研究者詳細 - 芳野　極

論文 - 芳野　極

分割表示 162 件中 81 - 100 件目／全件表示 >>

High-pressure phase transitions in FeCr2O4 and structure analysis of new post-spinel FeCr2O4 and Fe2Cr2O5 phases with meteoritical and petrological implications 査読

Takayuki Ishii, Hiroshi Kojitani, Shoichi Tsukamoto, Kiyoshi Fujino, Daisuke Mori, Yoshiyuki Inaguma, Noriyoshi Tsujino, Takashi Yoshino, Daisuke Yamazaki, Yuji Higo, Kenichi Funakoshi, Masaki Akaogi

AMERICAN MINERALOGIST 99 ( 8-9 ) 1788 - 1797 2014年8月

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

We determined phase relations in FeCr2O4 at 12-28 GPa and 800-1600 degrees C using a multi-anvil apparatus. At 12-16 GPa, FeCr2O4 spinel (chromite) first dissociates into two phases: a new Fe2Cr2O5 phase + Cr2O3 with the corundum structure. At 17-18 GPa, the two phases combine into CaFe2O4-type and CaTi2O4-type FeCr2O4 below and above 1300 degrees C, respectively. Structure refinements using synchrotron X-ray powder diffraction data confirmed the CaTi2O4-structured FeCr2O4 (Cmcm), and indicated that the Fe2Cr2O5 phase is isostructural to a modified ludwigite-type Mg2Al2O5 (Pbam). In situ high-pressure high-temperature X-ray diffraction experiments showed that CaFe2O4-type FeCr2O4 is unquenchable and is converted into another FeCr2O4 phase on decompression. Structural analysis based on synchrotron X-ray powder diffraction data with transmission electron microscopic observation clarified that the recovered FeCr2O4 phase has a new structure related to CaFe2O4-type. The high-pressure phase relations in FeCr2O4 reveal that natural FeCr2O4-rich phases of CaFe2O4- and CaTi2O4-type structures found in the shocked Suizhou meteorite were formed above about 18 GPa at temperature below and above 1300 degrees C, respectively. The phase relations also suggest that the natural chromitites in the Luobusa ophiolite previously interpreted as formed in the deep-mantle were formed at pressure below 12-16 GPa.

DOI： 10.2138/am.2014.4736

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

Measurement of thermal conductivity of omphacite, jadeite, and diopside up to 14 GPa and 1000 K: Implication for the role of eclogite in subduction slab 査読

Chao Wang, Akira Yoneda, Masahiro Osako, Eiji Ito, Takashi Yoshino, Zhenmin Jin

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 119 ( 8 ) 6277 - 6287 2014年8月

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 GEOPHYSICAL UNION

Thermal conductivity and diffusivity for three pyroxenes, omphacite, jadeite, and diopside, were determined up to 14 GPa and 1000 K in the Kawai-type multianvil apparatus via the pulse heating method. Measurements for omphacite are characterized by much lower thermal conductivity and thermal diffusivity than those of its two end-members of jadeite and diopside, presumably because of the complex substitution of four cations (Na+1, Ca+2, Al+3, and Mg+2) in omphacite. Therefore, simple arithmetic averaging is unsuitable for estimating thermal conductivity and diffusivity of the jadeite-diopside solid solution system. The thermal property of eclogite was estimated from those of garnet and omphacite. The thermal conductivity of eclogite is much smaller than that of harzburgite, which is assumed to compose of 80% olivine and 20% enstatite, implying that subducted oceanic crust impedes thermal conduction from the hotter wedge mantle to the subducting slab. Thermal structure simulation results show that temperature of the subduction zone is about 50 degrees C decreased when the effect of oceanic crust is included.

