研究者詳細 - 芳野　極

論文 - 芳野　極

分割表示 162 件中 121 - 140 件目／全件表示 >>

ELECTRICAL CONDUCTIVITY OF ENSTATITE UP TO 20 GPa AND 1600K 査読

Zhang Bao-Hua, Wu Xiao-Ping, Xu Jun-Shan, Tomoo Katsura, Takashi Yoshino

CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION 53 ( 3 ) 760 - 764 2010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：SCIENCE CHINA PRESS

The electrical conductivity of (Mg(0.9)Fe(0.1)) SiO(3) enstatite has been measured at pressures of 10 similar to 20 GPa and temperatures of 750 similar to 1600 K using a Kawai-type multianvil high-pressure apparatus. The experimental results demonstrate that there are two conduction mechanisms, small polaron is the dominant mechanism in the high temperature regions, while proton is in charge of the low temperature regions as water is determined in the recovered sample in this study. On the other hand, we observe a pressure induced phase transition from enstatite to ringwoodite under pressure of 20 GPa by X-ray diffraction. The conductivity of ringwoodite with water at 20 GPa is in good agreement with the available measurements of hydrous ringwoodite.

DOI： 10.3969/j.issn.0001-5733.2010.03.032

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

Laboratory Electrical Conductivity Measurement of Mantle Minerals 査読

Takashi Yoshino

SURVEYS IN GEOPHYSICS 31 ( 2 ) 163 - 206 2010年3月

記述言語：英語出版者・発行元：SPRINGER

Electrical conductivity structures of the Earth's mantle estimated from the magnetotelluric and geomagnetic deep sounding methods generally show increase of conductivity from 10(-4)-10(-2) to 10(0) S/m with increasing depth to the top of the lower mantle. Although conductivity does not vary significantly in the lower mantle, the possible existence of a highly conductive layer has been proposed at the base of the lower mantle from geophysical modeling. The electrical properties of mantle rocks are controlled by thermodynamic parameters such as pressure, temperature and chemistry of the main constituent minerals. Laboratory electrical conductivity measurements of mantle minerals have been conducted under high pressure and high temperature conditions using solid medium high-pressure apparatus. To distinguish several charge transport mechanisms in mantle minerals, it is necessary to measure the electrical conductivity in a wider temperature range. Although the correspondence of data has not been yet established between each laboratory, an outline tendency of electrical conductivity of the mantle minerals is almost the same. Most of mineral phases forming the Earth's mantle exhibit semiconductive behavior. Dominant conduction mechanism is small polaron conduction (electron hole hopping between ferrous and ferric iron), if these minerals contain iron. The phase transition olivine to high-pressure phases enhances the conductivity due to structural changes. As a result, electrical conductivity increases in order of olivine, wadsleyite and ringwoodite along the adiabat geotherm. The phase transition to post-spinel at the 660 km discontinuity further can enhance the conductivity. In the lower mantle, the conductivity once might decrease in the middle of the lower mantle due to the iron spin transition and then abruptly increase at the condition of the DaEuro(3) layer. The impurities in the mantle minerals strongly control the formation, number and mobility of charge carriers. Hydrogen in nominally anhydrous minerals such as olivine and high-pressure polymorphs can enhance the conductivity by the proton conduction. However, proton conduction has lower activation enthalpy compared with small polaron conduction, a contribution of proton conduction becomes smaller at high temperatures, corresponding to the mantle condition. Rather high iron content in mantle minerals largely enhances the conductivity of the mantle. This review focuses on a compilation of fairly new advances in experimental laboratory work together with their explanation.

DOI： 10.1007/s10712-009-9084-0

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

Electrical conductivity measurements of periclase under high pressure and high temperature 査読

Xiaoping Wu, Baohua Zhang, Junshan Xu, Tomoo Katsura, Shuangmeng Zhai, Takashi Yoshino, Geeth Manthilake, Anton Shatskiy

PHYSICA B-CONDENSED MATTER 405 ( 1 ) 53 - 56 2010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

The electrical conductivity of sintered polycrystalline periclase has been measured at 20GPa and temperatures up to 1700 K with a KAWAI-type multi-anvil apparatus. Arrhenius plot of the electrical conductivity shows two linear regions, implying a change of charge transport mechanism with temperature in this experiment. At temperatures below 700K small polaron conduction dominates, with an activation energy of 0.2 eV. At higher temperatures, the activation energy is determined to be 1.18 eV, which is much higher than 0.2 eV at low temperature. Our observations suggest the high-temperature conduction is attributed to a large polaron process with magnesium vacancy trapping hole on oxygen. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2009.08.036

