言語:英語  

    The operation of the helium-filled proportional counter (HFPC) has been investigated at low temperatures below liquid-helium temperature, 4.2 K. It has been found that the gas gain as a function of the anode voltage is not appreciably changed by the temperature of the filling gas, but continuous electric discharges are induced at lower anode voltages as the gas temperature is decreased. The present counter technique has been applied to resonance-electron Mössbauer spectroscopy in the temperature region below 4.2 K.

    DOI: 10.1063/1.1140562

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  • Preparation and characterization of (111)-oriented Fe<inf>3</inf>O <inf>4</inf> films deposited on sapphire

    T. Fujii, M. Takano, R. Katano, Y. Bando, Y. Isozumi

    Journal of Applied Physics   66 ( 7 )   3168 - 3172   1989年

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    記述言語:英語  

    Films of various iron oxides including FeO, Fe O , and α-Fe O were formed on the α-Al O (0001) surface by a reactive vapor deposition method and characterized by x-ray diffraction and conversion electron Mössbauer spectroscopy (CEMS). The formation range for each phase was determined as a function of the substrate temperature (T ) and oxygen partial pressure (P ). Typically, the deposition of (111)-oriented epitaxial magnetite films could be performed at low temperatures of T =523∼623 K and P =1.0-5.0×10 Torr. Good stoichiometry of the as-grown films were confirmed by CEMS, and the Verwey transition was clearly detected by measurements of resistivity and CEMS down to 77 K. However, the large lattice mismatch between the substrate and Fe O resulted in a columnar particle growth. The initially grown phase on such a mismatched substrate was specifically characterized by depositing the Mössbauer active isotope, Fe, only at the deepest layers. On the other hand, by depositing Fe only in the topmost layers, surface layers of well-crystallized films have been found to be rather stable against oxidation. 3 4 2 3 2 3 s O2 s O2 3 4 -4 57 57

    DOI: 10.1063/1.344154

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  • Preparation and characterization of (111)-oriented Fe3O 4 films deposited on sapphire

    T. Fujii, M. Takano, R. Katano, Y. Bando, Y. Isozumi

    Journal of Applied Physics   66 ( 7 )   3168 - 3172   1989年

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    記述言語:英語  

    Films of various iron oxides including FeO, Fe3 O4, and α-Fe2 O3 were formed on the α-Al 2 O3 (0001) surface by a reactive vapor deposition method and characterized by x-ray diffraction and conversion electron Mössbauer spectroscopy (CEMS). The formation range for each phase was determined as a function of the substrate temperature (Ts) and oxygen partial pressure (PO2). Typically, the deposition of (111)-oriented epitaxial magnetite films could be performed at low temperatures of Ts =523∼623 K and PO2 =1.0-5.0×10-4 Torr. Good stoichiometry of the as-grown films were confirmed by CEMS, and the Verwey transition was clearly detected by measurements of resistivity and CEMS down to 77 K. However, the large lattice mismatch between the substrate and Fe 3 O4 resulted in a columnar particle growth. The initially grown phase on such a mismatched substrate was specifically characterized by depositing the Mössbauer active isotope, 57 Fe, only at the deepest layers. On the other hand, by depositing 57 Fe only in the topmost layers, surface layers of well-crystallized films have been found to be rather stable against oxidation.

    DOI: 10.1063/1.344154

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  • Helium-filled proportional counter for low-temperature operation (1.75-4.2 K) and its application to cryogenic resonance-electron Mössbauer spectroscopy II

    Yasuhito Isozumi, Shin Ito, Tatuo Fujii, Rintaro Katano

    Review of Scientific Instruments   60 ( 10 )   3262 - 3264   1989年

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    記述言語:英語  

    The operation of the helium-filled proportional counter (HFPC) has been investigated at low temperatures below liquid-helium temperature, 4.2 K. It has been found that the gas gain as a function of the anode voltage is not appreciably changed by the temperature of the filling gas, but continuous electric discharges are induced at lower anode voltages as the gas temperature is decreased. The present counter technique has been applied to resonance-electron Mössbauer spectroscopy in the temperature region below 4.2 K.

    DOI: 10.1063/1.1140562

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講演・口頭発表等

  • (SrCa)(FeCo)12-δO19-η における異方性磁場及び 76GHz 近傍での磁気共鳴の測定

    兵頭 一茂, 中西 真, 狩野 旬, 藤井 達生

    日本セラミックス協会2021年年会 

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    開催年月日: 2021年3月23日 - 2021年3月25日

    会議種別:口頭発表(一般)  

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  • パイプ状多孔質酸化鉄上への水熱法による MFI 型ゼオライトの合成

    張 斉, 中西 真, 藤井達生

    日本セラミックス協会2021年年会 

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    開催年月日: 2021年1月23日 - 2021年1月25日

    会議種別:ポスター発表  

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  • 鉄系複酸化物ナノ粒子の合成と Li イオン二次電池への応用

    渡辺 穂香, 藤井 達生

    第59回セラミックス基礎科学討論会  2021年1月7日 

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    開催年月日: 2021年1月7日 - 2021年1月8日

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  • 鉄酸化沈殿物を鋳型としたチタニアナノ粒子の作製と特性評価

    小田智尋, 田村勝徳, 藤井 達生

    第59回セラミックス基礎科学討論会 

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    開催年月日: 2021年1月7日 - 2021年1月8日

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  • In situ M?ssbauer analysis of bacterial iron-oxide nano-particles for lithium-ion battery 招待

    Ryo Sakuma, Hideki Hashimoto, Tatsuo Fujii, Jun Takada, Naoaki Hayashi, Mikio Takano

    5th Mediterranean Conference on the Applications of the M?ssbauer Effect 

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    開催年月日: 2019年5月19日 - 2019年5月23日