DOI： 10.1002/2014JB011208

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

Growth of ringwoodite reaction rims from MgSiO3 perovskite and periclase at 22.5 GPa and 1,800 degrees C 査読

Akira Shimojuku, Asmaa Boujibar, Daisuke Yamazaki, Takashi Yoshino, Naotaka Tomioka, Junshan Xu

PHYSICS AND CHEMISTRY OF MINERALS 41 ( 7 ) 555 - 567 2014年7月

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

The growth rate of ringwoodite reaction rims between MgSiO3 perovskite and periclase was investigated at 22.5 GPa and 1,800 A degrees C for 1-24 h using the Kawai-type high-pressure apparatus. The reaction was likely to proceed by a diffusion-controlled mechanism in which the dominant diffusion mechanism was grain-boundary diffusion. The reaction constant (the width of the ringwoodite reaction rim squared divided by time) determined from these experiments was between 1.3 x 10(-15) and 5.6 x 10(-15) m(2)/s. A Pt inert marker experiment indicated that the MgO component migrated faster than the SiO2 component in ringwoodite. Thus, either Mg or O having the slower diffusion rate controlled the reaction. Because previous diffusion studies have shown that diffusion rates of O are slower than those of Mg, O would be a rate-controlling element for ringwoodite formation from MgSiO3 perovskite and periclase. The growth rate appeared to be too fast to explain the observed topographic rise (similar to 10 km) inside mantle plumes at the 660-km discontinuity.

DOI： 10.1007/s00269-014-0669-x

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

The effect of water on the electrical conductivity of olivine aggregates and its implications for the electrical structure in the upper mantle (vol 288, pg 291, 2009) 査読

Takashi Yoshino, Takuya Matsuzaki, Anton Shatzkiy, Tomoo Katsura

EARTH AND PLANETARY SCIENCE LETTERS 391 135 - 136 2014年4月

Electrical conductivity of brine-bearing quartzite at 1 GPa: implications for fluid content and salinity of the crust 査読

Akira Shimojuku, Takashi Yoshino, Daisuke Yamazaki

EARTH PLANETS AND SPACE 66 ( 1 ) 2014年4月

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 HEIDELBERG

The electrical conductivity of brine-bearing quartzite with fluid fractions of 0.19 to 0.30 and salinity of 3 to 17 wt.% was measured at 800 to 1,100 K and 1 GPa. The conductivity of the brine-bearing quartzite increases with salinity and fluid fraction, but is almost independent of temperature. Our results suggest that regions of high conductivity (10(-3) to 10(-2) S/m) in the crust could be explained by the presence of quartzite with fluids of salinity similar to that of seawater. To account for those regions with the highest conductivity of 10(-1) S/m, quartzite with fluid of high salinity (>10 wt.%) is required.

DOI： 10.1186/1880-5981-66-2

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

Experimental determination of carbon isotope fractionation between graphite and carbonated silicate melt under upper mantle conditions 査読

Shogo Mizutani, M. Satish-Kumar, Takashi Yoshino

EARTH AND PLANETARY SCIENCE LETTERS 392 86 - 93 2014年4月

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 SCIENCE BV

Carbon isotope fractionation between graphite and carbonated silicate melt was determined at 5 GPa and in the temperature range between 1400 and 1900 degrees C. High pressure experiments were carried out in the carbon-saturated model harzbergite system (Enstatite-Magnesite-Olivine-Graphite), where carbonated silicate melt and graphite were the two stable carbon-bearing phases in the run products. Carbonated silicate melting resulted in an isotopic fractionation between graphite and carbon in the silicate melt, where the carbon in the melt is C-13 enriched than co-existing graphite. 13C enrichment in carbonate melt when compared to graphite was further confirmed in experiments where redox melting between olivine and graphite produced carbonate melt as well as carbonate reduction experiments to form graphite. Although a quantitative estimate of fractionation between carbonate melt and graphite could not be obtained, our results indicate that mantle melting in the presence of graphite can result in progressive C-13 carbon isotope enrichment in carbonate melt and depletion in graphite, which can be an alternate explanation for the carbon isotopic heterogeneity observed in the mantle derived carbon. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2014.02.006

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

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

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.

