Eiji Ito

Okayama University, Okayama, Okayama, Japan

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Publications (119)270.74 Total impact

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    ABSTRACT: 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 by the Kawai-type apparatus equipped with sintered diamond anvils. In both MnO and CoO, the cubic B1 lattice commences 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., contraction along the diagonal [111] direction of the B1 lattice in MnO and 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.
    Physics of The Earth and Planetary Interiors 01/2014; · 2.38 Impact Factor
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    ABSTRACT: 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, KT0, 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 KT0=299 (4) GPa and K’0=4.6 (0.2).
    Physics of The Earth and Planetary Interiors 01/2014; · 2.38 Impact Factor
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    ABSTRACT: γ-Ca3(PO4)2, naturally known as tuite, is regarded as an important potential reservoir for rare earth elements and large ion lithophile elements. It is a high-pressure polymorph of β-Ca3(PO4)2 whitlockite and a decomposed product of apatite under high-pressure and temperature. Drop-solution enthalpies of β- and γ-Ca3(PO4)2 were obtained as 298.59 ± 3.02 and 278.74 ± 2.98 kJ/mol, respectively, by the drop-solution calorimetry with 2PbO·B2O3 solvent at 978 K. Thus the enthalpy of transition from β- to γ-Ca3(PO4)2 at 298 K (ΔHtr,298o) was 19.85 ± 4.24 kJ/mol. The isobaric heat capacities of β- and γ-Ca3(PO4)2 were measured at temperature range of 300–770 K by differential scanning calorimetry, and compared with the results calculated from the Kieffer model. The equilibrium phase boundary between β- and γ-Ca3(PO4)2 was calculated using present measured data combined with other available thermochemical and thermoelastic data. The calculated boundary gave a phase transition boundary with a dP/dT slope of 4.7 ± 0.2 MPa/K in the temperature range of 900–2000 K. Based on the phase relationship, the occurrences of tuite and whitlockite in meteorites are discussed.
    Physics of The Earth and Planetary Interiors 01/2014; 228:144–149. · 2.38 Impact Factor
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    ABSTRACT: In our previous studies on the tolerance of living organisms such as planktons and spores of mosses to the high hydrostatic pressure of 7.5 GPa, we showed that all the samples could be borne at this high pressure. These studies have been extended to the extreme high pressure of 20 GPa by using a Kawai-type octahedral anvil press. It was found that the average diameter of the spores of Venturiella exposed to 20 GPa for 30 min was 25.5 μm, which is 16.5% smaller (40.0% smaller in volume) than that of the control group which was not exposed to high pressure. The inner organisms showed a further extent of plastic deformation. As a result, a gap appeared between the outer cover and the cytoplasm. A relationship has been obtained between the survival ratio and plastic deformation of spores of moss Venturiella caused by the application of ultra high pressure.
    High Pressure Research 06/2013; 33(2):362-368. · 0.90 Impact Factor
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    ABSTRACT: In order to determine the P-V-T equation of state of ɛ-iron, in situ X-ray observations were carried out at pressures up to 80 GPa and temperatures up to 1900 K using the Kawai-type high pressure apparatus equipped with sintered diamond anvils which was interfaced with synchrotron radiation. The present results indicate the unit cell volume at ambient conditions V0 = 22.15(5) Å3, the isothermal bulk modulus KT0 = 202(7) GPa and its pressure derivative K‧T0 = 4.5(2), the Debye temperature θ0 = 1173(62) K, Grüneisen parameter at ambient pressure γ0 = 3.2(2), and its logarithmic volume dependence q = 0.8(3). Furthermore, thermal expansion coefficient at ambient pressure was determined to be α0(K-1) = 3.7(2) × 10-5 + 7.2(6) × 10-8(T-300) and Anderson-Grüneisen parameter δT = 6.2(3). Using these parameters, we have estimated the density of ɛ-iron at the inner core conditions to be ˜3% denser than the value inferred from seismological observation. This result indicates that certain amount of light elements should be contained in the inner core as well as in the outer core but in definitely smaller amount.
