Faculty Profiles - Ishii Takayuki

Papers - Ishii Takayuki

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Synthesis, Stability, and Crystal Structure of CaTi₂O₄-Type ZnCr₂O₄: High-Pressure Crystal Chemistry of Postspinel Phases Reviewed

Takayuki Ishii, Yudai Masaki, Alan B. Woodland, Yoshiyuki Inaguma, Hiroshi Kojitani, Masaki Akaogi

Inorganic Chemistry 2025.6

Stability and water solubility of calcium ferrite-type aluminum-rich phase: implications for deep water cycle caused by subducting basaltic crusts

Xinyue Zhang, Izumi Mashino, Takayuki Ishii

Progress in Earth and Planetary Science 2025.5

Limited water contents of wadsleyite and ringwoodite coexisting with hydrous minerals in cold subducting slabs

Takayuki Ishii, Jintao Zhu, Eiji Ohtani

Earth and Planetary Science Letters 2025.5

Iron hydride (FeHx) as a crucial intermediate in transformation of subducted H2O to abiotic H2 in Earth’s deep mantle Reviewed

Jintao Zhu, Renbiao Tao, Takayuki Ishii, Daijo Ikuta, Wenbo Xu, Lifei Zhang, Yutong Su, Runchao Liu, Zhijun Jin

Science China Earth Sciences 68 ( 5 ) 1485 - 1496 2025.4

The effect of Fe incorporation on the single-crystal elasticity of δ-AlOOH Reviewed

Niccolò Satta, Giacomo Criniti, Tiziana Boffa Ballaran, Alexander Kurnosov, Takayuki Ishii, Johannes Buchen, Hauke Marquardt

Physics and Chemistry of Minerals 52 ( 2 ) 2025.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

The seismic mapping of hydrous materials in the Earth’s deep interior requires experimental constraints on the elastic anisotropy of hydrous minerals and phases. Oxyhydroxides like δ-(Al,Fe)OOH are arguably the main hosts of water in the lower mantle. Therefore, constraints on the single-crystal elastic tensor of δ-(Al,Fe)OOH solid solutions are crucial to quantify the elastic anisotropy of this material, and advance the current understanding of the recycling of water into the lower mantle. Yet, experimental data for intermediate compositions are scarce, limiting the understanding of how Fe incorporation affects the single-crystal elastic properties of δ-AlOOH. In this study, we provide experimental constraints on the single-crystal elasticity of two δ-(Al,Fe)OOH solid solutions, with Fe/(Al + Fe) of 0.06(1) and 0.133(3). Large single-crystal samples of δ-(Al,Fe)OOH were synthetized at high pressures and temperatures using a multi-anvil press, and the full elastic stiffness tensors were determined at ambient conditions by combining X-ray diffraction and Brillouin scattering measurements. We show that replacing Al³⁺ with Fe³⁺ in δ-(Al,Fe)OOH lowers the magnitude of most coefficients of the elastic stiffness tensor (c _ij), which translates into a substantial reduction of aggregate moduli and acoustic wave velocities. We further show that, at ambient conditions, the acoustic anisotropy of δ-(Al,Fe)OOH displays no sensitivity to Fe–Al substitution.

DOI： 10.1007/s00269-025-01319-7

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Other Link： https://link.springer.com/article/10.1007/s00269-025-01319-7/fulltext.html

Effect of chemistry on the compressibility and high-pressure structural evolution of the CaFe2O4-type aluminous silicate phase Reviewed

Giacomo Criniti, Tiziana Boffa Ballaran, Alexander Kurnosov, Takayuki Ishii, Elena-Marie Rogmann, Konstantin Glazyrin, Timofey Fedotenko, Daniel J. Frost

Physics of the Earth and Planetary Interiors 361 107331 - 107331 2025.4

Development of high pressure-temperature experimental techniques and studies of phase relations and crystal chemistry of mantle minerals Reviewed

Takayuki ISHII

Japanese Magazine of Mineralogical and Petrological Sciences 54 ( 1 ) n/a - n/a 2025.2

Reduced Thermal Conductivity of Hydrous Aluminous Silica and Calcium Ferrite‐Type Phase Promote Water Transportation to Earth's Deep Mantle

Wen‐Pin Hsieh, Takayuki Ishii, Frédéric Deschamps, Yi‐Chi Tsao, Jen‐Wei Chang, Giacomo Criniti

Journal of Geophysical Research: Solid Earth 2025.1

Enhanced optical anisotropy of six-coordinated silica polymorphs via high-pressure hydrothermal treatment Reviewed

Junwei Li, Yanqiang Li, Weiqi Huang, Takayuki Ishii, Yanhao Lin, Binbin Yue, Sangen Zhao, Qingyang Hu

Journal of Materials Chemistry C 13 ( 3 ) 1499 - 1506 2025

Role of water in dynamics of slabs and surrounding mantle Reviewed

Eiji Ohtani, Takayuki Ishii

Progress in Earth and Planetary Science 11 ( 1 ) 2024.12

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

Water bound to various hydrous minerals can be transported deep into the mantle by slab subduction. Serpentine is one of most important hydrous minerals in the crust and shallow upper mantle. A partially serpentinized slab mantle limits the amount of water that can enter deep into the mantle. The partitioning of water between hydrous minerals and nominally anhydrous minerals (NAMs) is a crucial factor in controlling the physical properties and dynamics of slabs. Recent experiments on water partitioning have revealed that water strongly partitions to coexisting hydrous minerals. NAMs, such as olivine and its high-pressure polymorphs, have limited water content in water-undersaturated wet slabs. Metastable olivine wedges are not a feature of dry slabs, but can be of wet slabs that are not saturated with water. The transformation kinetics of the dry state, which generates deep-focus earthquakes and produces significant deformation in the slab, can work under wet slabs. Water bound to hydrous minerals is transported by the slab to the mantle transition zone and lower mantle. Hydrous minerals in stagnant slabs over 660 km depth release water as the slab warms, producing locally hydrated mantle transition zones and dense water-bearing magmas at the base of the upper mantle, and generating intraplate volcanism, which are referred to as the big mantle wedge model. Seismic scatterers are observed in the lower mantle at depths from 700 to 1900 km. These scatterers may be caused by water release at the top of the lower mantle by dehydration of hydrous minerals such as dense hydrous magnesium silicates. The shear instability due to the second order phase transformation from stishovite to CaCl₂-type phase in hydrous aluminous SiO₂ also causes the depth variation of seismic scatterers in the lower mantle. The high-pressure polymorphs of aluminous SiO₂ contain a large amount of water more than 1 wt%, which can be important water carriers under lower mantle conditions.

DOI： 10.1186/s40645-024-00670-7

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Other Link： https://link.springer.com/article/10.1186/s40645-024-00670-7/fulltext.html

Elastic anomalies across the P21nm→Pnnm structural phase transition in δ-(Al,Fe)OOH Reviewed

Niccolò Satta, Giacomo Criniti, Alexander Kurnosov, Tiziana Boffa Ballaran, Takayuki Ishii, Hauke Marquardt

American Mineralogist 109 ( 11 ) 1934 - 1944 2024.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Mineralogical Society of America

Abstract

Hydrogen may be recycled into the Earth’s lower mantle by subduction and stabilized in solid solutions between phase H (MgSiO4H2), δ-AlOOH, ε-FeOOH, and SiO2 post-stishovite. In high-pressure oxyhydroxide phases, hydrogen is incorporated following the typical (OHO) sequence, adopting the asymmetric configuration O-H···O that evolves into a symmetric disordered state upon compression. Moreover, these iron-bearing aluminum oxyhydroxides [δ-(Al,Fe)OOH] present a structural phase transition from P21nm to Pnnm as pressure increases. Here, the single-crystal elasticity of the P21nm phase of δ-(Al0.97Fe0.03)OOH has been experimentally determined across the P21nm→Pnnm transition up to 7.94(2) GPa by simultaneous single-crystal X-ray diffraction (XRD) and Brillouin scattering at high pressures. The transition appears to be continuous, and it can be described with a second-, fourth-, and sixth-order terms Landau potential. Our results reveal an enhanced unit-cell volume compressibility, which is linked to an increase of the b- and a-axes linear compressibility in the P21nm phase of δ-(Al0.97Fe0.03)OOH prior to the transition. In addition, we observed the presence of elastic softening in the P21nm phase that mostly impacts the elastic stiffness coefficients c12, c22, and c23. The observed elastic anomalies cause a significant change in the pressure dependence of the adiabatic bulk modulus (KS). These results provide a better understanding of the relation between elasticity, P21nm→Pnnm structural phase transition, and hydrogen dynamics in δ-(Al0.97Fe0.03)OOH, which may be applied to other O-H···O-bearing phases.