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    開催地:Montpellier, France  

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  • スパッタ法によるFe3O4下地層上へのエピタキシャルYbFe2O4薄膜の作製 招待

    藤井達生

    第28回日本MRS年次大会 

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    開催年月日: 2018年12月18日 - 2018年12月20日

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    開催地:北九州市  

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共同研究・競争的資金等の研究

  • 電子強誘電体の逐次電荷秩序相転移の研究

    研究課題/領域番号:22H01942  2022年04月 - 2025年03月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    池田 直, 藤井 達生, 沖本 洋一, 藤原 孝将

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    配分額:17420000円 ( 直接経費:13400000円 、 間接経費:4020000円 )

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  • 非平衡電子構造解析に基づく蓄電池カソード配位子電荷移動の安定化

    研究課題/領域番号:18H03929  2018年04月 - 2022年03月

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    内本 喜晴, 田中 優実, 藤井 達生, 折笠 有基, 大石 昌嗣

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    配分額:43030000円 ( 直接経費:33100000円 、 間接経費:9930000円 )

    リチウムイオンの挿入・脱離時に酸化物イオンの電荷補償が起こるリチウム過剰系酸化物正極材料について、遷移金属カチオンではなく、アニオンの電荷補償に着目し、operando軟X線吸収分光法と高エネルギーX線コンプトン散乱法を用いて、その機構解明を行うことで、アニオン制御による材料の設計指針を確立した。遷移金属カチオンと酸化物イオンとの共有結合性またはイオン結合性のいずれかが極端に強い場合に、酸化物イオンが可逆的に電荷補償に寄与できることを見出した。従来酸化物を中心に研究開発されてきた、リチウム過剰系材料の分野において、酸化物イオンの一部を窒化物イオンに置換することにより高容量が発現した。

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  • 三角格子系希土類鉄酸化物による常温マルチフェロ材料の創製

    研究課題/領域番号:18H02057  2018年04月 - 2022年03月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    藤井 達生, 池田 直, 狩野 旬

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    配分額:17550000円 ( 直接経費:13500000円 、 間接経費:4050000円 )

    次世代のマルチフェロイック材料として期待されているRFe2O4について、スパッタ法による単結晶薄膜の合成を試みた。その結果、Fe3O4バッファ層を介することでサファイア基板上のRFe2O4層の面内配向が30°回転すること、また、Fe3O4とRFe2O4を積層した場合も、同様に積層の順番に依存して、面内配向が回転することを見出した。くわえて、YSZ単結晶基板を使用した場合は、双晶ドメインを持たない、ほぼ完全にシングルドメインとなるRFe2O4薄膜を得ることができた。

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  • 表面構造緩和を活用した非磁性ナノ粒子への磁性付与

    研究課題/領域番号:26630319  2014年04月 - 2017年03月

    日本学術振興会  科学研究費助成事業  挑戦的萌芽研究

    藤井 達生, 竹村 大樹, 安藤 大生, 狩野 旬, 中西 真

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    配分額:3900000円 ( 直接経費:3000000円 、 間接経費:900000円 )

    我々はバルクでは、磁化をほとんど示さないLaFeO3が、ナノ粒子化により非常に大きな磁化を持つことを見出した。これは、ナノ粒子化により、結晶の並進対称性が消失するとともに構造緩和が生じ、強磁性的相互作用が発現したためだと考えられる。そこで本研究では、LaFeO3ナノ粒子の構造及び磁気特性を系統的に評価することで、ナノ粒子化によるLaFeO3の巨大磁化発現機構を解明することを目的としている。その第一歩として、塩添加噴霧熱分解法を用いることで、均一な粒子径分布を持つLaFeO3ナノ粒子の合成条件を確立し、ナノ粒子の合成条件と構造、磁性との相関を明らかにした。

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  • 細菌が酸性環境で作る酸化鉄の制御と特徴解明、機能開拓と鉱山廃水処理への応用の試み

    研究課題/領域番号:26289261  2014年04月 - 2017年03月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    高田 潤, 藤井 達生, 宮田 直幸, 草野 圭弘

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    配分額:16250000円 ( 直接経費:12500000円 、 間接経費:3750000円 )

    特異な鉄酸化細菌を利用して行う新しい廃水処理方法の開発とその処理により形成する酸化鉄の機能開拓を目指して研究を展開した。得られた主な結果は次の通りである。(1)好酸性鉄酸化細菌単離菌”E10”を合成培地で培養し、種々の培養条件(pHと温度)で形成する酸化鉄(S相とG相)の種類とその量比、さらにそれらの酸化鉄、特にS相の特徴を明らかにした。(2)好酸性鉄酸化細菌単離菌” E10”を用いることにより、合成培地と同様に実鉱山坑廃水からFe2+イオンを効果的に除去できることを示した。(3)形成するオキシ酸化鉄は優れた重金属吸着機能(As(Ⅴ), Se(Ⅵ), Mo(Ⅵ))を持つことを明らかにした。

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  • 原子価制御による機能性鉄チタン複合酸化物薄膜の開拓

    研究課題/領域番号:23350092  2011年04月 - 2015年03月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    藤井 達生, 中西 真, 市川 和典, 高田 潤, 中西 真

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    配分額:20150000円 ( 直接経費:15500000円 、 間接経費:4650000円 )

    本研究では、ヘマタイト-イルメナイト固溶体を中心とする混合原子価酸化物について単相試料を合成し、その磁性や電子状態を明らかにするとともに、それら酸化物の単結晶状薄膜を作製し、結晶配向性や格子歪みがその構造や電荷移動に及ぼす影響を解明・制御することを試みた。その結果、ヘマタイト-イルメナイト固溶体薄膜の微細構造や電気輸送特性は、薄膜の配向面により大きく異なることが明らかとなり、その原因として、結晶構造そのものが持つ異方性に加えて、薄膜と基板と間のミスフィットが大きく影響することを明らかにした。

