掲載種別：研究論文（学術雑誌）  

Pressure-induced transformations in glassy GeSe2 have been studied using the x-ray absorption spectroscopy. Experiments have been carried out at the scanning-energy beamline BM23 (European Synchrotron Radiation Facility) providing a micrometric x-ray focal spot up to pressures of about 45 GPa in a diamond anvil cell. Both Se and Ge K-edge experiments were performed under different hydrostatic conditions identifying the metallization onsets by accurate determinations of the edge shifts. The semiconductor-metal transition was observed to be completed around 20 GPa when neon was used as a pressure transmitting medium (PTM), while this transition was slightly shifted to lower pressures when no PTM was used. Accurate double-edge extended x-ray absorption fine structure (EXAFS) refinements were carried out using advanced data-analysis methods. EXAFS data-analysis confirmed the trend shown by the edge shifts for this disordered material, showing that the transition from tetrahedral to octahedral coordination for Ge sites is not fully achieved at 45 GPa. Results of present high pressure EXAFS experiments have shown the absence of significant neon incorporation into the glass within the pressure range up to 45 GPa.

DOI： 10.1088/1361-648X/acc8b1

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掲載種別：研究論文（学術雑誌）  

Ice polymorphs show extraordinary structural diversity depending on pressure and temperature. The behavior of hydrogen-bond disorder not only is a key ingredient for their structural diversity but also controls their physical properties. However, it has been a challenge to determine the details of the disordered structure in ice polymorphs under pressure, because of the limited observable reciprocal space and inaccuracies related to high-pressure techniques. Here, we present an elucidation of the disordered structure of ice VII, the dominant high-pressure form of water, at 2.2 GPa and 298 K, from both single-crystal and powder neutron-diffraction techniques. We reveal the three-dimensional atomic distributions from the maximum entropy method and unexpectedly find a ring-like distribution of hydrogen in contrast to the commonly accepted discrete sites. In addition, total scattering analysis at 274 K clarified the difference in the intermolecular structure from ice VIII, the ordered counterpart of ice VII, despite an identical molecular geometry. Our complementary structure analyses robustly demonstrate the unique disordered structure of ice VII. Furthermore, these findings are related to proton dynamics, which drastically vary with pressure, and will contribute to an understanding of the structural origin of anomalous physical properties of ice VII under pressures.

DOI： 10.1073/pnas.2208717119

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-V C H VERLAG GMBH  

The structure of the Ga85.8In14.2 eutectic liquid alloy is investigated both under ambient conditions and at high pressure/high temperature using X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques. The local structure of the liquid alloy at ambient conditions is analyzed using double-edge refinements of the XAS data. Solid-liquid phase transitions under high-pressure and high-temperature conditions are monitored by combined XAS and XRD measurements along several quasi-isobaric heating runs, allowing to draw a melting line up to 10 GPa. The established melting line is found to be slightly below the one of pure gallium (Ga) and to follow its trend as expected from the eutectic nature of the compound. A series of Ga K-edge X-ray absorption fine structure (XAFS) spectra measured at different pressures indicates the absence of large structural modifications at local Ga sites in the liquid within the investigated pressure and temperature range.

DOI： 10.1002/pssr.202100423

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

Single-crystal neutron diffraction provides direct information about crystal structures such as hydrogen positions and magnetic structures. However, in-situ experiments conducted under high pressure entail technical difficulties such as attenuation correction, masking of parasitic diffraction, and limitations of sample volumes and accessible directions. For this study, we improved diamond anvil cells with a tubular frame made of Zr-based bulk metallic glass and nano-polycrystalline diamond anvils for single-crystal neutron diffraction. The thicker tubular frame was confirmed through experimentation as stably generating 4.5 GPa. Its feasibility for neutron diffraction was assessed at the Laue-TOF diffractometer at the BL18 (SENJU) beamline in the MLF J-PARC using time-resolved two-dimensional detectors covering wide solid angles. In addition to ambient-pressure measurements of NH4Cl, diffraction patterns of a high-pressure phase of ice were also collected in-situ. The obtained intensities are of refinable quality sufficient for structure analysis.