    Geophysical Research Letters 10/2012; 39(20):20308-. · 3.98 Impact Factor
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    ABSTRACT: The electrical conductivity of olivine and its high-pressure polymorphs with various iron contents [XFe = Fe/(Fe + Mg) = 0.1, 0.2, 0.3, 0.5, 0.7 and 1.0] was measured over a wide range of pressure (P) and temperature (T) conditions covering the stability field of olivine, wadsleyite and ringwoodite in a Kawai-type multianvil apparatus. The pressure was determined using in situ X-ray diffraction of MgO as a pressure marker in SPring 8. Molybdenum electrodes were used so that oxygen fugacity is similar to that for the iron-wüstite buffer. The transition from low-pressure phase to high-pressure phase led to an increase of conductivity. In the stability field of each phase, the electrical conductivity slightly increased with increasing pressure at a constant temperature, suggesting a negative activation volume. The conductivity increased with increasing total iron content for each phase. All electrical conductivity data fit the formula for electrical conductivity σ = σ0 XFeexp{-[ΔE0 - αXFe1/3 + P(ΔV0 - βXFe)]/kT}, where σ0 is the pre-exponential term, ΔE0 and ΔV0 are the activation energy and the activation volume at very low total iron concentration, respectively, and k is the Boltzmann constant. The activation energy decreased with increasing total Fe content in olivine and ringwoodite. Dependence of the activation energy on the total Fe content suggests that the dominant mechanism of charge transport is Fe2+-Fe3+ hopping (small polaron). The activation volume for small polaron conduction in olivine and its high-pressure polymorphs tends to decrease with total Fe content. For olivine with low Fe content, the activation volume for small polaron conduction still is negative and very small. Assuming constant Fe content (XFe = 0.1) and oxygen buffer condition, the conductivity will increase with depth mainly due to the increase of the temperature along the mantle adiabat.
    Journal of Geophysical Research 08/2012; 117(B8):8205-. · 3.17 Impact Factor
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    ABSTRACT: We studied the tolerance of living organisms, such as a small animal (Milnesium tardigradum), a small crustacean (Artemia), non-vascular plants or moss (Ptichomitrium and Venturiella), and a vascular plant (Trifolium) to the extremely high hydrostatic pressure of 7.5 GPa. It turned out that most of the high pressure exposed seeds of white clover were alive. Those exposed to 7.5 GPa for up to 1 day and seeded on agar germinated roots. Those exposed for up to 1 hour and seeded on soil germinated stems and leaves. Considering the fact that proteins begins to unfold around 0.3 GPa, it seems difficult to understand that all the living samples which have been investigated can survive after exposure to 7.5 GPa.
    Journal of Physics Conference Series 01/2012; 377(1).
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    ABSTRACT: The pressure-induced electronic spin transition of iron in ferropericlase was investigated as a function of iron content in ferropericlase by in situ electrical conductivity measurement. The electrical conductivity of ferropericlase, (Mg1-x,Fex)O (x = 0.07, 0.10, 0.13, 0.17, 0.24) was measured up to 53 GPa and 600 K using the Kawai-type multi anvil apparatus equipped with sintered diamond anvils. At pressures up to 25 GPa, the electrical conductivity of ferropericlase generally increases with increasing pressure and both the activation energy and activation volume of ferropericlase decrease with increasing iron content. For the samples with x = 0.07 and 0.10, the electrical conductivity shows a slight initial decrease and becomes constant between 25 and 40 GPa upon which it increases slightly as the pressure increases. For the samples with higher iron content, the electrical conductivity constantly increases with pressure over the investigated pressure range. If these changes in the electrical conductivity are due to the isosymmetric high to low spin transition of iron in ferropericlase, this conductivity change suggests that the spin transition pressure significantly decreases with decreasing iron content in ferropericlase. Because the amount of iron in ferropericlase that coexists with the Al-bearing perovskite seems to be less than that in the Al-free perovskite, the influence of the iron partitioning between perovskite and ferropericlase by the spin transition appears in a pressure range of about 30-40 GPa in the lower mantle of the Earth.
    AGU Fall Meeting Abstracts. 12/2011;
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    American Mineralogist. 01/2011; 96:89-92.