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  • 微生物由来非晶質ナノサイズ・バイオ酸化鉄のLiイオン電池革新的正極活物質への展開

    研究課題/領域番号:23360309  2011年04月 - 2014年03月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    高田 潤, 藤井 達生, 中西 真, 草野 圭弘, 菅野 了次

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    配分額:18980000円 ( 直接経費:14600000円 、 間接経費:4380000円 )

    次世代のLiイオン二次電池で求められている高性能化および大幅な低コスト化の実現を目指して、自然界の溝などに生息する鉄酸化細菌が作る非晶質のナノサイズのバイオ酸化鉄に注目して、その特徴の解明とLi充放電特性の評価、および充放電機構について検討した。その結果、このバイオ酸化鉄は人工作製が困難な新しい材料であり、高容量でサイクル特性の優れた正極活物質であることを見出した。さらに、この微生物由来酸化鉄のLiの充放電機構は、Fe3+ ⇔ Fe2+ の可逆反応によるものであることを明らかにした。

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  • バクテリアが作るナノ・バイオ酸化鉄のキャラクタリゼーションとLiイオン充放電挙動

    研究課題/領域番号:19360300  2007年 - 2008年

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    高田 潤, 藤井 達生, 中西 真, 菅野 了次, 草野 圭弘

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    配分額:20670000円 ( 直接経費:15900000円 、 間接経費:4770000円 )

    バクテリア(鉄細菌)が作るチューブ状酸化鉄の特徴を詳細に検討した結果、非常にユニークな酸化鉄材料であることを明らかにした。即ち、直径が約1μmの中空チューブ状の形状で、非晶質構造を有し、3nmの1次粒子から成り、化学組成も特徴ある。さらに、この微生物由来バイオ酸化鉄はLiイオンについて優れた充放電特性を示すことを見出した。

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  • 状態図的研究に基づく六方晶フェライト系GHz帯対応高周波デバイス材料の創製

    研究課題/領域番号:17360326  2005年 - 2006年

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    高田 潤, 藤井 達生, 和田 修己, 中西 真, 草野 圭弘

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    配分額:15400000円 ( 直接経費:15400000円 )

    本研究では、現在も不明な点の多い一連のフェロックスプラナー型フェライトの本質(合成条件・固溶組成・元素置換効果や基本的電磁気特性とその支配因子)の解明研究と、これらを基礎として新規なGHz帯域電磁波用磁性薄膜材料および広帯域GHz帯域複合型電磁波吸収焼結体材料の創製の基礎研究を行うことを目的とした。
    まず、様々なフェロックスプラナー型フェライト相の単相試料の合成条件を検討し、状態図的検討を行った。その結果、1000℃および1200℃での各相の固溶組成域を明らかにした。その過程で、Y型およびZ型の生成機構メカニズムをX線回折測定により検討し、そのモデルを提案した。更に、六方晶フェライトの構造や透磁率などの電磁気特性と組成との関係を明らかにした。
    これらの結果を基に、錯体重合法によるフェロックスプラナー型フェライトの高配向磁性薄膜の作製条件を検討し、微量元素の影響と生成メカニズムを検討した。また、磁性材料であるY型フェライトと誘電材料であるSiCを複合化することにより、磁性損失と誘電損失を兼備した広帯域GHz帯電磁波吸収材料の作製を試みた。その結果、複合化条件を最適化することで、3.5〜6.5GHzという広い周波数範囲で-20dBより大きな吸収量を示す材料の作製に成功した。従来はトレードオフの関係にあると見られた吸収量と帯域幅の両者を共に満足させており、また周波数域が現在利用の盛んな5GHzを中心としたGHz帯域に制御できたことは大きな成果である。

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  • 微生物が常温で作るナノサイズ酸化鉄のキャラクタリゼーションとその応用の試み

    研究課題/領域番号:17651071  2005年 - 2006年

    日本学術振興会  科学研究費助成事業  萌芽研究

    高田 潤, 藤井 達生, 中西 真

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    配分額:3400000円 ( 直接経費:3400000円 )

    近年鉄細菌を用いた「バイオ浄水法」は、地下水の浄水法として実際に採用され、環境に優しい浄水法と注目されていて、今後急速に全国に広がると予想されている。このバイオ浄水法では、レプトシリックス鉄細菌が地下水中のFeイオンを体内に取込んで、細菌の体の周りにパイプ状酸化鉄鞘などの無機化合物を常温で生成し、濾過槽上部に褐色沈殿物を形成する。しかし、現在この酸化鉄鞘の詳細が全く不明かつ分離・回収が困難であるため、沈殿物を埋立廃棄しているのが現状であり、バイオ浄水法の利点が十分に活かされていない。
    そこで本研究では、先ず、鉄細菌が常温で作るパイプ状鉄細菌鞘酸化鉄やそれを構成する微細な酸化鉄微粒子を詳細に検討し、酸化鉄の種類、化学組成、微細構造を調査した。次に、浄水沈殿物からの分離・回収方法と鞘の増殖条件を検討した。更にパイプ状鉄細菌鞘酸化鉄の特性と再利用を検討した。その結果、欧文誌への論文1件と特許出願1件の成果を得た。
    得られた結果を要約すると以下の通りである。
    (1)パイプ状酸化鉄鞘は中空円柱状のマイクロチューブの形態を呈し、その内径と外径の平均値はそれぞれ1.1および1.4μm、長さは50〜200μmであることが明らかとなった。鞘の壁の厚さは平均0.15μmと非常に薄い。
    (2)このパイプ状酸化鉄の結晶構造は、21-ferrihydriteの構造に似ているが、より結晶性が低いことが判明した。
    (3)パイプ状酸化鉄鞘の壁は100nm以下の超微粒子から構成されており、それぞれの微粒子の組はほぼFe:Si:P=80:15:5であることを見出した。
    (4)このパイプ状酸化鉄はspin-glass的な磁気特性を示すことが明らかになった。
    (5)バイオ浄水沈殿物からの分離・回収方法を確立し、高純度サンプルを得ることに成功した。
    (6)このパイプ状酸化鉄鞘を加熱することによって、ヘマタイトへの変化と赤色顔料としての利用の可能性を見出した。