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

Preliminary reports on in-situ X-ray observation of "post-perovskite" in CaRuO3 査読

D. Yamazaki, E. Ito, T. Yoshino, X-G Guo, S. Shun, M. Nishi, Y. Higo, K. Funakoshi

INTERNATIONAL CONFERENCE ON HIGH PRESSURE SCIENCE AND TECHNOLOGY, JOINT AIRAPT-22 AND HPCJ-50 215 012096 2010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：IOP PUBLISHING LTD

Phase transformation from perovskite to "post-perovskite" and reserve transition in CaRuO3 was observed by in situ X-ray diffraction at pressure of 20-22 GPa and temperature of 1173-1523 K. These pressure and temperature conditions are 1-2 GPa lower than previous results by quenched method. The axial compressibility is estimated to be a/a(0)>b/b(0)>c/c(0). This result is inconsistent with previous result on CaIrO3.

DOI： 10.1088/1742-6596/215/1/012096

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

High pressure generation and investigation of the spin transition of ferropericlase (Mg0.83Fe0.17)O 査読

E. Ito, T. Yoshino, D. Yamazaki, A. S. Shatskiy, S. Shan, X. Guo, T. Katsura, Y. Higo, K. Funakoshi

INTERNATIONAL CONFERENCE ON HIGH PRESSURE SCIENCE AND TECHNOLOGY, JOINT AIRAPT-22 AND HPCJ-50 215 012099 2010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：IOP PUBLISHING LTD

High pressure generation has been tried by using the Kawai-cell equipped with sintered diamond cubes in conjunction with investigation of the spin transition in Fe2+ of (Mg0.83Fe0.17)O (ferropericlase, Fp). The Kawai-cell was squeezed in the DIA type press SPEED mkII installed at SPring-8. The volumes of the Fp and Au pressure standard were simultaneously determined by in situ X-ray diffraction using the synchrotron radiation. The maximum attainable pressure has reached 90 GPa at 300 K based on Anderson et al.'s Au scale [4]. The P-V data of (Mg0.83Fe0.17)O were acquired at 300 K and 700 K up to 90 GPa. From detailed analysis of the compression data, it is suggested that the spin transition proceeds over pressure ranges from 50 to 70 GPa at 300 K and from 50 to 75 GPa at 700 K.

DOI： 10.1088/1742-6596/215/1/012099

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

Electrical conductivity of mantle peridotite at the uppermost lower mantle condition 査読

T. Yoshino, T. Katsura, D. Yamazaki, E. Ito

INTERNATIONAL CONFERENCE ON HIGH PRESSURE SCIENCE AND TECHNOLOGY, JOINT AIRAPT-22 AND HPCJ-50 215 012102 2010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：IOP PUBLISHING LTD

Electrical conductivity of mantle peridotite was measured at 25 GPa and temperature up to 1800 K in a Kawai-type multi-anvil apparatus. The starting material was gel with a composition of fertile spinel lherzolite (KLB1). After the conductivity measurement, mineral phases of run products are composed of magnesium silicate perovskite, ferro-periclase and Ca perovskite. The conductivity value of the peridotite is distinctly higher than those of post-spinel and magnesian silicate perovskite with a composition of (Mg(0.9), Fe(0.1)) SiO(3), but lower than that of ferro-periclase. Both absolute values and change in activation enthalpy for the conductivity of the mantle peridotite are similar to those for the silicate perovskite. A presence of aluminous perovskite with substantial amount of ferric iron in crystal structure would enhance bulk conductivity of the lower mantle.

DOI： 10.1088/1742-6596/215/1/012102

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

Electrical conductivity of the major upper mantle minerals: a review 査読

T. Katsura, T. Yoshino, G. Manthilake, T. Matsuzaki

RUSSIAN GEOLOGY AND GEOPHYSICS 50 ( 12 ) 1139 - 1145 2009年12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 the major upper mantle minerals, namely, olivine, wadsleyite and ringwoodite, is reviewed in this paper. There are mainly three electrical conduction mechanisms for three upper mantle minerals: hopping, ionic and proton conductions. The charge carriers for these conduction mechanisms are an electron hole in Fe ion, a vacancy in Mg site, and a proton, respectively. Hopping conduction is the most essential conduction mechanism for the major upper mantle minerals. Because ionic conduction has high activation energy, it becomes a dominant conduction mechanism only at high temperatures. Proton conduction contributes at relatively low temperatures. If the mantle minerals contain large amount of water (more than 0.1 wt.%), proton conduction can be a dominant conduction mechanism, even at high temperatures. (C) 2009, IGM, Siberian Branch of the RAS. Published by Elsevier B. V. All rights reserved.