DOI： 10.2138/am-2023-9129

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Post-spinel-type AB2O4 high-pressure phases in geochemistry and materials science

Masaki Akaogi, Takayuki Ishii, Kazunari Yamaura

Communications Chemistry 7 ( 1 ) 2024.8

Synthesis and Crystal Structure of Ilmenite-Type Silicate with Pyrope Composition

Takayuki Ishii, Ryosuke Sinmyo, Tomoo Katsura

Solids 2024.8

Melting at the base of a terrestrial magma ocean controlled by oxygen fugacity Reviewed

Yanhao Lin, Takayuki Ishii, Wim van Westrenen, Tomoo Katsura, Ho-Kwang Mao

Nature Geoscience 17 ( 8 ) 803 - 808 2024.7

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

Heat delivered from accretionary impacts is thought to have led to extensive melting of early Earth’s silicate mantle, resulting in a deep magma ocean covering the surface. The mantle’s oxygen fugacity is thought to have increased over accretion and core formation due to increasingly oxidated impactors and lower mantle self-oxidation, but the influence of this on the solidus of deep primitive mantle materials has not been well constrained. Here we assess the effect of oxygen fugacity on conditions at the bottom of a magma ocean by experimentally determining the solidus of mantle pyrolite at pressures of 16–26 GPa at high oxygen fugacities. We find that over this pressure range, the solidus in experiments conducted under oxidizing conditions is at least 230–450 °C lower than in experiments conducted under more reducing conditions. Assuming constant magma ocean temperature, this would imply a magma ocean floor that deepens by about 60 km for each log unit increase in mantle oxygen fugacity. The strong influence of oxygen fugacity on mantle melting suggests that models of early Earth thermal evolution and geochemical models of core formation should be reassessed.

DOI： 10.1038/s41561-024-01495-1

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Other Link： https://www.nature.com/articles/s41561-024-01495-1

K- and Na-rich davemaoite inclusion in diamond is not inherited from deeply subducted oceanic crusts Reviewed

Wenqing Sun, Renbiao Tao, Jintao Zhu, Chao Wang, Takayuki Ishii, Yunxiu Li

Earth and Planetary Science Letters 637 118741 - 118741 2024.7

Inert structural transition in 4H and 6H SiC at high pressure and temperature: a Raman spectroscopy study

Shuhou Maitani, Ryosuke Sinmyo, Takayuki Ishii, Kenji Yoza

Journal of Physics Communications 8 ( 6 ) 2024.6

Hydrogen partitioning between stishovite and hydrous phase δ: implications for water cycle and distribution in the lower mantle Reviewed

Takayuki Ishii, Giacomo Criniti, Narangoo Purevjav, Tomoo Katsura, Eiji Ohtani

Progress in Earth and Planetary Science 2024.2

Temperature Dependence of H₂O Solubility in Al‐Free Stishovite Reviewed

Narangoo Purevjav, Hongzhan Fei, Takayuki Ishii, Giacomo Criniti, Yanhao Lin, Ho‐Kwang Mao, Tomoo Katsura

Geophysical Research Letters 51 ( 3 ) 2024.2

Publishing type：Research paper (scientific journal) Publisher：American Geophysical Union (AGU)

Abstract

The role of stishovite in transporting water in subducting slabs has been a subject of debate for several decades. Here we investigated stishovite's water solubility and its potential role in water transportation as a function of temperature from 1300 to 2100°C at 22 GPa. Under water‐saturated conditions, high‐quality, Al‐free stishovite single crystals were synthesized with multi‐anvil press, and their water contents were measured using infrared spectroscopy. The H₂O solubility in stishovite increases from 128(20) to 521(47) wt. ppm with increasing temperature from 1300 to 1700°C and decreased to 145(26) wt. ppm at 2100°C. The maximum H₂O content was about seven times larger than earlier high‐temperature multi‐anvil studies but significantly lower than recent laser‐heated diamond anvil cell and low‐temperature multi‐anvil studies. We suggest that Al‐free stishovite may not be a significant H₂O carrier in subducting slabs, at least at the topmost lower mantle corresponding to our experimental conditions.

DOI： 10.1029/2023gl104029

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Crystal chemistry and compressibility of Fe0.5Mg0.5Al0.5Si0.5O3 and FeMg0.5Si0.5O3 silicate perovskites at pressures up to 95 GPa Reviewed

Iuliia Koemets, Biao Wang, Egor Koemets, Takayuki Ishii, Zhaodong Liu, Catherine McCammon, Artem Chanyshev, Tomo Katsura, Michael Hanfland, Alexander Chumakov, Leonid Dubrovinsky

Frontiers in Chemistry 11 2023.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Frontiers Media SA

Silicate perovskite, with the mineral name bridgmanite, is the most abundant mineral in the Earth’s lower mantle. We investigated crystal structures and equations of state of two perovskite-type Fe³⁺-rich phases, FeMg_0.5Si_0.5O₃ and Fe_0.5Mg_0.5Al_0.5Si_0.5O₃, at high pressures, employing single-crystal X-ray diffraction and synchrotron Mössbauer spectroscopy. We solved their crystal structures at high pressures and found that the FeMg_0.5Si_0.5O₃ phase adopts a novel monoclinic double-perovskite structure with the space group of P21/n at pressures above 12 GPa, whereas the Fe_0.5Mg_0.5Al_0.5Si_0.5O₃ phase adopts an orthorhombic perovskite structure with the space group of Pnma at pressures above 8 GPa. The pressure induces an iron spin transition for Fe³⁺ in a (Fe_0.7,Mg_0.3)O₆ octahedral site of the FeMg_0.5Si_0.5O₃ phase at pressures higher than 40 GPa. No iron spin transition was observed for the Fe_0.5Mg_0.5Al_0.5Si_0.5O₃ phase as all Fe³⁺ ions are located in bicapped prism sites, which have larger volumes than an octahedral site of (Al_0.5,Si_0.5)O₆.

DOI： 10.3389/fchem.2023.1258389

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Structure and compressibility of Fe-bearing Al-phase D Reviewed

Giacomo Criniti, Takayuki Ishii, Alexander Kurnosov, Konstantin Glazyrin, Rachel J. Husband, Tiziana Boffa Ballaran

American Mineralogist 108 ( 9 ) 1764 - 1772 2023.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Mineralogical Society of America

Abstract

Due to its large thermal stability, Al-phase D, the (Al,Fe3+)2SiO6H2 member of the dense hydrous magnesium silicate (DHMS) phase D, may survive along hot subduction geotherms or even at ambient mantle temperatures in the Earth’s transition zone and lower mantle, therefore potentially playing a major role as a water reservoir and carrier in the Earth’s interior. We have investigated the crystal structure and high-pressure behavior of Fe-bearing Al-phase D with a composition of Al1.53(2)Fe0.22(1) Si0.86(1)O6H3.33(9) by means of single-crystal X-ray diffraction. While the structure of pure Al-phase D (Al2SiO6H2) has space group P63/mcm and consists of equally populated and half-occupied (Al,Si)O6 octahedra, Fe-incorporation in Al-phase D seems to induce partial ordering of the cations over the octahedral sites, resulting in a change of the space group from P63/mcm to P6322 and in well-resolved diffuse scattering streaks observed in X-ray images. The evolution of the unit-cell volume of Fe-bearing Al-phase D between room pressure and 38 GPa, determined by means of synchrotron X-ray diffraction in a diamond anvil cell, is well described by a third-order Birch-Murnaghan equation of state having an isothermal bulk modulus KT0 = 166.3(15) GPa and first pressure derivative KT0′ = 4.46(12). Above 38 GPa, a change in the compression behavior is observed, likely related to the high-to-low spin crossover of octahedrally coordinated Fe3+. The evolution of the unit-cell volume across the spin crossover was modeled using a recently proposed formalism based on crystal-field theory, which shows that the spin crossover region extends from approximately 30 to 65 GPa. Given the absence of abrupt changes in the compression mechanism of Fe-bearing Al-phase D before the spin crossover, we show that the strength of H-bonds and likely their symmetrization do not greatly affect the elastic properties of phase D solid solutions, independently of their compositions.