DOI： 10.1007/s10751-014-1014-y

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

High pressure study of transition metal monoxides MnO and CoO: Structure and electrical resistance 査読

E. Ito, D. Yamazaki, T. Yoshino, S. Shan, X. Guo, N. Tsujimo, T. Kunimoto, Y. Higo, K. Funakoshi

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 228 170 - 175 2014年3月

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 SCIENCE BV

We examined the structure of MnO and CoO up to 72 and 88 GPa, respectively, at room temperature by means of in situ X-ray diffraction using the synchrotron radiation at SPring-8. Compression was carried out with the Kawai-type apparatus equipped with sintered diamond anvils. In both MnO and CoO, the cubic B1 lattice starts distorting to the rhombohedral system at 37 and 40 GPa, respectively, which progressively proceeds under increasing pressure. Crystallographic direction of the distortion is opposite; i.e., a contraction along the diagonal [1 1 1] direction of the B1 lattice in MnO and a stretch in CoO. The rhombohedral distortion in 3d transition metal monoxides is discussed. Simultaneously measured electrical resistance of CoO showed characteristic change with pressure; i.e., the pronounced minimum at 14.9 GPa and the maximum at 49 GPa, which serve as good pressure fixed points. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2013.12.009

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

Over 1 Mbar generation in the Kawai-type multianvil apparatus and its application to compression of (Mg0.92Fe0.08)SiO3 perovskite and stishovite 査読

D. Yamazaki, E. Ito, T. Yoshino, N. Tsujino, A. Yoneda, X. Guo, F. Xu, Y. Higo, K. Funakoshi

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 228 262 - 267 2014年3月

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 SCIENCE BV

We generated pressures up to 109.3 GPa in a Kawai-type multianvil apparatus (KMA) equipped with sintered diamond anvils by means of in situ X-ray observation with synchrotron radiation. The unit cell parameters of (Mg0.92Fe0.08)SiO3 perovskite, SiO2 stishovite, and the CaCl2-type polymorph of SiO2 were measured as functions of pressure. We determined the isothermal bulk modulus, K-T0, and its pressure derivative, K'(0), at zero pressure, to be 268 (3) GPa and 3.8 (0.1), respectively, for (Mg0.92Fe0.08)SiO3 Perovskite. Stishovite transforms to the CaCl2-type phase at approximately 54 GPa at 300 K. Compression through stishovite and the CaCl2-type phase can be represented by a single compression curve with K-T0 = 299 (4) GPa and K'(0) = 4.6(0.2). (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2014.01.013

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

Pressure- induced enhancement of proton conduction in brucite 査読

Xinzhuan Guo, Takashi Yoshino

GEOPHYSICAL RESEARCH LETTERS 41 ( 3 ) 813 - 819 2014年2月

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 GEOPHYSICAL UNION

The electrical conductivity of single-crystal brucite was measured as a function of pressure and temperature (P-T) using impedance spectroscopy (IS). IS measurements demonstrated that electrical conductivity perpendicular to the c axis is nearly half order of magnitude higher than that parallel to the c axis under the same P-T conditions. Electrical conductivity increased by 2 orders of magnitude during compression from 3.7 to 11GPa, irrespective of crystallographic direction. However, the conductivity increase with pressure became less significant upon further compression from 11 to 13GPa. The pressure effect is closely related to the interactions between neighboring hydroxyls. The ratio of free protons to total hydrogen increases from 2% to 33% when pressure increases from 3.7 to 13GPa at 950K. This indicates that most of the protons are bound within the crystal structure at low pressures, whereas more protons become free and mobile at higher pressures.
Key Points
<list list-type="bulleted" id="grl51358-list-0001"> <list-item id="grl51358-li-0001">Electrical conductivity of brucite is measured under high P-T conditions <list-item id="grl51358-li-0002">Electrical conductivity of brucite is greatly enhanced by compression <list-item id="grl51358-li-0003">More protons become mobile at higher pressure