DOI： 10.1080/08957959.2022.2045982

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掲載種別：研究論文（学術雑誌）  

Cu2IrO3 is among the newest layered honeycomb iridates and a promising candidate to harbor a Kitaev quantum spin liquid state. Here, we investigate the pressure and temperature dependence of its structure through a combination of powder x-ray diffraction and x-ray absorption fine structure measurements, as well as ab initio evolutionary structure search. At ambient pressure, we revise the previously proposed C2/c solution with a related but notably more stable P21/c structure. Pressures below 8 GPa drive the formation of Ir-Ir dimers at both ambient and low temperatures, similar to the case of Li2IrO3. At higher pressures, the structural evolution dramatically depends on temperature. A large discontinuous reduction of the Ir honeycomb interplanar distance is observed around 15 GPa at room temperature, likely driven by a collapse of the O-Cu-O dumbbell bonds. At 15 K, pressures beyond 20 GPa first lead to an intermediate phase featuring a continuous reduction of the interplanar distance, which then collapses at 30 GPa across yet another phase transition. However, the resulting structure around 40 GPa is not the same at room and low temperatures. Remarkably, the reduction in interplanar distance leads to an apparent healing of the stacking faults at room temperature, but not at 15 K. Possible implications on the evolution of electronic structure of Cu2IrO3 with pressure are discussed.

DOI： 10.1103/PhysRevB.104.014102

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掲載種別：研究論文（学術雑誌）  

As-cast Mg97Zn1Y2 alloy consists of α-Mg matrix and 18R-type long-period stacking-ordered (LPSO) structures. We observed that the alloy undergoes a phase transformation to D03 superlattices and α-Mg matrix due to high-pressure high-temperature (HPHT) annealing at 3 GPa and above 773 K. Further, the alloy recovered after HPHT annealing, consisting of the α-Mg matrix and D03 superlattices, transformed into 18R-type LPSO structures during further annealing at ambient pressure. An fcc structure with a lattice parameter of 1.42 nm, which was twice that of D03, emerged in both the collapse process of the 18R-type LPSO structure under high-pressure, and the formation process of the 18R-type LPSO structure at ambient pressure. This fcc phase was an intermediate structure between 18R-type LPSO and D03 . From the electron diffraction results, it is considered that 18R-type LPSO is continuously present with 2H including stacking faults, which almost corresponded with previous studies.

DOI： 10.3390/met11071031

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

Bulk nanopolycrystalline diamond (NPD) samples were deformed plastically within the diamond stability field up to 14 GPa and above 1473 K. Macroscopic differential stress Delta sigma was determined on the basis of the distortion of the 111 Debye ring using synchrotron X-ray diffraction. Up to similar to 5(2)% strain, Debye ring distortion can be satisfactorily described by lattice strain theories as an ellipse. Beyond similar to 5(2)% strain, lattice spacing d(111) along the Delta sigma direction becomes saturated and remains constant with further deformation. Transmission electron microscopy on as-synthesized NPD shows well-bonded grain boundaries with no free dislocations within the grains. Deformed samples also contain very few free dislocations, while density of {111} twins increases with plastic strain. Individual grains display complex contrast, exhibiting increasing misorientation with deformation according electron diffraction. Thus, NPD does not deform by dislocation slip, which is the dominated mechanism in conventional polycrystalline diamond composites (PCDCs, grain size >1 mu m). The nonelliptical Debye ring distortion is modeled by nucleating 1/2(110) dislocations or their dissociated 1/6(112) partials gliding in the {111} planes to produce deformation twinning. With increasing strain up to , similar to 5(2)%, strength increases rapidly to , similar to 20(1) GPa, where d(111) reaches saturation. Strength beyond the saturation shows a weak dependence on strain, reaching similar to 22(1) GPa at >10% strain. Overall, the strength is similar to 2-3 times that of conventional PCDCs. Combined with molecular dynamics simulations and lattice rotation theory, we conclude that the rapid rise of strength with strain is due to defect-source strengthening, whereas further deformation is dominated by nanotwinning and lattice rotation.

DOI： 10.1021/acsnano.0c08737

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掲載種別：研究論文（学術雑誌）  

Herein we report a high temperature and high pressure driven crystallization of two-dimensional graphene oxide (GO) nanosheets to three-dimensional diamond. The successful phase transformation was confirmed using X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The phase transition platform will available to utilize for a wide variety of diamond doping employing, for example, nitrogen or other light elements, in which the correspondingly doped GO is used as the starting material.