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  • 酸化鉄をベースとする循環型新規ナノデバイスの開発

    研究課題/領域番号:14350353  2002年 - 2004年

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    藤井 達生, 高田 潤, 中西 真

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    配分額:14900000円 ( 直接経費:14900000円 )

    本研究では、環境に優しいスピントロニクス材料の実現をめざし、まず、α-Fe_2O_3-FeTiO_3固溶体の中でも最も高い飽和磁化を示すFe_<1.2>Ti_<0.8>O_3組成の薄膜化を実施した。薄膜作製は、FeTi合金ターゲットを出発原料とする反応性スパッタ法により行なった。フェリ磁性を示す固溶体薄膜の実現には、結晶格子中でc軸方向にFe-rich層とTi-rich層が交互に積層した秩序相(空間群R3)の生成が必須であり、そのためには、成膜時の基板温度ならびに酸素分圧を厳密に制御する必要があることを明らかにした。
    次に、Fe_<1.2>Ti_<0.8>O_3薄膜の強磁性転移温度(T_C)を向上させることを目的に、高い反強磁性転移温度(T_N)をもつα-Fe_2O_3層をFe_<1.2>Ti_<0.8>O_3層と積層させた二層膜を作製し、層間の交換結合がFe_<1.2>Ti_<0.8>O_3層のT_Cに及ぼす影響を検討した。作製した二層膜は、基板温度550℃と高温であるにもかかわらず、非常にシャープな界面構造を有していた。また、二層膜のT_Cは約220Kであり、単相膜のT_C=約210Kと比較して、約10Kほど上昇させることに成功した。
    ところでFeTiO_3中の金属イオンは、Fe^<2+>とTi^<4+>の化学状態にあると考えられてきた。しかし、高分解能蛍光X線分析を実施したところ、FeTiO_3中のTiイオンの特性X線は、Ti^<3+>のものと非常に近いピーク形状を示しており、Ti^<3+>に近い化学状態にあることを明らかにした。また、XPSスペクトルからも、FeTiO_3は価電子帯のフェルミ端近傍に小さな状態密度を持っており、局在化したTi3d電子が存在する可能性を示した。よってα-Fe_2O_3-FeTiO_3固溶体の電子状態を正しく理解し、その磁性半導体として特質を明らかにするためには、より詳細な分光学的研究が必要であることを示した。

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  • 磁性単層膜と磁性2層膜における磁気異方性と磁気相互作用の研究

    研究課題/領域番号:13650761  2001年 - 2002年

    日本学術振興会  科学研究費助成事業  基盤研究(C)

    河本 修, 藤井 達生

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    配分額:2400000円 ( 直接経費:2400000円 )

    1.強磁性共鳴(FMR)の理論的研究を行った.FMRの理論式は古く知られていて,(1)SmitとBeljerによる厳密解と(2)Kittelによる近似解がある.有名なKittel式に用いる実効的反磁場係数を求める式が,彼の論文では正しくはないということが判明したので,正しい式を導出した.この新しい式によって,薄膜試料について,静磁場を膜面内に印加した次の6つの場合について共鳴式を求めた.それらは,(1)垂直一軸異方性,(2)面内一軸異方性,(3)立方晶(001)面,(4)立方晶(011)面,(5)立方晶(111)面,(6)斜め異方性である.
    2.実験としては,スパッタ法による単層膜(NiとCo)と2種類の結晶方位をもつエピタキシャルNiOによる2層膜(Ni/NiOとNiFe/NiO)の研究を行った
    (1)単層膜Niについて,(1)垂直異方性磁界H_<up>は,30mTorrの高Ar圧側で最も大きく,500Åで3.2kOeである.(2)低Ar圧側では,垂直磁気異方性は小さくなり,面内異方性が大きくなる.(3)残留磁化比M_r/M_sは,30mTorr以上の高Ar圧下で成膜中の印加磁界の平行方向,直角方向とも小さい値となり,面内異方性はみられなくなる.
    (2)単層膜Coについては,垂直異方性磁場(Hk)は,膜厚の減少伴い増加した.
    (3)2層膜Ni(500Å)/NiO(2000Å)とNiFe(500Å)/NiO(2000Å)について,(1)交換結合磁界H_<ex>は,NiO(100)面で最も大きく,Ni/NiO(100)で15.3 Oeである.(2)磁気抵抗効果Δρ/ρは,横効果(H⊥I)と縦効果(H//I)で値が大きく異なる.Ni/NiOでは,NiO(110)面で最も大きく,横効果(H⊥I)が0.22%,縦効果(H//I)が0.61%である.NiFe/NiOでは,NiO(100)面で最も大きく,横効果(H⊥I)が0.77%,縦効果(H//I)が0.81%である.