DOI： 10.2138/am-2022-8559

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High-Pressure Phase Relations and Element Partitioning of Minerals in Hydrous Systems Invited Reviewed

Takayuki ISHII, Eiji OHTANI

The Review of High Pressure Science and Technology 33 ( 3 ) 179 - 186 2023.9

Buoyancy of slabs and plumes enhanced by curved post-garnet phase boundary Reviewed

Takayuki Ishii, Daniel J. Frost, Eun Jeong Kim, Artem Chanyshev, Keisuke Nishida, Biao Wang, Rintaro Ban, Jianing Xu, Jin Liu, Xiaowan Su, Yuji Higo, Yoshinori Tange, Ho-kwang Mao, Tomoo Katsura

Nature Geoscience 2023.9

High-pressure phase transition and equation of state of hydrous Al-bearing silica Reviewed

Giacomo Criniti, Takayuki Ishii, Alexander Kurnosov, Konstantin Glazyrin, Tiziana Boffa Ballaran

American Mineralogist 108 ( 8 ) 1558 - 1568 2023.8

Iron and aluminum substitution mechanism in the perovskite phase in the system MgSiO3-FeAlO3-MgO Reviewed

Takayuki Ishii, Catherine McCammon, Tomoo Katsura

American Mineralogist 108 ( 4 ) 738 - 743 2023.4

Authorship：Lead author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：Mineralogical Society of America

Abstract

Fe,Al-bearing MgSiO3 perovskite (bridgmanite) is considered to be the most abundant mineral in Earth’s lower mantle, hosting ferric iron in its structure as charge-coupled (Fe2O3 and FeAlO3) and vacancy components (MgFeO2.5 and Fe2/3SiO3). We examined concentrations of ferric iron and aluminum in the perovskite phase as a function of temperature (1700–2300 K) in the MgSiO3-FeAlO3-MgO system at 27 GPa using a multi-anvil high-pressure apparatus. We found a LiNbO3-structured phase in the quenched run product, which was the perovskite phase under high pressures and high temperatures. The perovskite phase coexists with corundum and a phase with (Mg,Fe3+,☐)(Al,Fe3+)2O4 composition (☐ = vacancy). The FeAlO3 component in the perovskite phase decreases from 69 to 65 mol% with increasing temperature. The Fe2O3 component in the perovskite phase remains unchanged at ~1 mol% with temperature. The A-site vacancy component of Fe2/3SiO3 in the perovskite phase exists as 1–2 mol% at 1700–2000 K, whereas 1 mol% of the oxygen vacancy component of MgFeO2.5 appears at higher temperatures, although the analytical errors prevent definite conclusions. The A-site vacancy component might be more important than the oxygen vacancy component for the defect chemistry of bridgmanite in slabs and for average mantle conditions when the FeAlO3 charge-coupled component is dominant.

DOI： 10.2138/am-2022-8457

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Equation of State and Spin Crossover of (Al, Fe)‐Phase H Reviewed

Benjamin Strozewski, Johannes Buchen, Wolfgang Sturhahn, Takayuki Ishii, Itaru Ohira, Stella Chariton, Barbara Lavina, Jiyong Zhao, Thomas S. Toellner, Jennifer M. Jackson

Journal of Geophysical Research: Solid Earth 128 ( 4 ) 2023.4

Ferric Iron Substitution Mechanism in Bridgmanite under SiO₂-Saturated Conditions at 27 GPa Reviewed

Artem Chanyshev, Hongzhan Fei, Dmitry Bondar, Biao Wang, Zhaodong Liu, Takayuki Ishii, Robert Farla, Catherine McCammon, Tomoo Katsura

ACS Earth and Space Chemistry 7 ( 2 ) 471 - 478 2023.2

Stability of Fe5O6 and its relation to other Fe-Mg-oxides at high pressures and temperatures Reviewed

Alan B. Woodland, Laura Uenver-Thiele, Tiziana Boffa Ballaran, Nobuyoshi Miyajima, Kevin Rosbach, Takayuki Ishii

American Mineralogist 108 ( 1 ) 140 - 149 2023.1

Authorship：Last author Publishing type：Research paper (scientific journal) Publisher：Mineralogical Society of America

Abstract

The stability of Fe5O6 has been experimentally determined under pressure-temperature conditions relevant for the Earth’s deeper upper mantle down to the upper portion of the lower mantle (to 28 GPa). In addition, we investigated the incorporation of Mg into Fe5O6 and its systematics, which allows us to discuss the relevance of this phase for the mantle. Experiments were performed from 8–28 GPa and 900–1600 °C. Additional oxide phases may appear if the bulk composition does not maintain the Fe32+Fe23+O6 stoichiometry during the experiment, including coexisting Fe4O5 or Fe9O11. Unfortunately, the similarities in Raman spectra between several high-pressure Fe-oxide phases make this method unsuitable for distinguishing which phase is present in a given sample. The stability field for Fe5O6 extends from ~9 to at least 28 GPa but is truncated at lower temperatures by the assemblage Fe4O5 + wüstite. Refined thermodynamic properties for Fe5O6 are presented. The range of redox stability of Fe5O6 appears to be more limited than that of Fe4O5.

Solid solution along the Fe5O6-Mg3Fe2O6 binary is quite limited, reaching a maximum Mg content of ~0.82 cations per formula unit (i.e., XMg3Fe2O6 ≈ 0.27) at 1400 °C and 10 GPa. The observed sharp decrease in molar volume of the O6-phase with Mg content could be a possible explanation for the limited range of solid solution. A phase diagram has been constructed for a composition of approximately Mg0.5Fe2.52+Fe23+O6 stoichiometry. This small amount of Mg causes a significant change in the relations between the O6-structured phase and the assemblage O5-structured phase + (Mg,Fe)O. Several experiments were performed to test whether the O6-phase can coexist with mantle silicates like wadsleyite and ringwoodite. In all cases, the run products contained (Mg,Fe)2Fe2O5 rather than the O6-phase, further underlining the limited ability of Fe5O6 to accommodate enough Mg to be stable in a mantle assemblage.

The large stability field of Fe5O6 implies that this phase could likely occur in locally Fe-rich environments, like those sampled by some “deep” diamonds. However, the limited solubility of Mg in the O6-phase leads us to conclude that the O5-phase should be of much more relevance as an accessory phase in a peridotitic mantle assemblage.

DOI： 10.2138/am-2022-8370

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Synthesis and structural analysis of CaFe2O4-type single crystals in the NaAlSiO4-MgAl2O4-Fe3O4 system Reviewed

Takayuki Ishii, Giacomo Criniti, Xiaoyu Wang, Konstantin Glazyrin, Tiziana Boffa Ballaran

American Mineralogist 108 ( 1 ) 217 - 221 2023.1

Authorship：Lead author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：Mineralogical Society of America

Abstract

Orthorhombic CaFe2O4-structured (Cf) Na-rich aluminous silicate (space group Pbnm) is a major mineral of metabasaltic rocks at lower mantle conditions and can, therefore, significantly affect the physical properties of subducted oceanic crusts. We attempted to synthesize single crystals of Cf-type phases in the systems NaAlSiO4, NaAlSiO4-MgAl2O4, NaAlSiO4-MgAl2O4-Fe3O4, and NaAlSiO4-MgAl2O4-Fe3O4-H2O at 23–26 GPa and 1100–2200 °C. Under dry conditions, single crystals of Cf-type phase up to 100–150 μm in size were recovered from 23 GPa and 2000–2200 °C. Single-crystal X-ray diffraction and composition analyses suggest that the synthesized Cf-type phases have a few percent of vacancies in the eightfold-coordinated site with Na, Mg, and Fe2+ and partially disordered Al and Si in the octahedral sites. Iron-bearing Cf-type phases have 32–34% Fe3+ that is hosted both in the octahedral sites and in the eightfold-coordinated site. In NaAlSiO4-MgAl2O4-Fe3O4-H2O system, no formation of Cf-type phase was observed at 24 GPa and 1100–2000 °C due to the formation of hydrous Na-rich melt and Al-rich oxides or hydroxides, suggesting the possible absence of Cf-type phase in the hydrous basaltic crust. The single-crystal syntheses of Cf-type phases will be useful for investigating their physical properties, potentially improving models of lower mantle structure and dynamics.