DOI： 10.1016/j.rgg.2009.11.012

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 of the upper mantle 査読

Takashi Yoshino, Takuya Matsuzaki, Anton Shatskiy, Tomoo Katsura

EARTH AND PLANETARY SCIENCE LETTERS 288 ( 1-2 ) 291 - 300 2009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：ELSEVIER SCIENCE BV

The electrical conductivity of San Carlos olivine aggregate of various water content was measured at a pressure of 10 GPa in a Kawai-type multi-anvil apparatus. Conductivity measurements were performed on two sets of samples to determine the effect on conductivity of water in olivine: 1) a hydrogen-doped sample and 2) a hydrogen-undoped sample. To minimize water escape from the hydrogen-doped samples, the conductivity measurement was carried out below 1000 K. Three conduction mechanisms were identified from the Arrhenian behavior of the undoped samples, which include a small amount of water. A change in the activation enthalpy indicated that the dominant conduction mechanism changed from proton conduction to small polaron conduction with increasing temperature. At temperatures above 1700 K. the activation enthalpy exceeds 2 eV suggesting that the dominant mechanism of charge transport would be ionic conduction. The conductivity increased with increasing water content. The activation enthalpy for proton conduction tends to decrease slightly with increasing water content. The activation enthalpy determined for each run had similar values (similar to 0.9 eV). Taking the water concentration dependence of activation enthalpy into account for proton conduction, all data were fitted to the electrical conductivity formula (sigma=sigma(01)exp[-E-1/kT]+sigma(OH)exp[-E-H/kT]+sigma(OP)C(W)exp[-(E-0-alpha C-W(1/3))/kT], where sigma(0) represents a pre-exponential term, C-W is the water content in weight percent, E is the activation enthalpy, E-0 is the activation enthalpy for proton conduction at very low water concentration, alpha is the geometrical factor, k is the Boltzmann constant, T is absolute temperature and subscripts 1, H and P denote ionic, hopping (small polaron) and proton conductions, respectively. The conductivity jump at the 410 km discontinuity (olivine-wadsleyite transition) is much smaller than that previously predicted. Since the contribution of proton conduction to the bulk electrical conductivity decreases with increasing temperature the high conductivity anomaly at the top of the asthenosphere cannot be explained by olivine hydration. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2009.09.032

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

P-V-T relations of the MgSiO3 perovskite determined by in situ X-ray diffraction using a large-volume high-pressure apparatus (vol 36, L01305, 2009) 査読

Tomoo Katsura, Sho Yokoshi, Kazuaki Kawabe, Anton Shatskiy, M. A. Geeth, M. Manthilake, Shuangmeng Zhai, Hiroshi Fukui, H. A. Chamathni, I. Hegoda, Takashi Yoshino, Daisuke Yamazaki, Takuya Matsuzaki, Akira Yoneda, Eiji Ito, Mitsuhiro Sugita, Naotaka Tomioka, Kenji Hagiya, Akifumi Nozawa, Ken-ichi Funakoshi

GEOPHYSICAL RESEARCH LETTERS 36 ( 16 ) 2009年8月

Well-wetted olivine grain boundaries in partially molten peridotite in the asthenosphere 査読

Takashi Yoshino, Daisuke Yamazaki, Kenji Mibe

EARTH AND PLANETARY SCIENCE LETTERS 283 ( 1-4 ) 167 - 173 2009年6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