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  • インテグレーション超高周波デバイス用新規プラナ型フェライト薄膜の開発

    研究課題/領域番号:13025231  2001年

    日本学術振興会  科学研究費助成事業  特定領域研究(A)

    藤井 達生, 中西 真, 高田 潤

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    配分額:2100000円 ( 直接経費:2100000円 )

    電子通信機器の小型化・高性能化にともない、高い周波数帯域で優れた高周波磁気特性を有する磁性薄膜の開発が切望されている。しかし、スピネル型フェライトに代表される従来の磁性材料は、高周波で透磁率が急激に低下し使用できない。我々の研究グループでは、理論的に優れた高周波磁気特性を持つことが期待されるプラナ型フェライトに注目し、その薄膜の作製に世界ではじめて成功した。その特徴は、金属イオンが均一に分散固定される錯体重合法を用いて原料溶液を調製し、コーティング法により薄膜を作製した点である。そこで本研究では、プラナ型フェライト薄膜のグローバルインテグレーションを目標に、1.薄膜の膜質向上(平滑性・クラック等)を目的として、原料溶液組成の検討2.薄膜の焼成温度の低温化を目的として、基板材料の検討を行った。
    その結果、平滑かつクラックの無いプラナ型フェライト薄膜の作製のためには、原料溶液の混合比を、金属:クエン酸:エチレングリコール=1:4:12とすること、溶液のpHはpH<1とすること、そして粘度については10mPa・s以下とすることを明らかにした。また、種々の貴金属基板上に成膜した結果、プラナ型フェライト(Y型六方晶フェライト)の結晶化には、一般的に1000℃以上の高温焼成が必要とされるが、Ag基板を用いたときのみ特異的に結晶化温度が低下し、800℃の低温においてプラナ型フェライト薄膜が成長することを見出した。
    得られたプラナ型フェライト薄膜の高周波磁気特性を評価し、改善することが今後の課題である。

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  • 液相法による電磁環境対策用Ba系電波吸収フェライト材料の合成

    研究課題/領域番号:12450269  2000年 - 2002年

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    吉尾 哲夫, 藤井 達生, 高田 潤, 長江 正寛

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    配分額:14900000円 ( 直接経費:14900000円 )

    本研究では,近年の各種情報通信機器の発達に伴い社会環境問題となりつつある有害電波によって引き起こされる電波障害対策用としてのBa系電波吸収フェライト材料の合成法としてガラスセラミック法を適用し,従来のスピネル型フェライトに比べ,より高周波帯域で使用可能な六方晶Y型Baフェライト(Ba_2M_2Fe_<12>O_<22>)をガラスマトリックス中へ析出させる条件を新規に確立することを目的とした.主な結果を以下に示す.
    12年度は,主として溶融-急冷法により作製した各種組成のガラスマトリックスの結晶化条件を詳細に検討し,希塩酸によってガラスマトリックスを除去することにより,自形を有したY型Baフェライト(Ba_2Me_2Fe_<12>O_<22>)微粒子を取り出すことが可能であることを明らかにした.13年度には,Y型Baフェライトの析出機構の詳細な検討を行い,Y型Baフェライトは低温で生成するM型Baフェライトを核として析出することを見い出した.14年度には,Me=Zn, Co系でのY型Baフェライト固溶体(Ba_2Zn_<(2-X)>Co_XFe_<12>O_<22>)の合成を試み,X=0〜2の全ての組成範囲で目的とする固溶体が得られることを明らかにした.これらのY型Baフェライト固溶体粉末の電波吸収特性の測定からは,約8〜9GHzの高周波帯域での吸収が確認され,置換量Xの変化によって連続的に吸収周波数がシフトすることを明らかにした.

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  • 交換結合を利用したヘマタイト-イルメナイト系磁性半導体薄膜のスピン電子伝導制御

    研究課題/領域番号:11650697  1999年 - 2001年

    日本学術振興会  科学研究費助成事業  基盤研究(C)

    藤井 達生, 中西 真, 高田 潤

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    配分額:3500000円 ( 直接経費:3500000円 )

    次世代のエレクトロニクス材料(スピントロニクス材料)として期待されている磁性半導体について,磁性半導体のスピン伝導を精密に制御する新規な手法を提案し,実現することを目標に研究を実施した。そこでまず,室温で高いスピン偏極をもつ磁性半導体として酸化物に注目し,新規な酸化物磁性半導体としてヘマタイト-イルメナイト固溶体薄膜の可能性を検討した。ヘマタイト-イルメナイト固溶体には,秩序無秩序転移やFe^<2+>/Fe^<3+>の混合原子価状態など制御すべき因子が多く,優れた磁性半導体特性を示す固溶体薄膜を再現性良く得ることは非常に困難であった。しかし,ヘリコンスパッタ法により成膜時の酸素分圧および基板温度を厳密に制御することで,固溶体薄膜が再現性良く成長する条件を見出し,室温での磁気抵抗効果など磁性半導体としての特徴的な物性をはじめて観測することに成功した。さらに,反強磁性体であるエピタキシャルヘマタイト薄膜が特異的に持りスピンフリップ転移を利用し,強磁性体の磁気構造を制御することを試みた。すなわちヘマタイトを反強磁性体層とする反強磁性体/強磁性体の二層膜を作製し,スピンフリップ転移に伴う磁気構造変化をメスバウアー分光法等で解析した。その結果,二層膜ではスピンフリップ転移が消失することを示し,酸化物磁性体間においても,反強磁性体/強磁性体間に強い交換結合が存在することを初めて明らかにした。残念ながら当初の目標である交換結合を利用した磁性半導体のスピンコントロールは実現できなかったが,鉄系酸化物磁性体の詳細な成膜条件や薄膜の構造や磁性・電子状態など,膨大な基礎的成果を本研究で得ることができた。

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  • 積層磁性膜における磁性層間の磁気相互作用の研究

    研究課題/領域番号:10650691  1998年 - 1999年

    日本学術振興会  科学研究費助成事業  基盤研究(C)

    河本 修, 藤井 達生

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    配分額:1100000円 ( 直接経費:1100000円 )