DOI： 10.1002/2013GL058627

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

Electrical conductivity of stishovite as a function of water content 査読

Takashi Yoshino, Akira Shimojuku, Danyang Li

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 227 48 - 54 2014年2月

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 SCIENCE BV

The electrical conductivity of stishovite with various Al2O3 and H2O contents was measured at 12 GPa of pressure (P) and temperatures (T) up to 1900 K in a Kawai-type multi-anvil apparatus. Starting materials were pre-synthesized at 12 GPa and 1673 K from various mixtures of SiO2, Al2O3 and Al(OH)(3). The synthesized stishovite aggregates contained various H2O concentrations up to 0.25 wt.%. The conductivity of relatively dry stishovite was almost constant independently of Al content, whereas the conductivity significantly increased with increasing H2O content in stishovite. All electrical conductivity data fit the formula for electrical conductivity sigma = sigma C-0(W) exp{-[Delta H-0 - alpha C-W(1/3)]/kT}, where sigma(0) is the pre-exponential term, C-W is the H2O concentration, Delta H-0 is the activation enthalpy at very low H2O concentration, and k is the Boltzmann constant. The activation enthalpy decreased from 1.22 to 0.90 eV with increasing H2O content from 0.01 to 0.22 wt.%. A nearly linear correlation of the conductivity values on the H2O content suggests that the dominant mechanism of charge transport in stishovite is proton conduction. Although electrical conductivity of hydrous stishovite is higher than that of garnet in the subducted oceanic crust, small amount of hydrous stishovite is insufficient to raise conductivity. On the other hand, hydrous stishovite can contribute to the high conductivity occasionally observed at the mantle transition zone, if the subducted Archean continental crusts with tonalite-trondhjemite-granodiorite (TTG) composition were accumulated above the 660 km seismic discontinuity. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2013.12.003

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

Effects of pressure and temperature on the silicon diffusivity of pyrope-rich garnet 査読

Akira Shimojuku, Tomoaki Kubo, Takumi Kato, Takashi Yoshino, Masayuki Nishi, Tomoki Nakamura, Ryuji Okazaki, Yuki Kakazu

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 226 28 - 38 2014年1月

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 SCIENCE BV

We have determined the pressure and temperature dependencies of Si volume diffusion rates in a single crystal of Pyp(75)Alm(15)Gr(10) garnet at 6-25 GPa and 1400-1800 degrees C by the Si-29 tracer diffusion method. High-pressure experiments were conducted using the Kawai-type multi-anvil high-pressure apparatus. Diffusion profiles were obtained using secondary ion mass spectrometry in the depth-profiling mode. The Si diffusion coefficient in garnet (D-gt) is expressed by the Arrhenius equation: D-gt = D-0 exp(-(E* +- PV*)/RT), with log(10)D(0) = -7.1 +/- 1.7 m(2)/s, E* = 345 +/- 56 kJ/mol, and V* = 4.7 +/- 0.5 cm(3)/mol. Si diffusion seems to be the slowest in the major constituent elements in a pyrope-rich garnet and control rates of plastic deformation. The comparison between Si diffusion rates in garnet and wadsleyite/ringwoodite suggests that garnet has similar or slightly lower strength (at most similar to 2 times) compared with wadsleyite, and has similar or slightly higher strength (at most similar to 3 times) compared with ringwoodite at temperatures ranging from 900 to 1300 degrees C. Thus, strength contrast between subducted oceanic crust and underlying peridotite layer may be small at the mantle transition zone conditions. This result suggests that the separation of subducted oceanic crust from an underlying peridotite layer may not occur. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2013.11.002

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

Crossroads in Earth and Planetary Materials: H-D interdiffusion in brucite at pressures up to 15 GPa 査読

Xinzhuan Guo, Takashi Yoshino, Takuo Okuchi, Naotaka Tomioka

American Mineralogist 98 ( 11-12 ) 1919 - 1929 2013年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