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    ABSTRACT: A scaled-up version of a 6-8 Kawai-type multianvil apparatus equipped with 47-mm WC anvils has been developed at the Institute for the Study of the Earth's Interior for operation over pressure ranging up to 19 and 24 GPa using the conventional system with larger compressional volumes between 1.2 and 0.4 cm(3), respectively. This system is used under uniaxial compression along cube diagonal of the Kawai-cell up to the press load of 19 MN. Experiments are performed using octahedral pressure media (PM) made of MgO- and ZrO(2)-based semi-sintered ceramics and unfired pyrophyllite gaskets. In this study we used "Toshiba-F" grade WC anvils allowing pressure generation up to 24 GPa. We perform pressure calibrations at room and high temperatures, with octahedron/anvil truncation edge-length ratios (a(0)/b, mm) of 12.2/6, 14/6, 14/7, 16/7, 18/7, 18/9, and 18/10. Different configurations show that an increase in edge-length ratio of a(0)/b permits the achievement of higher pressure, which agrees with the results of Frost at al. (Frost, D.J., Poe, B.T., Tronnes, R.G., Liebske, C., Duba, A., Rubie, D.C., 2004. A new large-volume multianvil system. Phys. Earth Planet. Inter. 143, 507). However, it also shifts the pressure maximum to higher press loads, in some cases exceeding the capacity of a press. Our and Frost et al. (2004) data reveal that the 14/6, 18/8, and 18/10 assemblies are the most suitable in generating pressures of up to 19-24 GPa at 19 MN press load limits. The assemblies with a low a(0)/b ratio have a lower upper pressure limit; however, they exhibit a systematically higher efficiency in pressure generation at low press loads. Consequently, assemblages with high and low nab ratios should be used in high and low pressure experiments, respectively. For example, the 18/12 assembly is suitable for 5-11 GPa pressure range (Stoyanov, E., Haussermann, U., Leinenweber, K., 2010. Large-volume multianvil cells designed for chemical synthesis at high pressures. High Pressure Res., 30, 175), whereas the 14/6, 18/8 (Frost et al., 2004), and 18/10 assemblies are suitable for 22-24, 19-23, and 11-19 GPa pressure ranges, respectively. The maximum pressure generation achieved in the present study is 24 GPa, using the 14/6 assembly. This appears to be the maximum pressure level attainable by using WC anvils. (C) 2011 Elsevier B.V. All rights reserved.
    Physics of The Earth and Planetary Interiors 01/2011; 189(1-2):92-108. · 2.38 Impact Factor
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    ABSTRACT: Electrical conductivity of ferropericlaseDetermination of spin transition pressure of ferropericlaseEffect of iron content on spin transition pressure
    Journal of Geophysical Research 01/2011; 116. · 3.17 Impact Factor
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    ABSTRACT: The pyrochlore type of MgZrSi2O7 was synthesized at 25GPa and 1500°C using a Kawai-type, multi-anvil apparatus. Powder X-ray diffraction and Rietveld analysis revealed that the phase assumed the pyrochlore structure (space group Fd3¯m, cubic) with the lattice parameter a=9.2883(1)Å and the structural parameter x=0.4295(4). Chemical analysis by the electron probe microanalysis (EPMA) confirmed the stoichiometry of MgZrSi2O7. It was demonstrated that the eight-fold coordinated 16c site is randomly occupied by both Mg2+ and Zr4+ ions in a 1:1 ratio. The high ionic radius ratio RA/RB (where A and B denote Mg+Zr and Si, respectively) of 2.22 necessitates a relatively high pressure to stabilize the pyrochlore structure.
    Materials Chemistry and Physics - MATER CHEM PHYS. 01/2011; 128(3):410-412.