    1.単層Ni膜:
    膜厚100nmと300nmのNi膜を作成し,飽和磁化,保磁力,垂直異方性,残留磁化比等の磁気特性のAr圧依存性を明らかにした.
    2.O_2を含むAr雰囲気中で作成したNi-O膜:
    (1)O_2分圧を変化させると,O_2/(Ar+O_2)=9%という値を境にして,生成される膜の結晶構造はNiからNiOに変化し,単相であった.(2)格子定数はバルクの値と比べて,Niで0.3%,NiOで0.5%大きかった.(3)Niの飽和磁化はバルクの90%であり,NiOの磁化率は成膜中に磁場を印加した方向とそれに直角に方向で異なるという磁場中スパッタ効果がみられたが,平均するとバルクの値にほぼ等しい.(4)Niの保磁力はO_2が0%のとき,容易方向で1.1kA/mで,困難方向で0.9kA/mであるが,O_2分圧の増加に伴い増加する傾向にある.(5)抵抗率はNi膜ではO_2比の増加に伴い僅か増加する傾向にあり,NiO膜ではNiに比べて僅かぼ4桁のみ増加しバルクのNiOより5桁小さく半導体の性質を示した.このNiO膜は化学量論組成ではなく,Ni欠損型のNi_<1-γ>膜が得られたといえる.
    3.2層Ni/NiO膜:
    (1)NiO層の増加に伴い,結合磁界(H_<ex>),保磁力(H_c),磁気抵抗効果(Δp(H//I)/P)は大きくなる.(2)H_<ex>は,Ni層厚を小さくするのに伴い,大きくなる.(3)NiO層が大きくなる程,H_<ex>が生じるNi層厚が大きくなる.(4)H_cは,Ni層厚の減少に伴い増加する傾向にある.(5)Δp(H//I)/P)は,Ni層厚が大きい膜ほど大きい.
    4.4層Ni/Cu/Ni/NiO膜膜:
    結合磁界と保磁力はCu層が厚くなるに伴い増加する傾向にある.

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  • 電磁環境対策用新規SiC-フェライト系ハイブリッド広帯域電波吸収体の創製

    研究課題/領域番号:10450250  1998年 - 1999年

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    高田 潤, 冨井 洋一, 中西 真, 藤井 達生, 山本 恵久

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    配分額:13700000円 ( 直接経費:13700000円 )

    本研究では、平成10年度に同軸管法による電波吸収特性の測定評価技術の確立を行い、次にSiC前駆体のPCSとフェライト(スピネル型)粉末を混合し、成形焼結する材料作製プロセスの検討を行い、二段階熱処理法の最適条件を把握し、焼結体材料の電波吸収特性の作製条件およびPCS量依存性の解明が図られた。平成11年度には、材料作製条件の更なる検討が深められ、酸素圧制御一段熱処理法を見出すとともに、GHz帯域で電波吸収特性を示す新規材料の創製を試みた。得られた結果を要約すると以下の通りである.
    1.電磁波吸収特性の同軸管法による高精度測定・評価技術の確立:ネットーワークアナライザーを用いて同軸管法によって測定した複素透磁率および複素誘電より計算によって吸収量を評価する技術を100MHz〜10GHzの周波数帯域で確立した.
    2.二段熱処理法によるPCSを用いた新規SiC-スピネルフェライト系電磁波吸収体の開発:(1)不融化処理と熱処理を最適化することによって、本系ハイブリッド電磁波吸収焼結体の作製に初めて成功した。(2)不融化温度によって生成相および電波吸収特性が著しく影響されることを明らかにした。(3)本ハイブリッドセラミックス焼結体の電波吸収特性の整合周波数は、PCS量の増加に伴い約2GHzの高周波側にシフトし、最高約2GHzまで高くなることを見出した。この結果は従来のスピネルフェライトのスネークの限界を超える値であり、SiCのハイブリッド化による大きな効果である。
    3.酸素分圧制御一段熱処理によるPCSを用いた新規SiC-スピネルフェライト系電磁波吸収体の開発:酸素分圧を制御した一段階の熱処理によって、PCSの無機化反応と焼結反応を同時進行させ、ハイブリッド電磁波吸収焼結体の作成に初めて成功した。さらに、このハイブリッド焼結体では、試料厚さによって整合周波数が約900MHzと約9GHzの二種類の電磁波吸収特性を示すことを初めて見出した。

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  • Bi系高温超伝導酸化物のLiのインターカレーションと二次電池正極材への応用の試み

    研究課題/領域番号:09875172  1997年 - 1998年

    日本学術振興会  科学研究費助成事業  萌芽的研究

    高田 潤, 武田 保雄, 中西 真, 藤井 達生

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    配分額:1900000円 ( 直接経費:1900000円 )

    Bi系高温超伝導酸化物(Bi-2212相など)は層状構造を有する化合物であり、これまで電極反応によるLiのインターカレーションの可能性が期待されていたが、現在まで殆ど報告例がない。
    本研究は、Bi-2212相へ電気化学的にLiを導入することを試み、得られたBi-2212相の超伝導特性、構造及び酸素量と構成イオンの価数変化を明らかにするとともに、固相反応法によるLi導入の結果と比較検討することにより、Liのインタカレーションの特徴を明らかにし、更にLiディインターカレーションを試みることによって、Bi-2212相がLi二次電池の正極材として応用できる可能性を検討することを目的とした。得られた結果を要約すると以下の通りである。
    1. 電気化学的手法を用いれば、LiをBi-2212相に常温・常圧でインターカレートすることが可能であり、Li量の制御は極めて容易であることを明らかにした。
    2. Liを電気化学的に導入したBi-2212相の超伝導特性Toは、Li量によって大巾に変化することを初めて見い出した。すなわち、少量のLi導入でTcは85Kから93Kまで上昇した後、急激に低下し、X≧0.3(Li_X Bi_2Sr_<1.6> Ca_<1.5> Cu_2O_zの表記に対して)のLi量で非超伝導体となる。
    3. 電気化学的Li導入では固相反応の場合とは全く異なり、酸素量は全く変化せず、Biの平均価数が減少する結果、Cuの平均価数がX≧0.3.で+2.0まで減少し、これがTcの著しい変化の原因であることを明らかにした。
    4.予め導入したLiは電気化学的な逆反応(放電反応)によって、Bi-2212相より放出できる、すなわちディインターカレーションが可能であることを初めて見い出した。このディインターカレーションによって、Bi-2212相の構造、超伝導特性、酸素量とBiとCuの平均価数は可逆的に変化することを明らかにした。
    5. 以上の結果より、Bi-2212相へのLi二次電池の正極材への応用の可能性は極めて高いことを示した。