Proton diffusion in brucite was investigated by conducting hydrogen-deuterium (H-D) exchange experiments using multi-anvil high-pressure apparatuses at pressures from 3 to 15 GPa and temperatures in the range of 750-1050 K. The diffusion couple was composed of a natural proton-dominated brucite single crystal surrounded by synthesized D-doped brucite polycrystals. Micro-Raman spectroscopy was used to determine the diffusion profiles of the samples. The D/H diffusion profile across the boundary between single crystal and polycrystalline D-doped brucite showed an asymmetric pattern characterized by faster diffusion in aggregates. The D/H interdiffusion rate determined from the analysis of the single crystal side indicates that the interdiffusion rate increases with increasing H/D ratio. The H-D interdiffusion rate in the direction perpendicular to the c-axis is about 0.5 orders of magnitude higher than that in the direction parallel to the c-axis. At 3 GPa, the H-D interdiffusion coefficients [D(m2/s)] along and perpendicular to the c-axis of brucite at compositions of CnormOD = 0.2 in the single-crystal region were determined to be 3.30(±1.77) × 10 -11exp[-48.2(±5.8) (kJ/mol)/RT] and 1.43(±1.33) × 10-9exp[-67.5(±23.2) (kJ/mol)/RT], respectively. The H-D interdiffusion rate perpendicular to and along the c-axis increased about one order of magnitude by compression from 3 to 10 GPa, but the pressure enhancement became weaker above 10 GPa. From 10 to 15 GPa, there is almost no pressure dependence of proton diffusion for both directions. As pressure increases up to 10 GPa, enhancement of the proton migration is strongly correlated with the activation of the atomic interaction and decrease of O· · ·O' distance induced by compression. The positive pressure effect on the proton diffusion in brucite suggests that proton diffusion in higher-pressure hydrous phase becomes faster because of the shorter O· · ·O' distance.

DOI： 10.2138/am.2013.4550

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

P-V-T relations of gamma-Ca-3(PO4)(2) tuite determined by in situ X-ray diffraction in a large-volume high-pressure apparatus 査読

Shuangmeng Zhai, Daisuke Yamazaki, Weihong Xue, Lijin Ye, Chaowen Xu, Shuangming Shan, Eiji Ito, Akira Yoneda, Takashi Yoshino, Xinzhuan Guo, Akira Shimojuku, Noriyoshi Tsujino, Ken-Ichi Funakoshi

AMERICAN MINERALOGIST 98 ( 10 ) 1811 - 1816 2013年10月

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

Tuite, gamma-Ca-3(PO4)(2), is regarded as an important phosphate mineral in the deep mantle playing a crucial role as a host for rare earth elements, large ion lithophile elements, and phosphorus. In this study we report the thermoelastic properties of synthetic gamma-Ca-3(PO4)2 at simultaneously high pressures and temperatures of up to 35.4 GPa and 1300 K, respectively, as determined by means of in situ energy-dispersive X-ray diffraction in a large-volume multi-anvil apparatus. The pressure-volume-temperature data obtained for gamma-Ca-3(PO4)(2) were fitted by the high-temperature Birch-Murnaghan equation of state to yield V-0 = 447.4(4) angstrom(3), K-T0 = 100.8(18) GPa, K-T0' = 5.74(13), (partial derivative K-T/partial derivative T)(p) = -0.020(1) GPa/K, and alpha(T) = 3.26(18) x 10(-5) + 1.76(24) x 10(-8) T. In addition, fitting the present data to the Mie-Gruneisen-Debye equation of state gives gamma(0) = 1.35(6), Theta(0) = 944(136) K, and q = 0.37(29). Based on the thermoelastic properties obtained in our study, the density profiles of gamma-Ca-3(PO4)(2) tuite along typical cold and hot slab geotherms were calculated and are compared with those of the coexisting silicate minerals in subducting mid-ocean ridge basalt.

DOI： 10.2138/am.2013.4403

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

Electrical conductivity of dense hydrous magnesium silicates with implication for conductivity in the stagnant slab 査読