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    ABSTRACT: High-temperature Raman spectra and thermal expansion of tuite, γ-Ca3(PO4)2, have been investigated. The effect of temperature on the Raman spectra of synthetic tuite was studied in the range from 80 to 973K at atmospheric pressure. The Raman frequencies of all observed bands for tuite continuously decrease with increasing temperature. The quantitative analysis of temperature dependence of Raman bands indicates that the changes in Raman frequencies for stretching modes (ν3 and ν1) are faster than those for bending modes (ν4 and ν2) of PO4 in the present temperature range, which may be attributed to the structural evolution of PO4 tetrahedron in tuite at high temperature. The thermal expansion of tuite was examined by means of in situ X-ray diffraction measurements in the temperature range from 298 to 923K. Unit cell parameters and volume were analyzed, and the thermal expansion coefficients were obtained as 3.67 (3), 1.18 (1), and 1.32 (3)×10−5K−1 for V, a, and c, respectively. Thermal expansion of tuite shows an axial anisotropy with a larger expansion coefficient along the c-axis. The isothermal and isobaric mode Grüneisen parameters and intrinsic anharmonicity of tuite have been calculated by using present high-temperature Raman spectra and thermal expansion coefficient combined with previous results of the isothermal bulk modulus and high-pressure Raman spectra. KeywordsTuite–High-temperature–Raman spectra–Thermal expansion–X-ray diffraction–Grüneisen parameter–Intrinsic anharmonicity
    Physics and Chemistry of Minerals 01/2011; 38(8):639-646. · 1.30 Impact Factor
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    Shuangmeng Zhai, Eiji Ito
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    ABSTRACT: The tried and tested multianvil apparatus has been widely used for high-pressure and high-temperature experimental studies in Earth science. As a result, many important results have been obtained for a better understanding of the components, structure and evolution of the Earth. Due to the strength limitation of materials, the attainable multianvil pressure is generally limited to about 30 GPa (corresponding to about 900 km of the depth in the Earth) when tungsten carbide cubes are adopted as second-stage anvils. Compared with tungsten carbide, the sintered diamond is a much harder material. The sintered diamond cubes were introduced as second-stage anvils in a 6–8 type multianvil apparatus in the 1980s, which largely enhanced the capacity of pressure generation in a large volume press. With the development of material synthesis and processing techniques, a large sintered diamond cube (14 mm) is now available. Recently, maximum attainable pressures reaching higher than 90 GPa (corresponding to about 2700 km of the depth in the Earth) have been generated at room temperature by adopting 14-mm sintered diamond anvils. Using this technique, a few researches have been carried out by the quenched method or combined with synchrotron radiation in situ observation. In this paper we review the properties of sintered diamond and the evolution of pressure generation using sintered diamond anvils. As-yet unsolved problems and perspectives for uses in Earth Science are also discussed.
    Geoscience Frontiers. 01/2011; 2(1):101-106.
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    ABSTRACT: High pressure in situ synchrotron X-ray diffraction experiment of strontium orthophosphate Sr3(PO4)2 has been carried out to 20.0 GPa at room temperature using multianvil apparatus. Fitting a third-order Birch–Murnaghan equation of state to the P–V data yields a volume of V 0 = 498.0 ± 0.1 Å3, an isothermal bulk modulus of K T = 89.5 ± 1.7 GPa, and first pressure derivative of K T ′ = 6.57 ± 0.34. If K T ′ is fixed at 4, K T is obtained as 104.4 ± 1.2 GPa. Analysis of axial compressible modulus shows that the a-axis (K a = 79.6 ± 3.2 GPa) is more compressible than the c-axis (K c = 116.4 ± 4.3 GPa). Based on the high pressure Raman spectroscopic results, the mode Grüneisen parameters are determined and the average mode Grüneisen parameter of PO4 vibrations of Sr3(PO4)2 is calculated to be 0.30(2).
    Physics and Chemistry of Minerals 01/2011; 38(5):357-361. · 1.30 Impact Factor
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    ABSTRACT: (Mg,Fe)SiO3 perovskite and ferro-periclase are abundant minerals in the Earth's lower mantle and hence their pressure-volume-temperature (P-V-T) relations are very useful in interpreting the seismological observations. Previous researches suggested the significant change of compressibility (P-V relation) of ferro-periclase due to the spin transition in iron at pressure of 30-70 GPa (Fei et al., 2008; Ito et al, 2010), whereas compressibility change caused by spin transition in (Mg,Fe)SiO3 perovskite is not reported yet. Iron content in silicate perovskite is much lower than that in ferro-periclase and pressures for spin transition in perovskite is expected to be higher than 70 GPa. Therefore, precise determination of volume at wide pressure range is required to access the change of P-V relation associated with spin transition in perovskite. Although pressure range in Kawai-type multianvil high pressure apparatus (KMA) is insufficient to cover whole mantle conditions, KMA enables us to have a large sample and uniform heating for high temperature experiment. In this study, we developed the experimental technique to expand the pressure range in KMA and applied this technique to measure the volumes of MgSiO3 and (Mg,Fe)SiO3 perovskites to observe the change in P-V curve related to spin transition. We conducted high pressure experiments at synchrotron facility, SPring-8, Japan, using a KMA equipped with sintered diamond anvils with 1.0 mm truncated edge length, and we succeeded to expand the pressure limit to ~ 95 GPa (at press of 6.5 MN) at 700 K based on Au pressure standard (Tsuchiya, 2003). In the experiment, we measured the volumes of MgSiO3 and (Mg,Fe)SiO3 perovskites simultaneously as a function of temperature and pressure. In this pressure range, little change in the volume ratio between MgSiO and (Mg,Fe)SiO3 perovskites is expected by preliminary volume analyses. We re-calculate the volumes and expand pressure range more and more in future.