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  • In situ Raman分光法による酸化鉄薄膜の構造解析とスピン構造

    研究課題/領域番号:09740524  1997年 - 1998年

    日本学術振興会  科学研究費助成事業  奨励研究(A)

    藤井 達生

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    配分額:2100000円 ( 直接経費:2100000円 )

    本研究者は、数年前、α-Al_2O_3単結晶基板上に成長したエピタキシャルα-Fe_2O_3薄膜のスピン構造が、バルク結晶のものと大きく異なっており、温度により膜面内から垂直方向へと興味あるスピンフリップ転移を示すことを見出し、注目された。この原因として、α-Fe_2O_3薄膜の成長過程に由来する格子歪みの発生が考えられる。本研究では成摸時にin situ Raman分光測定を行い、エピタキシャルα-Fe_2O_3薄膜の薄膜成長過程における構造変化を、連続的にとらえることを試みた。しかし、昨年度に引き続きRaman分光装置の光学系の改善を試みたが、膜厚が数原子層程度しかない超薄膜のRamanスペクトルを測定することはできず、薄膜成長初期の構造変化をとらえることには残念ながら成功しなかった。
    またその研究と並行して、活性化反応性蒸着法によりα-Al_2O_3(001)単結晶基板上にFeTiO_3-α-Fe_2O_3固溶体のエピタキシャル薄膜を作製した。基板温度500℃の低温で成膜した薄膜は、FeイオンとTiイオンが陽イオンサイトをランダムに占有したコランダム構造であった。一方、基板温度700℃で成膜したFe_<2-x>Ti_xO_3膜は、x≧0.4の組成範囲でFeイオンとTiイオンが規則的に配列したイルメナイト構造をとった。FeイオンとTiイオンか規則配列した薄膜のみかフェリ磁性を示した、しかしその自発磁化はイオンが完全に規則配列した場合に期待される値の半分以下であった。さらに、固溶体薄膜の比抵抗は、Fe^<2+>-Fe^<3+>イオンの混合原子価状態をとることにより10^<-1>Ωcmまで低下した。よって本系固溶体薄膜は、新しい酸化物磁性半導体薄膜の有力な候補となることを明らかにした。

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  • ナノメータサイズ窒化物粒子分散強化型新規Mo合金単結晶複合材料の作製と物性

    研究課題/領域番号:08455311  1996年 - 1997年

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    高田 潤, 中西 真, 藤井 達生, 平岡 裕

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    配分額:7400000円 ( 直接経費:7400000円 )

    高融点金属の1つであるMo材料は、熱源ヒ-タ、熱処理トレイ、X線管球など耐熱材料として利用されているが、さらに広範囲に用いられるためには高強度化が強く望まれている。
    本研究は、窒化処理によって形成する表面Mo窒化物層での高硬度化と、Mo-Ti合金の優先窒化を利用したMoマトリックス中への微細TiN粒子の分散析出による高強度化を狙ったものである。特に、我々の25年に及ぶ合金の優先酸化・窒化の研究から、従来の窒化温度よりもはるかに低い温度で窒化することによって、ナノスケールの超微細TiN粒子の分散析出した新しいMo系複合材料を基礎的かつ系統的研究に基づいて創製を試みた。その結果幸運にも、従来材料よりも驚異的に高強度な新規Mo系複合材料の開発に成功した。以下に具体的成果を示す。
    純MoとMo-0.5および1.0wt%Ti合金を従来(1300℃以上)より低い1100℃でNH_3ガス窒化し、窒化挙動、硬さ分布、透過電子顕微鏡による微細構造と結晶学的関係を検討した。
    1.試料表面に形成するMo窒化物層の成長機構を明らかにし、その硬さが最高Hv=1800に達することを示した。更に、このMo窒化物表面層は二層構造を呈し、表面近傍でγ-Mo_2N層、その内部にβ-Mo_2N層が形成すること、および各相で異なる双晶が形成されることを初めて明らかにした。特にβ-Mo_2N層では新しいマクロ双晶の生成を見い出した。
    2.Mo-Ti合金ではMo_2N表面層の内側に純Moには認められない高強度な内部窒化層が形成されることを明らかにした。この層において従来材料の最高硬さ(Hv〜500)の約2倍のHv〜1000を示す飛躍的高強度を達成することに初めて成功した。さらに、この内部窒化層では厚さ約0.45nm(TiNの1ユニット長)、巾2〜4nmの超微細TiN粒子がMoマトリックスと一定の結晶方位関係を有し析出分散することを世界で初めて見い出し、この粒子の超微細分散が著しい強度増加をもたらしたことを明らかにした。

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  • 酸化物人工格子の作製と磁気・光学的性質

    研究課題/領域番号:05453079  1993年 - 1994年

    日本学術振興会  科学研究費助成事業  一般研究(B)

    三浦 嘉也, 藤井 達生, 尾坂 明義

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    配分額:7100000円 ( 直接経費:7100000円 )