Pore morphology in partially molten peridotites strongly controls many physical properties of the Earth's deep materials. The dihedral angle of the olivine-silicate melt system is a key factor in understanding the physical behavior of the upper mantle. For a limited range of melt compositions, previous studies of wetting behavior have determined dihedral angles of 30-50 degrees. However, the dihedral angle of partially molten peridotites should be variable under a wide range of pressure and temperature conditions, because wetting behavior depends strongly on liquid structure and composition. The dihedral angles of olivine-silicate melt in partially molten peridotite were determined at pressures of 1 to 7 GPa and temperatures between 1473 and 1993 K. The dihedral angle decreased (approaching 0 degrees) with increasing temperature, which corresponds to completely wetted grain boundaries. This angle variation probably depends on a decrease in the solid-melt interfacial energy, which is a product of large change in melt structure. These results suggest that the presence of partial melt would have large influences on the physical properties of the upper mantle even if the melt fraction was very low. if grain boundary diffusion creep dominates in the asthenosphere, the shear strength of partially molten peridotites at asthenospheric pressure (similar to 3 GPa) would be much lower than that predicted from experiments at relatively lower pressure (similar to 0.3 GPa) because of the extremely low grain boundary contiguity. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2009.04.007

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

P-V-T relations of wadsleyite determined by in situ X-ray diffraction in a large-volume high-pressure apparatus 査読

Tomoo Katsura, Anton Shatskiy, M. A. Geeth M. Manthilake, Shuangmeng Zhai, Daisuke Yamazaki, Takuya Matsuzaki, Takashi Yoshino, Akira Yoneda, Eiji Ito, Mitsuhiro Sugita, Natotaka Tomioka, Akifumi Nozawa, Ken-ichi Funakoshi

GEOPHYSICAL RESEARCH LETTERS 36 ( 11 ) L11307 2009年6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 volume of Mg2SiO4 wadsleyite has been precisely measured at pressures of 11 to 20 GPa and temperatures of 300 to 2100 K by means of in situ X-ray diffraction in a multi-anvil apparatus. The fixed isothermal bulk modulus K-T0 = 169.2 GPa gives its pressure derivative K-T0' = 4.1(1). The fixed Debye temperature theta(0) = 814 K gives a Gruneisen parameter at ambient pressure gamma(0) = 1.64(2) and its logarithmic volume dependence q = 1.5(1). The pressure derivative of the isothermal bulk modulus, Anderson-Gruneisen parameter and thermal expansion coefficient at ambient pressure are found to be (partial derivative K-T/partial derivative(T))(P) =-0.021(1) GPa/K, delta(T) = 5.5(2), alpha(0) = 2.31(3) x 10(-5) + 1.18(3) x 10(-8) (T - 300) K-1. The pressure and volume dependence of thermal expansion coefficient of wadsleyite is the smallest among those of the mantle minerals. The adiabatic temperature gradient in the upper part of the mantle transition zone is 0.34(1) K/km. Citation: Katsura, T., et al. (2009), P-V-T relations of wadsleyite determined by in situ X-ray diffraction in a large-volume high-pressure apparatus, Geophys. Res. Lett., 36, L11307, doi:10.1029/2009GL038107.

DOI： 10.1029/2009GL038107

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

Effect of iron content on electrical conductivity of ringwoodite, with implications for electrical structure in the transition zone 査読

Takashi Yoshino, Tomoo Katsura

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 174 ( 1-4 ) 3 - 9 2009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 conductivity of ringwoodite with various iron contents [Fe/Fe + Mg) = 0.09, 0.2 and 0.3] was measured at pressure (20 GPa) and temperature (up to 1900 K) conditions of the lower part of the mantle transition zone in a Kawai-type multi-anvil apparatus. The conductivity increased with increasing total iron content. All electrical conductivity data were fitted to the formula of electrical conductivity sigma = sigma(0) X-Fe exp(-H/kT), where sigma(0) is the pre-exponential term, X-Fe is the mole fraction of iron content in the Mg site, H is the activation enthalpy, k is the Boltzmann constant and T is absolute temperature. The activation enthalpy becomes higher at a certain temperature. At high temperatures, the activation enthalpy decreased from 1.44 to 0.92 eV with increasing total Fe content. At low temperatures less than 1000 K, the activation enthalpy also decreases from 1.15 to 0.74 eV with total Fe content. Dependence of the activation enthalpy on Fe content suggests that the dominant mechanism of charge transport is Fe2+-Fe3+ hopping (small polaron). Recent electrical conductivity-depth profiles of the transition zone beneath the Pacific Ocean obtained from the electromagnetic induction Study shows that the conductivity values between 520 and 660 km depths may be explained by ringwoodite with Fe/Fe + Mg) = 0.10. On the other hand, assuming a normal geotherm, conductivity values beneath the continent or stable craton are considerably lower than those of ringwoodite with Fe/(Fe + Mg) = 0.10. Taking into consideration results from the global seismic tomographic studies, relatively low conductivity in these regions can be explained by the existence of a cooler region compared with the surrounding mantle, rather than the presence of iron-poor ringwoodite, or a combination of both. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2008.09.015