    AGU Fall Meeting Abstracts. 12/2010;
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    ABSTRACT: We have improved performance of the Kawai-type multi anvil apparatus by adopting sintered diamond anvils with an edge length of 14 mm and a truncated corner of 1.0 mm. Most experiments have been carried out at synchrotron facility SPring-8 in Japan. The Kawai-cell (an assemblage of eight cubic anvils and an octahedral specimen) has been squeezed in the DIA-type apparatus installed on the beam line BL04B1. Sample mixed with pressure standard such as Au has been examined by in situ X-ray diffraction method, and the experimental pressure is simultaneously determined from measured volume of the standard material via its EoS. Recently maximum attainable pressure exceeded 95 GPa [Ito et al., 2010]. Based on the experimental innovation, we have investigated the high spin (HS) to low spin (LS) transition of Fe2+ in (Mg1-xFex) ferropericlase (Fp) under lower mantle conditions. Since the effective ionic radius of Fe2+ in LS state is substantially smaller than that in HS state, the spin transition brings about a definite volume contraction together with an increase in bulk modulus. The progressive transition in Fp solid solution with pressure causes a regime of mixed spin state at pressures between those of HS and LS states. The feature should be realized along a P-V compression curve [e.g., Lin and Tsuchiya, 2008]. We have acquired the P-V data of (Mg0.83Fe0.17)O Fp up to 90 GPa and at 300 and 700 K with errors less than ±0.006 Å3 in volume and ±0.4 GPa in pressure. Pressure determination is based on the Anderson et al's [1989] Au scale. From detailed analysis of the data by fitting the 3rd order Birch-Murnaghan EoS, it has been concluded that the spin transition proceeds over pressure ranges from 50 to 70 GPa at 300 K and from 60 to 85 GPa.
    AGU Fall Meeting Abstracts. 12/2010;
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    ABSTRACT: Thermal diffusivity and thermal conductivity of serpentine (antigorite) were measured up to 8.5 GPa and 800 K in the Kawai-type high-pressure apparatus. Antigorite has thermal diffusivity of 0.90 × 10 -6 m 2 s -1 and thermal conductivity of 2.7 W m -1 K -1 at 5 GPa and 300 K, which are much lower than those of olivine. Furthermore, the pressure derivatives of thermal diffusivity and thermal conductivity are significantly smaller than those of olivine. The thermal properties of antigorite obtained in the present study imply existence of a thermal insulating layer in subduction zones. From the simultaneous measurement of both thermal diffusivity and thermal conductivity the heat capacity of antigorite was determined to be ≈1 × 10 3 J kg -1 K -1, and increased to ≈1.5 × 10 3 J kg -1 K -1 at ≈800 K under high pressure. The heat capacity was nearly independent of pressure, which indicates nearly temperature-independent thermal expansivity of antigorite. Its characteristics also were hypothesized in terms of lattice dynamics of hydrous minerals involving hydrogen atoms and hydroxyl groups.
    Physics of The Earth and Planetary Interiors 11/2010; 183(1-2):229-233. · 2.38 Impact Factor
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    ABSTRACT: 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.
    Journal of Physics Conference Series 04/2010; 215(1):012099.
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    ABSTRACT: 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 (Mg0.9,Fe0.1)SiO3, 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.
    Journal of Physics Conference Series 04/2010; 215(1):012102.

Publication Stats

2k Citations
270.74 Total Impact Points

Institutions

  • 1989–2014
    • Okayama University
      • Institute for Study of the Earth's Interior
      Okayama, Okayama, Japan
  • 2009
    • University of Hyogo
      • School of Science
      Kōbe-shi, Hyogo-ken, Japan
    • Peking University
      • School of Earth and Space Sciences
      Beijing, Beijing Shi, China
  • 2008
    • Northeast Institute of Geography and Agroecology
      • Institute of Physics
      Beijing, Beijing Shi, China
    • The University of Tokyo
      • Institute for Solid State Physics
      Tokyo, Tokyo-to, Japan
  • 2007
    • University of Illinois, Urbana-Champaign
      • Department of Geology
      Urbana, IL, United States