    多元活性化反応蒸着でFe_3O_4/MO(M=Mg,Co)酸化物人工格子の作製を試み、MgO(001)基板上には(001)配向を、またα-Al_2O_3(0001)基板上には(111)配向を示す結晶性に優れたFe_3O_4/MO人工格子を作製できた。XRD及びTEMの結果、得られた薄膜は設計通りスピネル型格子と岩塩型格子が交互に積層した人工格子となっていることが確認された。
    強磁性Fe_3O_4層と非磁性MgO層を組み合わせたFe_3O_4/MO人工格子の場合、MgO層はFe_3O_4層間の磁気交換相互作用を遮断し、その保磁力を減少させた。一方、Fe_3O_4層と反強磁性CoO層を組み合わせたFe_3O_4/CoO人工格子の場合、CoO層を介在したFe_3O_4層間の磁気交換相互作用の存在と、Coイオンの持つ1イオン異方性のため保磁力は増加した。また、Fe_3O_4/CoO界面での格子のミスフィットによる磁歪の影響で(100)配向膜では面内方向の、(111)配向膜では積層方向の磁気異方性が生じた。
    Fe_3O_4/MO界面の拡散の程度は、蒸着時の基板温度に大きく依存しており、基板温度の上昇とともに急激に増加した。Fe_3O_4/MO界面において、拡散によりFe_3O_4強磁性層が時期的に希釈され、MFe_3O_4拡散層が形成されると仮定すると、基板温度300℃における拡散層の厚さは約30Åとなり、飽和磁化ならびにメスバウアースペクトルの変化をうまく説明することができた。
    一方、α-Al_2O_3(0001)基板上に酸素分圧を制御することによってTiO_2またはTi_2O_3のエピタキシャル膜を作製することができた。Ti_2O_3は400Kで電気抵抗に急変が現れ金属・半導体転移を示した。

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  • スパッタ法による歪み酸化鉄薄膜の磁気光学特性

    研究課題/領域番号:05855130  1993年

    日本学術振興会  科学研究費助成事業  奨励研究(A)

    藤井 達生

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    配分額:1200000円 ( 直接経費:1200000円 )

    rfマグネトロンスパッタ法を用い、サファイア(alpha-Al_2O_3)単結晶基板上に酸化鉄(alpha-Fe_2O_3)薄膜を作製した。酸化鉄(alpha-Fe_2O_3)は約250Kにモ-リン転移と呼ばれるスピン相転移を持ち、その前後でスピン軸がc面内からc軸方向へと90°変化することが知られている。しかし、単結晶基板上に成長した酸化鉄薄膜の場合は、基板界面におけるミスフィットが結晶格子に歪みを与える結果、スピン相転移はそのスピン軸、転移温度ともバルクに比べ、異なった振舞を示すことが期待される。
    alpha-Al_2O_3(102)単結晶基板上にエピタキシャル成長したalpha-Fe_2O_3(102)について、メスバウアー分光測定を行なった結果、スピン転移温度は400Kへと大きく上昇しており、しかもスピン軸はc軸から<102>方向へと変化していた。そこで4軸回折計による薄膜のX線構造解析を試みた結果、a軸長は約0.5%減少し、一方、c軸長は約0.2%増加していた。一方、alpha-Al_2O_3(001)単結晶基板上にエピタキシャル成長したalpha-Fe_2O_3(001)について、メスバウアー分光測定及びX線構造解析を行なった結果、スピン相転移は極低温(2K)に至まで観測されず、逆にa軸長が約0.3%増加し、c軸長が約0.5%減少していた。従って、得られた酸化鉄薄膜のスピン相転移の変化は、異方的な歪みが原因で生じたものと推論できる。得られた薄膜の磁気光学特性については、現在まだ検討中である。

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  • 高イオン伝導性薄膜のナノサイズ電池用電解質への応用

    研究課題/領域番号:04650705  1992年 - 1993年

    日本学術振興会  科学研究費助成事業  一般研究(C)

    尾坂 明義, 藤井 達生, 難波 徳郎

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    配分額:1870000円 ( 直接経費:1870000円 )

    微小全固体式電池系電解質および光メモリへ材料開発の基礎研究として,(1)F-O-Si-Pb系および(2)CuI-MoO_4-P_2O_5系アモルファス薄膜を作成し,微細構造,伝導性およびレーザー照射による相変化とに関し検討した。
    1.F-O-Si-Pb系アモルファス薄膜
    RFスパッタ装置により放電ガス圧;0.06〜0.07Torr,スパッタ時間;45分の条件でアモルファス膜を作製した。本系アモルファス膜のXPSスペクトルより,Fイオンの濃度は深さ方向に対して一様であったが,比Si-F/Pb-Fは膜表面から内部に向かってわずかに減少しており,Si-O-Si→Si-O^-+F-Si反応による非架橋酸素の増加に帰着できた。3mW He-Neレーザー(λ=632.8nm)を1/500秒照射すると,全ての膜で11μm径の領域でα-SiO_2の結晶化が見られ,所期の高伝導相PbF_2は析出しなかった。一方,Arrheniusの式に従うイオン伝導性を示し,500Kでの伝導率は1.1x10^<-5>S/cmでバルクガラスの約2桁倍であり,活性化エネルギーは106.5kj/molであった。
    2.CuI-MoO_4-P_2O_5系アモルファス薄膜
    高Cuイオン伝導性を有する本系ガラス組成25CuI・25Cu_20・25MoO_4・25Cu_3(PO_4)_3のターゲットを,Arガス圧0.01Torr・rf出力100Wでスパッタリングして得られたアモルファス薄膜は,きめの粗い微粒子構造で,550K以下では伝導率は10^<-8>S/cm程度でほぼ絶縁体であった。また,rf出力を上げるに従いγ-CuIの立方体粒子が発達してきたが,膜中ではCuは2価イオンとして存在している。100Wでスパッタリングした膜をHe-Neレーザー(3mW)で照射すると,F-O-Si-Pb系と異なり1/500秒ですでに8μm径の穿孔が見られ,1秒の照射では12μm径となったが,いずれの場合も結晶相の析出は見られなかった。

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