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

Electrical conductivity of wadsleyite as a function of temperature and water content 査読

M. A. G. M. Manthilake, Takuya Matsuzaki, Takashi Yoshino, Shigeru Yamashita, Eiji Ito, Tomoo Katsura

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 174 ( 1-4 ) 10 - 18 2009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 conductivity of wadsleyite was measured at 16 GPa using a KAWAI-type multi-anvil press under controlled oxygen fugacity. Water-doped and -undoped samples were used to examine the effect of water on conductivity. Two water-doped wadsleyite samples used for the conductivity measurements contained 0.3 +/- 0.01 and 1.2 +/- 0.02 wt.% water. The temperature ranges for the conductivity measurements were 500-2000 K for water-undoped samples and 500-1000 K for water-doped samples. Above 1500 K, the electrical conductivity values are essentially the same among different runs with an average activation enthalpy of 1.5 eV, suggesting that small polaron conduction should dominate. Below 1000 K, the conductivity systematically increases with increasing water content, suggesting proton conduction as a dominant conduction mechanism. Electrical conductivity of anhydrous wadsleyite in the mantle transition zone should be about 3 x 10(-2) S/m in the normal geotherm. Hydration enhances the conductivity of wadsleyite; by containing 0.1 wt.% water, the conductivity of wadsleyite increases by 0.3 log units. The conductivity jump associated with the dry olivine-wadsleyite transition is only 0.7 log units. A dry olivine-wadsleyite conductivity model well agrees with the current semi-global conductivity-depth profiles, thus the concept of a globally hydrated mantle transition zone is not necessary in view of electrical conductivity. The high conductivity observed in the wedge mantle cannot be explained by hydrous wadsleyite. Alternatively, the presence of either phase E or supercritical fluids in the wedge mantle is proposed. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2008.06.001

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

Texture of (Mg,Fe)SiO3 perovskite and ferro-periclase aggregate: Implications for rheology of the lower mantle 査読

Daisuke Yamazaki, Takashi Yoshino, Takuya Matsuzaki, Tomoo Katsura, Akira Yoneda

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 174 ( 1-4 ) 138 - 144 2009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

Rheology of the lower mantle characterizes the dynamics of the earth's interior and it is often controlled by the textures of the constituting material which are (Mg,Fe)SiO3 perovskite and ferro-periclase aggregate. We conducted high-pressure experiments to synthesize the (Mg,Fe)SiO3 perovskite and ferro-periclase aggregates and measured two important textures of "grain size" and "dihedral angle". The grain growth rates of perovskite and (ferro-)periclase in two phase aggregates were influenced by the iron content and increased with factors of similar to 1.5 in iron-rich system. This difference in grain growth rates indicates that the viscosity of aggregates of iron-rich system is only a few times greater than that of iron-poor system for likely diffusion creep in the lower mantle. In contrast, the change of the dihedral angle of perovskite - periclase - perovskite at triple grain junction with variation of iron content was not observed systematically, but the dihedral angle decreases from similar to 110 degrees to similar to 105 degrees with an increase of temperature from 1673 to 2273 K. The dihedral angle of 105-110 degrees would imply the interconnected network spatially of ferro-periclase in the aggregates and the connectivity increases with temperature. As a result, at higher temperature, ferro-periclase plays more important role for understanding the rheology of the lower mantle because ferro-periclase is a few order of magnitude softer than (Mg,Fe)SiO3 perovskite. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2008.11.002

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

Reply to Comments on "Electrical conductivity of wadsleyite as a function of temperature and water content" by Manthilake et al. Discussion 査読

Takashi Yoshino, Tomoo Katsura

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 174 ( 1-4 ) 22 - 23 2009年5月

Determination of high-pressure phase equilibria of Fe2O3 using the Kawai-type apparatus equipped with sintered diamond anvils 査読

Eiji Ito, Hiroshi Fukui, Tomoo Katsura, Daisuke Yamazaki, Takashi Yoshino, Yoshitaka Alizawa, Atsushi Kubo, Sho Yokoshi, Kazuyoki Kawabe, Shuangmeng Zhai, Anton Shatzkiy, Maki Okube, Akifumi Nozawa, Ken-Ichi Funakoshi