DOI： 10.2138/am-2022-8748

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The influence of Al2O3 on the structural properties of MgSiO3 akimotoite Reviewed

Nicki C. Siersch, Giacomo Criniti, Alexander Kurnosov, Tiziana Boffa Ballaran, Zhaodong Liu, Takayuki Ishii, Daniel J. Frost, Tony Yu, Yanbin Wang

American Mineralogist 108 ( 1 ) 100 - 109 2023.1

Publishing type：Research paper (scientific journal) Publisher：Mineralogical Society of America

Abstract

Akimotoite, a MgSiO3 polymorph present in the lower transition zone within ultramafic portions of subducting slabs and potentially also in the ambient mantle, will partition some amount of Al, raising the question of how this will affect its crystal structure and properties. In this study, a series of samples along the MgSiO3-Al2O3 (akimotoite-corundum) solid solution have been investigated by means of single-crystal X-ray diffraction to examine their crystal chemistry. Results show a strong nonlinear behavior of the a- and c-axes as a function of Al content, which arises from fundamentally different accommodation mechanisms in the akimotoite and corundum structures. Furthermore, two Al2O3-bearing akimotoite samples were investigated at high pressure to determine the different compression mechanisms associated with Al substitution. Al2O3-bearing akimotoite becomes more compressible at least up to 20 mol% Al2O3, due likely to an increase in compressibility as the Al cation is incorporated into the SiO6 octahedron. This observation is in strong contrast to the stiffer corundum end-member having a KT = 250 GPa, which is larger than that of the akimotoite end-member [KT = 205(1) GPa]. These findings have implications for mineral physics models of elastic properties, which have in the past assumed linear mixing behavior between the MgSiO3 akimotoite and Al2O3 corundum end-members to calculate sound wave velocities for Al-bearing akimotoite at high pressure and temperature.

DOI： 10.2138/am-2022-8257

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Superhydrous aluminous silica phases as major water hosts in high-temperature lower mantle Reviewed

Takayuki Ishii, Giacomo Criniti, Eiji Ohtani, Narangoo Purevjav, Hongzhan Fei, Tomoo Katsura, Ho-kwang Mao

Proceedings of the National Academy of Sciences 119 ( 44 ) 2022.10

Authorship：Lead author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：Proceedings of the National Academy of Sciences

Water transported by subducted oceanic plates changes mineral and rock properties at high pressures and temperatures, affecting the dynamics and evolution of the Earth’s interior. Although geochemical observations imply that water should be stored in the lower mantle, the limited amounts of water incorporation in pyrolitic lower-mantle minerals suggest that water in the lower mantle may be stored in the basaltic fragments of subducted slabs. Here, we performed multianvil experiments to investigate the stability and water solubility of aluminous stishovite and CaCl ₂ -structured silica, referred to as poststishovite, in the SiO ₂ -Al ₂ O ₃ -H ₂ O systems at 24 to 28 GPa and 1,000 to 2,000 °C, representing the pressure–temperature conditions of cold subducting slabs to hot upwelling plumes in the top lower mantle. The results indicate that both alumina and water contents in these silica minerals increase with increasing temperature under hydrous conditions due to the strong Al ³⁺ -H ⁺ charge coupling substitution, resulting in the storage of water up to 1.1 wt %. The increase of water solubility in these hydrous aluminous silica phases at high temperatures is opposite of that of other nominally anhydrous minerals and of the stability of the hydrous minerals. This feature prevents the releasing of water from the subducting slabs and enhances the transport water into the deep lower mantle, allowing significant amounts of water storage in the high-temperature lower mantle and circulating water between the upper mantle and the lower mantle through subduction and plume upwelling. The shallower depths of midmantle seismic scatterers than expected from the pure SiO ₂ stishovite–poststishovite transition pressure support this scenario.

DOI： 10.1073/pnas.2211243119

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Sound Velocity Measurements of B2‐Fe‐Ni‐Si Alloy Under High Pressure by Inelastic X‐Ray Scattering: Implications for the Composition of Earth's Core Reviewed

S. Dominijanni, C. A. McCammon, E. Ohtani, D. Ikuta, T. Sakamaki, T. Ishii, G. Criniti, L. S. Dubrovinsky, S. Khandarkhaeva, T. Fedotenko, K. Glazyrin, H. Uchiyama, H. Fukui, A. Q. R. Baron

Geophysical Research Letters 49 ( 15 ) 2022.8

Publishing type：Research paper (scientific journal) Publisher：American Geophysical Union (AGU)

Abstract

Elastic properties of B2‐Fe_0.67Ni_0.06Si_0.27 (15 wt.% Si) alloy have been investigated by combined high‐resolution inelastic X‐ray scattering and powder X‐ray diffraction in diamond anvil cells up to 100 GPa at room temperature. Densities (ρ), compressional (V_P) and shear (V_S) wave velocities were extrapolated to inner core conditions to enable comparison with the preliminary reference Earth model. The modeled aggregate compressional and shear wave velocities and densities of the two‐phase mixture of B2‐Fe_0.67Ni_0.06Si_0.27 and hcp‐Fe‐Ni are consistent with inner core PREM values of V_P,V_S, and ρ based on a linear mixing model with 30(5) vol % B2‐Fe_0.67Ni_0.06Si_0.27 and 70(5) vol % hcp Fe‐Ni, which corresponds to ∼3–5 wt.% Si and ∼5–12 wt.% Ni.

DOI： 10.1029/2021gl096405

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2021GL096405

A New Approach Determining a Phase Transition Boundary Strictly Following a Definition of Phase Equilibrium: An Example of the Post-Spinel Transition in Mg2SiO4 System Invited Reviewed

Takayuki Ishii, Artem Chanyshev, Tomoo Katsura

Minerals 12 ( 7 ) 820 - 820 2022.6

Authorship：Lead author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：MDPI AG

The Clapeyron slope is the slope of a phase boundary in P–T space and is essential for understanding mantle dynamics and evolution. The phase boundary is delineating instead of balancing a phase transition’s normal and reverse reactions. Many previous high pressure–temperature experiments determining the phase boundaries of major mantle minerals experienced severe problems due to instantaneous pressure increase by thermal pressure, pressure drop during heating, and sluggish transition kinetics. These complex pressure changes underestimate the transition pressure, while the sluggish kinetics require excess pressures to initiate or proceed with the transition, misinterpreting the phase stability and preventing tight bracketing of the phase boundary. Our recent study developed a novel approach to strictly determine phase stability based on the phase equilibrium definition. Here, we explain the details of this technique, using the post-spinel transition in Mg2SiO4 determined by our recent work as an example. An essential technique is to observe the change in X-ray diffraction intensity between ringwoodite and bridgmanite + periclase during the spontaneous pressure drop at a constant temperature and press load with the coexistence of both phases. This observation removes the complicated pressure change upon heating and kinetic problem, providing an accurate and precise phase boundary.

DOI： 10.3390/min12070820

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Low Thermal Conductivity of Hydrous Phase D Leads to a Self‐Preservation Effect Within a Subducting Slab Reviewed

Wen‐Pin Hsieh, Enrico Marzotto, Takayuki Ishii, Leonid Dubrovinsky, Alena A. Aslandukova, Giacomo Criniti, Yi‐Chi Tsao, Chun‐Hung Lin, Jun Tsuchiya, Eiji Ohtani

Journal of Geophysical Research: Solid Earth 127 ( 6 ) 2022.6

Structural independence of hydrogen-bond symmetrisation dynamics at extreme pressure conditions Reviewed

Thomas Meier, Florian Trybel, Saiana Khandarkhaeva, Dominique Laniel, Takayuki Ishii, Alena Aslandukova, Natalia Dubrovinskaia, Leonid Dubrovinsky

Nature Communications 13 ( 1 ) 2022.6

Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

The experimental study of hydrogen-bonds and their symmetrization under extreme conditions is predominantly driven by diffraction methods, despite challenges of localising or probing the hydrogen subsystems directly. Until recently, H-bond symmetrization has been addressed in terms of either nuclear quantum effects, spin crossovers or direct structural transitions; often leading to contradictory interpretations when combined. Here, we present high-resolution in-situ ¹H-NMR experiments in diamond anvil cells investigating a range of systems containing linear O-H ⋯ O units at pressure ranges of up to 90 GPa covering their respective H-bond symmetrization. We found pronounced minima in the pressure dependence of the NMR resonance line-widths associated with a maximum in hydrogen mobility, precursor to a localisation of hydrogen atoms. These minima, independent of the chemical environment of the O-H ⋯ O unit, can be found in a narrow range of oxygen oxygen distances between 2.44 and 2.45 Å, leading to an average critical oxygen-oxygen distance of $${\bar{r } }_{ { { { { { { { \rm{OO } } } } } } } } }^{ { { { { { { { \rm{crit } } } } } } } } }=2.443(1)$$ Å.