Xinzhuan Guo, Takashi Yoshino

EARTH AND PLANETARY SCIENCE LETTERS 369 239 - 247 2013年5月

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 SCIENCE BV

Electrical conductivities of dense hydrous magnesium silicates (DHMS), phase A, super-hydrous phase B (SuB) and phase D, were measured by means of impedance spectroscopy in the frequency range of 10(-1)-10(6) Hz at temperatures up to 775, 700 and 700 K and pressures of 10, 18 and 22 GPa, respectively. For all phases, the increase in electrical conductivity (sigma) with temperature follows the Arrhenian formula: sigma = sigma(0)exp(-(Delta H/kT)). The pre-exponential factors (sigma(0)) and activation enthalpies (Delta H) of phase A, SuB and phase D yield values of 7.28 +/- 0.82 S/m and 0.77 +/- 0.01 eV, 292 +/- 48 S/m and 0.83 +/- 0.01 eV and 1342 +/- 154 and 0.75 +/- 0.01 eV, respectively. Higher pressure DHMS phases show higher conductivity values. The electrical conductivities of phase D and super hydrous phase B are about two and one orders of magnitude higher than that of phase A in the same temperature range, respectively. Although the proton conduction is considered to be a dominant mechanism, there is no clear relationship between water content and conductivity. Rather the conductivity of DHMS phase is closely related to the O center dot center dot center dot O distance. The conductivity-depth profiles for a cold subduction zone were constructed based on the phase proportion predicted in the descending slab. The results show distinctly lower conductivity values than those geophysically observed beneath the northeastern China and the Philippine Sea, where the cold slab stagnates in the mantle transition zone. Consequently, the DHMS phases themselves cannot be a main contributor to enhance the conductivity in the stagnant slab. Dehydration of the stagnant slab would strongly enhance the conductivities in the transition zone beneath northeastern China and Philippine Sea. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2013.03.026

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

Reply to the comment on: Carbon isotope fractionation in the Fe-C system at HPHT experiments by Reutsky and Borzdov 査読

Madhusoodhan Satish-Kumar, Takashi Yoshino, Hayato So, Mutsumi Kato, Yoshikuni Hiroi

EARTH AND PLANETARY SCIENCE LETTERS 368 222 - 224 2013年4月

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

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

記述言語：英語掲載種別：研究論文（学術雑誌）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

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

High-pressure X-ray diffraction study and thermoelectric measurements of Mg2Si 査読

Y. Mori, Y. Kaihara, S. Nakamura, T. Yoshino, K. Takarabe

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 10, NO 12 10 ( 12 ) 1847 - 1849 2013年

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：WILEY-V C H VERLAG GMBH

Magnesium silicide (Mg2Si) is a promising as an environmental friendly thermoelectric material. It is difficult to synthesize high-purity Mg2Si because of the boiling of Mg and the oxidation of Mg. In order to avoid the disagreement of stoichiometric ratio and the oxidation, we have performed high-pressure synthesis. And also the high-pressure X-ray diffraction by the synchrotron radiation source was carried out to find synthetic condition under pressure, and we have found that Mg2Si was synthesized at 1.0 GPa beyond 573 K. Because high synthetic temperature causes the oxidation of Mg, the high-pressure synthesis by means of a piston cylinder apparatus performed at 673 K. The synthesized compounds were evaluated by XRD analysis and thermoelectric measurement. Because the size of compounds synthesized under pressure is small, we also developed and evaluated the new equipment of the thermoelectric measurement for such as small sample. (c) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

DOI： 10.1002/pssc.201300404

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

Electrical Conductivity of Mantle Minerals: Role of Water in Conductivity Anomalies 査読

Takashi Yoshino, Tomoo Katsura

ANNUAL REVIEW OF EARTH AND PLANETARY SCIENCES, VOL 41 41 605 - + 2013年

記述言語：英語掲載種別：論文集(書籍)内論文出版者・発行元：ANNUAL REVIEWS

The electrical conductivity of Earth's mantle has recently become an interesting topic across diverse Earth science communities. Many electrical conductivity data of mantle phases have been accumulated through the development of high-pressure experiments. These data will provide information on valence states, water concentration, Fe concentration, oxygen fugacity, and the connectivity of the conductive phase in geological materials such as minerals, melts, and rocks. Although several groups have measured the electrical conductivity of mantle materials at high pressure, they have provided inconsistent results, especially with regard to the effect of water. Thus, it is timely to review the problems underlying experimental techniques. We discuss the current understanding of the effect of water on the electrical conductivity of nominally anhydrous mantle minerals, with some speculation on the form of volatile components in Earth's interior. Finally, we consider the role of water in major conductivity anomalies observed in the upper mantle and transition zone.

DOI： 10.1146/annurev-earth-050212-124022

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

Erratum to: Re-evaluation of electrical conductivity of anhydrous and hydrous wadsleyite [Earth Planet. Sci. Lett. 337-338 (1) (2012) 56-67] 査読

Takashi Yoshino, Tomoo Katsura

Earth and Planetary Science Letters 357-358 422 2012年12月

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