AMERICAN MINERALOGIST 94 ( 2-3 ) 205 - 209 2009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：MINERALOGICAL SOC AMER

Phase equilibria of Fe2O3 have been studied tip to 58 GPa and 1400 K using the Kawai-type multi anvil apparatus equipped with sintered diamond anvils. Identification of phases and pressure determination has been carried out by means of in situ X-ray observation using synchrotron radiation at SPring-8. Hematite (phase I) successively transforms to the Rh2O3(II)-type structure (phase II) and then to an orthorhombic structure (phase III) with increasing pressure. The transformations of hematite into high-pressure phases have been observed only at temperatures higher than 500 K, which is not concordant with previous results obtained by using the diamond anvil cell. Volume changes accompanied by the I-II and II-III transformations are calculated to be 2.8 and -5.0%, respectively. The phase boundary between I and II phases and that between II and III have been proposed to be P (GPa)- 0.015 T(K) + 44.2 and P (GPa) = -0.005 T(K) + 48.7, respectively. Possible correlation between a Mott transition and the phase stabilities may be concealed at room temperature due to Slow reaction kinetics of the structural transformations.

DOI： 10.2138/am.2009.2913

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

P-V-T relations of MgSiO3 perovskite determined by in situ X-ray diffraction using a large-volume high-pressure apparatus 査読

Tomoo Katsura, Sho Yokoshi, Kazuaki Kawabe, Anton Shatskiy, M. A. Geeth M. Manthilake, Shuangmeng Zhai, Hiroshi Fukui, H. A. Chamathni I. Hegoda, Takashi Yoshino, Daisuke Yamazaki, Takuya Matsuzaki, Akira Yoneda, Eiji Ito, Mitsuhiro Sugita, Naotaka Tomioka, Kenji Hagiya, Akifumi Nozawa, Ken-ichi Funakoshi

GEOPHYSICAL RESEARCH LETTERS 36 ( 1 ) L01305 2009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：AMER GEOPHYSICAL UNION

The volume of MgSiO3 perovskite has been precisely measured at pressures of 19 to 53 GPa and temperatures of 300 to 2300 K by means of in situ X-ray diffraction in a multi-anvil apparatus. The present results indicate the isothermal bulk modulus K-T0 = 256(2) GPa and its pressure derivative K-T0' = 3.8(2). The fixed Debye temperature theta(0) = 1030 K gives a Gruneisen parameter at ambient pressure gamma(0) = 2.6(1) and its logarithmic volume dependence q = 1.7(1). The pressure derivative of the isothermal bulk modulus, Anderson-Gruneisen parameter and thermal expansion coefficient at ambient pressure are found to be (partial derivative K-T/partial derivative T)(P) = -0.035(2) GPa/K, delta(T) = 6.5(5), alpha(0) = 2.6(1) x 10(-5) + 1.0(1) x 10(-8) (T - 300)/K. Thus the thermal expansion coefficient largely becomes smaller with increasing pressure. The adiabatic geotherm would be fairly large, such as 0.41 K/km at a 660 km depth, and becoming smaller with increasing depth. The temperature and adiabatic geothermal gradient at the bottom of the D' layer would be 2400 K and 0.14 K/km. The buoyancy-driven mantle convection could be very small in the lower part of the lower mantle. Citation: Katsura, T., et al. (2009), P-V-T relations of MgSiO3 perovskite determined by in situ X-ray diffraction using a large-volume high-pressure apparatus, Geophys. Res. Lett., 36, L01305, doi: 10.1029/2008GL035658.

DOI： 10.1029/2008GL035658

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

The temperature-pressure-volume equation of state of platinum 査読

Masanori Matsui, Eiji Ito, Tomoo Katsura, Daisuke Yamazaki, Takashi Yoshino, Ayako Yokoyama, Ken-ichi Funakoshi