DOI： 10.1038/s41467-022-30662-4

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Other Link： https://www.nature.com/articles/s41467-022-30662-4

The electrical conductivity of Fe4O5, Fe5O6, and Fe7O9 up to 60 GPa Reviewed

Shuhou Maitani, Ryosuke Sinmyo, Takayuki Ishii, Saori I. Kawaguchi, Naohisa Hirao

Physics and Chemistry of Minerals 49 ( 5 ) 2022.5

Equations of state of α-SiC (6H) and βʹ-Mg2Si1.1 from single-crystal X-ray diffraction data and novel high-pressure magnesium silicide Mg2Si7 Reviewed

Iuliia Koemets, Takayuki Ishii, Michael Hanfland, Leonid Dubrovinsky

Physics and Chemistry of Minerals 49 ( 5 ) 2022.5

Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

SiC and (Fe, Mg)-silicide are candidate phases forming under reducing conditions in the Earth and planetary interiors. However, structural studies of SiC and Mg₂Si at high pressure and their thermal stability are presently lacking. In this work, we applied single-crystal X-ray diffraction in a diamond anvil cell at high pressure and determined the equations of state of α-SiC (6H) and βʹ-Mg₂Si_1.1 up to 60 and 40 GPa, respectively, yielding bulk moduli of 226.0(4) and 56(1) GPa. We also report the formation of a novel orthorhombic Mg₂Si₇ phase upon laser heating βʹ-Mg₂Si_1.1 at ~ 45 GPa and 2000 °C [Pbam, a = 7.16(1) Å, b = 12.490(3) Å, c = 2.6545(3) Å, V = 237.5(3) Å³]. The structure of this compound contains layers formed by irregular 12-member silicon rings, which are arranged in channels filled with both Mg and Si atoms. No signs of the Mg₂Si₇ phase were detected upon releasing the pressure in the DAC, which suggests that this phase is unstable under ambient conditions.

DOI： 10.1007/s00269-022-01189-3

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Other Link： https://link.springer.com/article/10.1007/s00269-022-01189-3/fulltext.html

Aluminum and hydrogen partitioning between bridgmanite and high-pressure hydrous phases: Implications for water storage in the lower mantle Reviewed

Takayuki Ishii, Eiji Ohtani, Anton Shatskiy

Earth and Planetary Science Letters 583 117441 - 117441 2022.4

High pressure-temperature phase relations of basaltic crust up to mid-mantle conditions Reviewed

Takayuki Ishii, Nobuyoshi Miyajima, Giacomo Criniti, Qingyang Hu, Konstantin Glazyrin, Tomoo Katsura

Earth and Planetary Science Letters 584 117472 - 117472 2022.4

Extreme conditions research using the large-volume press at the P61B endstation, PETRA III Reviewed

Robert Farla, Shrikant Bhat, Stefan Sonntag, Artem Chanyshev, Shuailing Ma, Takayuki Ishii, Zhaodong Liu, Adrien Néri, Norimasa Nishiyama, Guilherme Abreu Faria, Thomas Wroblewski, Horst Schulte-Schrepping, Wolfgang Drube, Oliver Seeck, Tomoo Katsura

Journal of Synchrotron Radiation 29 ( 2 ) 409 - 423 2022.2

Publishing type：Research paper (scientific journal) Publisher：International Union of Crystallography (IUCr)

Penetrating, high-energy synchrotron X-rays are in strong demand, particularly for high-pressure research in physics, chemistry and geosciences, and for materials engineering research under less extreme conditions. A new high-energy wiggler beamline P61 has been constructed to meet this need at PETRA III in Hamburg, Germany. The first part of the paper offers an overview of the beamline front-end components and beam characteristics. The second part describes the performance of the instrumentation and the latest developments at the P61B endstation. Particular attention is given to the unprecedented high-energy photon flux delivered by the ten wigglers of the PETRA III storage ring and the challenges faced in harnessing this amount of flux and heat load in the beam. Furthermore, the distinctiveness of the world's first six-ram Hall-type large-volume press, Aster-15, at a synchrotron facility is described for research with synchrotron X-rays. Additionally, detection schemes, experimental strategies and preliminary data acquired using energy-dispersive X-ray diffraction and radiography techniques are presented.

DOI： 10.1107/s1600577522001047

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Depressed 660-km discontinuity caused by akimotoite–bridgmanite transition Reviewed

Artem Chanyshev, Takayuki Ishii, Dmitry Bondar, Shrikant Bhat, Eun Jeong Kim, Robert Farla, Keisuke Nishida, Zhaodong Liu, Lin Wang, Ayano Nakajima, Bingmin Yan, Hu Tang, Zhen Chen, Yuji Higo, Yoshinori Tange, Tomoo Katsura

Nature 601 ( 7891 ) 69 - 73 2022.1

Authorship：Corresponding author Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

The 660-kilometre seismic discontinuity is the boundary between the Earth’s lower mantle and transition zone and is commonly interpreted as being due to the dissociation of ringwoodite to bridgmanite plus ferropericlase (post-spinel transition)^1–3. A distinct feature of the 660-kilometre discontinuity is its depression to 750 kilometres beneath subduction zones^4–10. However, in situ X-ray diffraction studies using multi-anvil techniques have demonstrated negative but gentle Clapeyron slopes (that is, the ratio between pressure and temperature changes) of the post-spinel transition that do not allow a significant depression^11–13. On the other hand, conventional high-pressure experiments face difficulties in accurate phase identification due to inevitable pressure changes during heating and the persistent presence of metastable phases^1,3. Here we determine the post-spinel and akimotoite–bridgmanite transition boundaries by multi-anvil experiments using in situ X-ray diffraction, with the boundaries strictly based on the definition of phase equilibrium. The post-spinel boundary has almost no temperature dependence, whereas the akimotoite–bridgmanite transition has a very steep negative boundary slope at temperatures lower than ambient mantle geotherms. The large depressions of the 660-kilometre discontinuity in cold subduction zones are thus interpreted as the akimotoite–bridgmanite transition. The steep negative boundary of the akimotoite–bridgmanite transition will cause slab stagnation (a stalling of the slab’s descent) due to significant upward buoyancy^14,15.

DOI： 10.1038/s41586-021-04157-z

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Other Link： https://www.nature.com/articles/s41586-021-04157-z

High‐Pressure Elasticity of δ‐(Al,Fe)OOH Single Crystals and Seismic Detectability of Hydrous MORB in the Shallow Lower Mantle Reviewed

Niccolò Satta, Giacomo Criniti, Alexander Kurnosov, Tiziana Boffa Ballaran, Takayuki Ishii, Hauke Marquardt

Geophysical Research Letters 48 ( 23 ) 2021.12

Synthesis of paracrystalline diamond Reviewed

Hu Tang, Xiaohong Yuan, Yong Cheng, Hongzhan Fei, Fuyang Liu, Tao Liang, Zhidan Zeng, Takayuki Ishii, Ming-Sheng Wang, Tomoo Katsura, Howard Sheng, Huiyang Gou

Nature 599 ( 7886 ) 605 - 610 2021.11

A simplified rapid-quench multi-anvil technique Reviewed

Dmitry Bondar, Hongzhan Fei, Anthony C. Withers, Takayuki Ishii, Artem Chanyshev, Tomoo Katsura

Review of Scientific Instruments 92 ( 11 ) 113902 - 113902 2021.11

Spectroscopic evidence for the Fe3+ spin transition in iron-bearing δ-AlOOH at high pressure Reviewed

Xiaowan Su, Chaoshuai Zhao, Liangxu Xu, Chaojia Lv, Xitong Song, Takayuki Ishii, Yuming Xiao, Paul Chow, Qiang Sun, Jin Liu

American Mineralogist 106 ( 11 ) 1709 - 1716 2021.11

Publishing type：Research paper (scientific journal) Publisher：Mineralogical Society of America

Abstract

δ-AlOOH has emerged as a promising candidate for water storage in the lower mantle and could have delivered water into the bottom of the mantle. To date, it still remains unclear how the presence of iron affects its elastic, rheological, vibrational, and transport properties, especially across the spin crossover. Here, we conducted high-pressure X-ray emission spectroscopy experiments on a δ-(Al0.85Fe0.15) OOH sample up to 53 GPa using silicone oil as the pressure transmitting medium in a diamond-anvil cell. We also carried out laser Raman measurements on δ-(Al0.85Fe0.15)OOH and δ-(Al0.52Fe0.48)OOH up to 57 and 62 GPa, respectively, using neon as the pressure-transmitting medium. Evolution of Raman spectra of δ-(Al0.85Fe0.15)OOH with pressure shows two new bands at 226 and 632 cm−1 at 6.0 GPa, in agreement with the transition from an ordered (P21nm) to a disordered hydrogen bonding structure (Pnnm) for δ-AlOOH. Similarly, the two new Raman bands at 155 and 539 cm−1 appear in δ-(Al0.52Fe0.48)OOH between 8.5 and 15.8 GPa, indicating that the incorporation of 48 mol% FeOOH could postpone the order-disorder transition upon compression. On the other hand, the satellite peak (Kβ′) intensity of δ-(Al0.85Fe0.15)OOH starts to decrease at ~30 GPa and it disappears completely at 42 GPa. That is, δ-(Al0.85Fe0.15)OOH undergoes a gradual electronic spin-pairing transition at 30–42 GPa. Furthermore, the pressure dependence of Raman shifts of δ-(Al0.85Fe0.15)OOH discontinuously decreases at 32–37 GPa, suggesting that the improved hydrostaticity by the use of neon pressure medium could lead to a relatively narrow spin crossover. Notably, the pressure dependence of Raman shifts and optical color of δ-(Al0.52Fe0.48)OOH dramatically change at 41–45 GPa, suggesting that it probably undergoes a relatively sharp spin transition in the neon pressure medium. Together with literature data on the solid solutions between δ-AlOOH and ε-FeOOH, we found that the onset pressure of the spin transition in δ-(Al,Fe)OOH increases with increasing FeOOH content. These results shed new insights into the effects of iron on the structural evolution and vibrational properties of δ-AlOOH. The presence of FeOOH in δ-AlOOH can substantially influence its high-pressure behavior and stability at the deep mantle conditions and play an important role in the deep-water cycle.

DOI： 10.2138/am-2021-7541

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In situ high-pressure nuclear magnetic resonance crystallography in one and two dimensions Reviewed

Thomas Meier, Alena Aslandukova, Florian Trybel, Dominique Laniel, Takayuki Ishii, Saiana Khandarkhaeva, Natalia Dubrovinskaia, Leonid Dubrovinsky

Matter and Radiation at Extremes 6 ( 6 ) 068402 - 068402 2021.11

The elastic properties and anisotropic behavior of MgSiO3 akimotoite at transition zone pressures Reviewed

Nicki C. Siersch, Alexander Kurnosov, Giacomo Criniti, Takayuki Ishii, Tiziana Boffa Ballaran, Daniel J. Frost

Physics of the Earth and Planetary Interiors 320 106786 - 106786 2021.11

Simultaneous generation of ultrahigh pressure and temperature to 50 GPa and 3300 K in multi-anvil apparatus Reviewed

Longjian Xie, Artem Chanyshev, Takayuki Ishii, Dmitry Bondar, Keisuke Nishida, Zhen Chen, Shrikant Bhat, Robert Farla, Yuji Higo, Yoshinori Tange, Xiaowan Su, BingMin Yan, Shuailin Ma, Tomoo Katsura

Review of Scientific Instruments 92 ( 10 ) 103902 - 103902 2021.10

Determination of phase relations of the olivine–ahrensite transition in the Mg2SiO4–Fe2SiO4 system at 1740 K using modern multi-anvil techniques Reviewed

Artem Chanyshev, Dmitry Bondar, Hongzhan Fei, Narangoo Purevjav, Takayuki Ishii, Keisuke Nishida, Shrikant Bhat, Robert Farla, Tomoo Katsura

Contributions to Mineralogy and Petrology 176 ( 10 ) 2021.9

Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

The phase relations of iron-rich olivine and its high-pressure polymorphs are important for planetary science and meteoritics because these minerals are the main constituents of terrestrial mantles and meteorites. The olivine–ahrensite binary loop was previously determined by thermochemical calculations in combination with high-pressure experiments; however, the transition pressures contained significant uncertainties. Here we determined the binary loop of the olivine–ahrensite transition in the (Mg,Fe)₂SiO₄ system at 1740 K in the pressure range of 7.5–11.2 GPa using a multi-anvil apparatus with the pressure determined using in situ X-ray diffraction, compositional analysis of quenched run products, and thermochemical calculation. Based on the determined binary loop, a user-friendly software was developed to calculate pressure from the coexisting olivine and ahrensite compositions. The software is used to estimate the shock conditions of several L6-type chondrites. The obtained olivine–ahrensite phase relations can also be applied for precise in-house multi-anvil pressure calibration at high temperatures.

DOI： 10.1007/s00410-021-01829-x

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Other Link： https://link.springer.com/article/10.1007/s00410-021-01829-x/fulltext.html

Vibrational anisotropy of δ-(Al,Fe)OOH single crystals as probed by nuclear resonant inelastic X-ray scattering Reviewed

Johannes Buchen, Wolfgang Sturhahn, Takayuki Ishii, Jennifer M. Jackson

European Journal of Mineralogy 33 ( 4 ) 485 - 502 2021.8

Publishing type：Research paper (scientific journal) Publisher：Copernicus GmbH

Abstract. The formation of high-pressure oxyhydroxide phases spanned by the components AlOOH–FeOOH–MgSiO2(OH)2 in experiments suggests their capability to retain hydrogen in Earth's lower mantle. Understanding the vibrational properties of high-pressure phases provides the basis for assessing their thermal properties, which are required to compute phase diagrams and physical properties. Vibrational properties can be highly anisotropic, in particular for materials with crystal structures of low symmetry that contain directed structural groups or components. We used nuclear resonant inelastic X-ray scattering (NRIXS) to probe lattice vibrations that involve motions of 57Fe atoms in δ-(Al0.87Fe0.13)OOH single crystals. From the recorded single-crystal NRIXS spectra, we calculated projections of the partial phonon density of states along different crystallographic directions. To describe the anisotropy of central vibrational properties, we define and derive tensors for the partial phonon density of states, the Lamb–Mössbauer factor, the mean kinetic energy per vibrational mode, and the mean force constant of 57Fe atoms. We further show how the anisotropy of the Lamb–Mössbauer factor can be translated into anisotropic displacement parameters for 57Fe atoms and relate our findings on vibrational anisotropy to the crystal structure of δ-(Al,Fe)OOH. As a potential application of single-crystal NRIXS at high pressures, we discuss the evaluation of anisotropic thermal stresses in the context of elastic geobarometry for mineral inclusions. Our results on single crystals of δ-(Al,Fe)OOH demonstrate the sensitivity of NRIXS to vibrational anisotropy and provide an in-depth description of the vibrational behavior of Fe3+ cations in a crystal structure that may motivate future applications of NRIXS to study anisotropic vibrational properties of minerals.