JOURNAL OF APPLIED PHYSICS 105 ( 1 ) 013505 2009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：AMER INST PHYSICS

High-temperature and high-pressure equations of state (EOSs) of Pt have been developed using measured shock compression data up to 290 GPa and volume thermal expansion data between 100 and nearly 2000 K and 0 GPa. The lattice thermal pressures at high temperatures have been estimated based on the Mie-Gruneisen relation with the Debye thermal model and the Vinet isothermal EOS. The contribution of electronic thermal pressure at high temperatures has also been included here. The optimized EOS parameters of Pt are K-0T = 273 GPa, K'(0T) = 5.20, gamma(0) = 2.70, and q = 1.10 with Theta(0) = 230 K, where the subscript 0 refers to the ambient conditions. The temperature-pressure-volume (T-P-V) data of Pt have also been measured up to 1600 K and 42 GPa, using synchrotron powder x-ray diffraction experiments combined with a Kawai-type multianvil high pressure apparatus and sintered diamond anvils. We find that the newly developed T-P-V EOS of Pt is fully consistent with not only the shock compression data up to 290 GPa and volume thermal expansion data up to near 2000 K, but also the present measured synchrotron T-P-V data and recently measured T-P-V data of Pt up to 1900 K and 80 GPa. Thus we find that there is no need to include a volume dependence of q over a wide pressure range up to more than 300 GPa. The present EOS has been developed without any pressure scale. Such excellent consistency between the EOS and experimental values over wide temperature and pressure ranges shows that the present EOS can be used as a reliable primary pressure standard for static experiments up to 300 GPa and 3000 K. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3054331]

DOI： 10.1063/1.3054331

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

Electrical conductivity of olivine, wadsleyite and ringwoodite 査読

Tomoo Katsura, Takashi Yoshino, Takuya Matsuzaki, Geeth Manthilake

Japanese Magazine of Mineralogical and Petrological Sciences 38 ( 2 ) 33 - 38 2009年

記述言語：日本語

The electrical conductivity of the major upper mantle minerals, namely, olivine, wadsleyite and ringwoodite is reviewed in this paper. There are mainly three electrical conduction mechanisms for the major upper mantle minerals, namely, ionic, hopping and proton conductions. The charge carriers for these mechanisms are electron hole in Fe ion, vacancy in the Mg site and proton, respectively. An electron hole in an Fe ion forms a small polaron, which causes a higher activation energy (1.4-1.6 eV) than mere transfer of electron holes (0.1 eV). Hopping conduction is the most essential conduction mechanisms for the major upper mantle minerals. Ionic conduction is a dominant conduction mechanism only at high temperatures, because ionic conduction has high activation energy (4.3 eV for olivine). Proton conduction could play an important role because the major upper mantle minerals can contain certain amount of water. Proton conduction contributes more at lower temperatures because of its low activation energies (0.5-1.0 eV). If the mantle minerals contain large amount of water (&gt
0.1 wt%), proton conduction can be a dominant conduction mechanism of the mantle minerals even at high temperatures.

DOI： 10.2465/gkk.38.33

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

Electrical conductivity of majorite garnet and its implications for electrical structure in the mantle transition zone 査読

Takashi Yoshino, Masayuki Nishi, Takuya Matsuzaki, Daisuke Yamazaki, Tomoo Katsura

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 170 ( 3-4 ) 193 - 200 2008年11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 majorite garnet with compositions of pyrolite minus olivine (pyrolite majorite) and mid-ocean ridge basalt (MORB majorite) were measured under physical conditions of the mantle transition zone (18 and 23 GPa and temperatures up to 2000 K) in a Kawai-type multi-anvil apparatus. The samples with MORB composition are mainly composed of majorite, which has higher Fe and Al contents, and contain a small amount of stishovite. The conductivity of the MORB majorite is more than twice higher than those of the pyrolite majorite at the same temperature. The activation energies of these majorites are both 1.4 eV at temperature of 1000-1600 K suggesting that the dominant mechanism of charge transportation is Fe2(+)-Fe3(+) hopping (small polaron) conduction. At higher temperatures (>1600 K), corresponding to temperature conditions of the transition zone. conduction mechanism of the pyrolite majorite would change from small polaron to ionic conduction. The pyrolite majorite has only slightly higher and lower conductivity than dry wadsleyite and ringwoodite, respectively, and will not largely change the conductivity-depth profile predicted for the dry mantle transition zone. The laboratory-based conductivity profile of the mantle transition zone with pyrolitic composition can explain well the current semi-global conductivity-depth profile obtained from electromagnetic study beneath Pacific. On the other hand, the garnetite originating from the oceanic crust has remarkably higher conductivity than the surrounding mantle because the conductivity of MORB majorite is significantly higher than those of wadsleyite and ringwoodite. Conductivity values of MORB majorite agree with those of the stagnant slab beneath the northeastern China. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2008.04.009

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

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