DOI： 10.5194/ejm-33-485-2021

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P-V-Tmeasurements of Fe3C to 117 GPa and 2100 K: Implications for stability of Fe3C phase at core conditions Reviewed

Chris McGuire, Tetsuya Komabayashi, Samuel Thompson, Geoffrey Bromiley, Takayuki Ishii, Eran Greenberg, Vitali B. Prakapenka

American Mineralogist 106 ( 8 ) 1349 - 1359 2021.8

Publishing type：Research paper (scientific journal) Publisher：Mineralogical Society of America

Abstract

We report the thermal Equation of State (EoS) of the non-magnetic Fe3C phase based on in situ X-ray diffraction (XRD) experiments to 117 GPa and 2100 K. High-pressure and temperature unit-cell volume measurements of Fe3C were conducted in a laser-heated diamond-anvil cell. Our pressure-volume-temperature (P-V-T) data together with existing data were fit to the Vinet equation of state with the Mie-Grüneisen-Debye thermal pressure model, yielding V0 = 151.6(12) Å3, K0 = 232(24) GPa, K0′= 5.09(46), γ0 = 2.3(3), and q = 3.4 (9) with θ0 = 407 K (fixed). The high-T data were also fit to the thermal pressure model with a constant αKT term, PTh = αKT(ΔT), and there is no observable pressure or temperature dependence, which implies minor contributions from the anharmonic and electronic terms. Using the established EoS for Fe3C, we made thermodynamic calculations on the P-T locations of the breakdown reaction of Fe3C into Fe7C3 and Fe. The reaction is located at 87 GPa and 300 K and 251 GPa and 3000 K. An invariant point occurs where Fe, Fe3C, Fe7C3, and liquid are stable, which places constraints on the liquidus temperature of the outer core, namely inner core crystallization temperature, as the inner core would be comprised by the liquidus phase. Two possible P-T locations for the invariant point were predicted from existing experimental data and the reaction calculated in this study. The two models result in different liquidus “phases” at the outer core-inner core boundary pressure: Fe3C at 5300 K and Fe7C3 at 3700 K. The Fe7C3 inner core can account for the density, as observed by seismology, while the Fe3C inner core cannot. The relevance of the system Fe-C to Earth’s core can be resolved by constructing a thermodynamic model for melting relations under core conditions as the two models predict very different liquidus temperatures.

DOI： 10.2138/am-2021-7581

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High-pressure syntheses and crystal structure analyses of a new low-density CaFe2O4-related and CaTi2O4-type MgAl2O4 phases Reviewed

Takayuki Ishii, Giacomo Criniti, Elena Bykova, Leonid Dubrovinsky, Tomoo Katsura, Hidekazu Arii, Hiroshi Kojitani, Masaki Akaogi

American Mineralogist 106 ( 7 ) 1105 - 1112 2021.7

Authorship：Lead author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：Mineralogical Society of America

Abstract

Three single crystals of CaTi2O4 (CT)-type, CaFe2O4 (CF)-type, and new low-density CaFe2O4 (LD-CF) related MgAl2O4 were synthesized at 27 GPa and 2500 °C and also CT-type MgAl2O4 at 45 GPa and 1727 °C using conventional and advanced multi-anvil technologies, respectively. The structures of CT-type and LD-CF related MgAl2O4 were analyzed by single-crystal X-ray diffraction. The lattice parameters of the CT-type phases synthesized at 27 and 45 GPa were a = 2.7903(4), b = 9.2132(10), and c = 9.3968(12) Å, and a = 2.7982(6), b = 9.2532(15), and c = 9.4461(16) Å, respectively, (Z = 4, space group: Cmcm) at ambient conditions. This phase has an AlO6 octahedral site and an MgO8 bicapped trigonal prism with two longer cation-oxygen bonds. The LD-CF related phase has a novel structure with orthorhombic symmetry (space group: Pnma), and lattice parameters of a = 9.207(2), b = 3.0118(6), and c = 9.739(2) Å (Z = 4). The structural framework comprises tunnel-shaped spaces constructed by edge- and corner-sharing of AlO6 and a 4+1 AlO5 trigonal bipyramid, in which MgO5 trigonal bipyramids are accommodated. The CF-type MgAl2O4 also has the same space group of Pnma but a slightly different atomic arrangement, with Mg and Al coordination numbers of 8 and 6, respectively. The LD-CF related phase has the lowest density of 3.50 g/cm3 among MgAl2O4 polymorphs, despite its high-pressure synthesis from the spinel-type phase (3.58 g/cm3), indicating that the LD-CF related phase formed via back-transformation from a high-pressure phase during the recovery. Combined with the previously determined phase relations, the phase transition between CF-and CT-type MgAl2O4 is expected to have a steep Clapeyron slope. Therefore, CT-type phase may be stable in basaltic- and continental-crust compositions at higher temperatures than the average mantle geotherm in the wide pressure range of the lower mantle. The LD-CF related phase could be found in shocked meteorites and used for estimating shock conditions.

DOI： 10.2138/am-2021-7619

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Dry metastable olivine and slab deformation in a wet subducting slab Reviewed

Takayuki Ishii, Eiji Ohtani

Nature Geoscience 14 ( 7 ) 526 - 530 2021.5

Effect of Water on Lattice Thermal Conductivity of Ringwoodite and Its Implications for the Thermal Evolution of Descending Slabs Reviewed

Enrico Marzotto, Wen‐Pin Hsieh, Takayuki Ishii, Keng‐Hsien Chao, Gregor J. Golabek, Marcel Thielmann, Eiji Ohtani

Geophysical Research Letters 47 ( 13 ) 2020.7

Discovery of New‐Structured Post‐Spinel MgFe ₂ O ₄ : Crystal Structure and High‐Pressure Phase Relations Reviewed

Takayuki Ishii, Nobuyoshi Miyajima, Ryosuke Sinmyo, Hiroshi Kojitani, Daisuke Mori, Yoshiyuki Inaguma, Masaki Akaogi

Geophysical Research Letters 47 ( 6 ) 2020.3

Spin Transition of Iron in δ‐(Al,Fe)OOH Induces Thermal Anomalies in Earth's Lower Mantle Reviewed

Wen‐Pin Hsieh, Takayuki Ishii, Keng‐Hsien Chao, Jun Tsuchiya, Frédéric Deschamps, Eiji Ohtani

Geophysical Research Letters 47 ( 4 ) 2020.2

Stability and Solubility of the FeAlO ₃ Component in Bridgmanite at Uppermost Lower Mantle Conditions Reviewed

Zhaodong Liu, Catherine McCammon, Biao Wang, Leonid Dubrovinsky, Takayuki Ishii, Dmitry Bondar, Ayano Nakajima, Yoshinori Tange, Yuji Higo, Tian Cui, Bingbing Liu, Tomoo Katsura

Journal of Geophysical Research: Solid Earth 125 ( 2 ) 2020.2

Development of High-Pressure Technology with Kawai-Type Multi-Anvil Presses and its Application to Geoscience Invited Reviewed

Takayuki ISHII

The Review of High Pressure Science and Technology 30 ( 2 ) 156 - 165 2020

Crystal Structure of a Novel Fe-Mg Oxide and Deep Earth Science Invited Reviewed

Takayuki ISHII

Nihon Kessho Gakkaishi 61 ( 4 ) 205 - 206 2019.12

Sharp 660-km discontinuity controlled by extremely narrow binary post-spinel transition Reviewed

Takayuki Ishii, Rong Huang, Robert Myhill, Hongzhan Fei, Iuliia Koemets, Zhaodong Liu, Fumiya Maeda, Liang Yuan, Lin Wang, Dmitry Druzhbin, Takafumi Yamamoto, Shrikant Bhat, Robert Farla, Takaaki Kawazoe, Noriyoshi Tsujino, Eleonora Kulik, Yuji Higo, Yoshinori Tange, Tomoo Katsura

Nature Geoscience 12 ( 10 ) 869 - 872 2019.9

The stability of Fe5O6 and Fe4O5 at high pressure and temperature Reviewed

Koutaro Hikosaka, Ryosuke Sinmyo, Kei Hirose, Takayuki Ishii, Yasuo Ohishi

American Mineralogist 104 ( 9 ) 1356 - 1359 2019.9

A Breakthrough in Pressure Generation by a Kawai-Type Multi-Anvil Apparatus with Tungsten Carbide Anvils Invited Reviewed

Takayuki Ishii, Zhaodong Liu, Tomoo Katsura

Engineering 5 ( 3 ) 434 - 440 2019.6

Phase Relations of Harzburgite and MORB up to the Uppermost Lower Mantle Conditions: Precise Comparison With Pyrolite by Multisample Cell High‐Pressure Experiments With Implication to Dynamics of Subducted Slabs Reviewed

Takayuki Ishii, Hiroshi Kojitani, Masaki Akaogi

Journal of Geophysical Research: Solid Earth 124 ( 4 ) 3491 - 3507 2019.4

High-Pressure Phase Relations and Crystal Structures of Postspinel Phases in MgV₂O₄, FeV₂O₄, and MnCr₂O₄: Crystal Chemistry of AB₂O₄ Postspinel Compounds Reviewed

Takayuki Ishii, Tsubasa Sakai, Hiroshi Kojitani, Daisuke Mori, Yoshiyuki Inaguma, Yoshitaka Matsushita, Kazunari Yamaura, Masaki Akaogi

Inorganic Chemistry 57 ( 11 ) 6648 - 6657 2018.5

Complete agreement of the post-spinel transition with the 660-km seismic discontinuity Reviewed

Takayuki Ishii, Rong Huang, Hongzhan Fei, Iuliia Koemets, Zhaodong Liu, Fumiya Maeda, Liang Yuan, Lin Wang, Dmitry Druzhbin, Takafumi Yamamoto, Shrikant Bhat, Robert Farla, Takaaki Kawazoe, Noriyoshi Tsujino, Eleonora Kulik, Yuji Higo, Yoshinori Tange, Tomoo Katsura

Scientific Reports 8 ( 1 ) 2018.4

High-pressure phase transitions in MgCr2O4·Mg2SiO4 composition: Reactions between olivine and chromite with implications for ultrahigh-pressure chromitites Reviewed

Masaki Akaogi, Airi Kawahara, Hiroshi Kojitani, Kazuaki Yoshida, Yuki Anegawa, Takayuki Ishii

American Mineralogist 103 ( 1 ) 161 - 170 2018.1

Phase relations and mineral chemistry in pyrolitic mantle at 1600–2200 °C under pressures up to the uppermost lower mantle: Phase transitions around the 660-km discontinuity and dynamics of upwelling hot plumes Reviewed

Takayuki Ishii, Hiroshi Kojitani, Masaki Akaogi

Physics of the Earth and Planetary Interiors 274 127 - 137 2018.1

Synthesis and crystal structure of Mg-bearing Fe9O11: New insight in the complexity of Fe-Mg oxides at conditions of the deep upper mantle Reviewed

American Mineralogist 2018

Phase Relations in the System MgSiO₃ -Al₂ O₃ up to 2300 K at Lower Mantle Pressures Reviewed

Zhaodong Liu, Masayuki Nishi, Takayuki Ishii, Hongzhan Fei, Nobuyoshi Miyajima, Tiziana Boffa Ballaran, Hiroaki Ohfuji, Takeshi Sakai, Lin Wang, Svyatoslav Shcheka, Takeshi Arimoto, Yoshinori Tange, Yuji Higo, Tetsuo Irifune, Tomoo Katsura

Journal of Geophysical Research: Solid Earth 122 ( 10 ) 7775 - 7788 2017.10

A shallow origin of so-called ultrahigh-pressure chromitites, based on single-crystal X-ray structure analysis of the high-pressure Mg₂Cr₂O₅ phase, with modified ludwigite-type structure Reviewed

Takayuki Ishii, Noriyoshi Tsujino, Hidekazu Arii, Kiyoshi Fujino, Nobuyoshi Miyajima, Hiroshi Kojitani, Takehiro Kunimoto, Masaki Akaogi

American Mineralogist 102 ( 10 ) 2113 - 2118 2017.10

Rapid decrease of MgAlO2.5 component in bridgmanite with pressure Reviewed

Z. Liu, T. Ishii, T. Katsura

Geochemical Perspectives Letters 12 - 18 2017.10

Pressure generation to 65 GPa in a Kawai-type multi-anvil apparatus with tungsten carbide anvils Reviewed

Takayuki Ishii, Daisuke Yamazaki, Noriyoshi Tsujino, Fang Xu, Zhaodong Liu, Takaaki Kawazoe, Takafumi Yamamoto, Dmitry Druzhbin, Lin Wang, Yuji Higo, Yoshinori Tange, Takashi Yoshino, Tomoo Katsura

High Pressure Research 37 ( 4 ) 507 - 515 2017.9

Single crystal synthesis of δ-(Al,Fe)OOH Reviewed

Takaaki Kawazoe, Itaru Ohira, Takayuki Ishii, Tiziana Boffa Ballaran, Catherine McCammon, Akio Suzuki, Eiji Ohtani

American Mineralogist 102 ( 9 ) 1953 - 1956 2017.9

Synthesis and crystal structure of LiNbO₃-type Mg₃Al₂Si₃O₁₂: A possible indicator of shock conditions of meteorites Reviewed

Takayuki Ishii, Ryosuke Sinmyo, Tetsuya Komabayashi, Tiziana Boffa Ballaran, Takaaki Kawazoe, Nobuyoshi Miyajima, Kei Hirose, Tomoo Katsura

American Mineralogist 102 ( 9 ) 1947 - 1952 2017.9

Shocked chromites in fossil L chondrites: A Raman spectroscopy and transmission electron microscopy study Reviewed

Surya S. Rout, Philipp R. Heck, Nestor J. Zaluzec, Takayuki Ishii, Jianguo Wen, Dean J. Miller, Birger Schmitz

Meteoritics & Planetary Science 52 ( 9 ) 1776 - 1796 2017.5

High-pressure high-temperature phase relations in FeTiO3 up to 35 GPa and 1600 °C Reviewed

M. Akaogi, K. Abe, H. Yusa, T. Ishii, T. Tajima, H. Kojitani, D. Mori, Y. Inaguma

Physics and Chemistry of Minerals 44 ( 1 ) 63 - 73 2016.8

Generation of pressures over 40 GPa using Kawai-type multi-anvil press with tungsten carbide anvils Reviewed

D. Druzhbin, R. Myhill

Review of Scientific Instruments 87 ( 2 ) 024501 - 024501 2016.2

High-pressure high-temperature transitions in MgCr2O4 and crystal structures of new Mg2Cr2O5 and post-spinel MgCr2O4 phases with implications for ultrahigh-pressure chromitites in ophiolites Reviewed

T. Ishii, H. Kojitani, K. Fujino, H. Yusa, D. Mori, Y. Inaguma, Y. Matsushita, K. Yamaura, M. Akaogi

American Mineralogist 100 ( 1 ) 59 - 65 2015.1

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

T. Ishii, H. Kojitani, S. Tsukamoto, K. Fujino, D. Mori, Y. Inaguma, N. Tsujino, T. Yoshino, D. Yamazaki, Y. Higo, K. Funakoshi, M. Akaogi

American Mineralogist 99 ( 8-9 ) 1788 - 1797 2014.8

High-pressure synthesis of the BaIrO3 perovskite: A Pauli paramagnetic metal with a Fermi liquid ground state Reviewed

J.-G. Cheng, T. Ishii, H. Kojitani, K. Matsubayashi, A. Matsuo, X. Li, Y. Shirako, J.-S. Zhou, J. B. Goodenough, C. Q. Jin, M. Akaogi, Y. Uwatoko

Physical Review B 88 ( 20 ) 2013.11

High-pressure phase transitions and subduction behavior of continental crust at pressure–temperature conditions up to the upper part of the lower mantle Reviewed

Takayuki Ishii, Hiroshi Kojitani, Masaki Akaogi

Earth and Planetary Science Letters 357-358 31 - 41 2012.12

Thermodynamic investigation on phase equilibrium boundary between calcium ferrite-type MgAl2O4 and MgO+α-Al2O3 Reviewed

Hiroshi Kojitani, Takayuki Ishii, Masaki Akaogi

Physics of the Earth and Planetary Interiors 212-213 100 - 105 2012.12

High-pressure phase relations in the system TiO2–ZrO2 to 12 GPa: stability of αPbO2-type srilankite solid solutions of (Ti1−x , Zr x )O2 (0 ≤ x ≤ 0.6) Reviewed

Masaki Akaogi, Nanami Horiuchi, Takayuki Ishii, Hiroshi Kojitani

Physics and Chemistry of Minerals 39 ( 10 ) 797 - 802 2012.8

Post-spinel transitions in pyrolite and Mg2SiO4 and akimotoite–perovskite transition in MgSiO3: Precise comparison by high-pressure high-temperature experiments with multi-sample cell technique Reviewed

Takayuki Ishii, Hiroshi Kojitani, Masaki Akaogi

Earth and Planetary Science Letters 309 ( 3-4 ) 185 - 197 2011.9

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