DOI： 10.1002/slct.202100574

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掲載種別：研究論文（学術雑誌）  

We investigate the activation of Sn-V centers in diamond through ions implantation and the subsequent high pressure and high temperature (HPHT) treatment at 15 GPa and 2300 °C. Sn ions is implanted at fluences greater than 2 × 10 cm by varying the acceleration voltage up to 180 kV, which results in a Sn distribution with a uniform concentration of 1 × 10 cm down to a depth of 50 nm from the surface. The subsequent HPHT treatment recovers the transparent appearance and preserves the introduced Sn ions. The sample shows emission peaks composed of four levels that originate from the Sn-V centers. The two distinct emission peaks from the lower excited states to the split ground states are stable up to 77 K. At 10 K, these peaks are clearly observable at excitation powers spanning two orders of magnitude, which suggests the preferential carrier capture at these centers. 14 −2 20 −3

DOI： 10.35848/1347-4065/abdc31

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掲載種別：研究論文（学術雑誌）  

Metallization and dissociation are key transformations in diatomic molecules at high densities particularly significant for modeling giant planets. Using X-ray absorption spectroscopy and atomistic modeling, we demonstrate that in halogens, the formation of a connected molecular structure takes place at pressures well below metallization. Here we show that the iodine diatomic molecule first elongates by ∼0.007 Å up to a critical pressure ofP ∼ 7 GPa, developing bonds between molecules. Then its length continuously decreases with pressure up to 15-20 GPa. Universal trends in halogens are shown and allow us to predict for chlorine a pressure of 42 ± 8 GPa for molecular bond-length reversal. Our findings contribute to tackling the molecule invariability paradigm in diatomic molecular phases at high pressures and may be generalized to other abundant diatomic molecules in the universe, including hydrogen. c

DOI： 10.1039/d0cp05942k

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掲載種別：研究論文（国際会議プロシーディングス）  

The study of the applicability of a nano-polycrystalline diamond (NPD) as a lens material is presented. Two NPD plates with a diameter of 8 mm and a thickness of 0.1 and 1 mm were manufactured using the HPHT process. Coherence preservation properties of the NPD samples were checked using in-line phase-contrast imaging. Wide-Angle X-ray Scattering and Small Angle X-ray Scattering experiments were performed to examine the NPD scattering properties. Rotationally parabolic half-lens from a 100 μm thick NPD plate was manufactured using the maskless direct milling using a Zeiss CrossBeam 540 FIB-SEM system.

DOI： 10.1117/12.2594675

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掲載種別：研究論文（学術雑誌）  

© 2020 the Owner Societies. The electronic and local structural properties of CuO under pressure have been investigated by means of X-ray absorption spectroscopy (XAS) at Cu K edge and ab initio calculations, up to 17 GPa. The crystal structure of CuO consists of Cu motifs within CuO4 square planar units and two elongated apical Cu-O bonds. The CuO4 square planar units are stable in the studied pressure range, with Cu-O distances that are approximately constant up to 5 GPa, and then decrease slightly up to 17 GPa. In contrast, the elongated Cu-O apical distances decrease continuously with pressure in the studied range. An anomalous increase of the mean square relative displacement (EXAFS Debye-Waller, σ2) of the elongated Cu-O path is observed from 5 GPa up to 13 GPa, when a drastic reduction takes place in σ2. This is interpreted in terms of local dynamic disorder along the apical Cu-O path. At higher pressures (P > 13 GPa), the local structure of Cu2+ changes from a 4-fold square planar to a 4+2 Jahn-Teller distorted octahedral ion. We interpret these results in terms of the tendency of the Cu2+ ion to form favorable interactions with the apical O atoms. Also, the decrease in Cu-O apical distance caused by compression softens the normal mode associated with the out-of-plane Cu movement. CuO is predicted to have an anomalous rise in permittivity with pressure as well as modest piezoelectricity in the 5-13 GPa pressure range. In addition, the near edge features in our XAS experiment show a discontinuity and a change of tendency at 5 GPa. For P < 5 GPa the evolution of the edge shoulder is ascribed to purely electronic effects which also affect the charge transfer integral. This is linked to a charge migration from the Cu to O, but also to an increase of the energy band gap, which show a change of tendency occurring also at 5 GPa.

DOI： 10.1039/d0cp04878j

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

We have studied the amorphization process of SnI4 up to 26.8 GPa with unprecedented experimental details by combining Sn and I K-edge x-ray absorption spectroscopy and powder x-ray diffraction. Standard and reverse Monte Carlo extended x-ray absorption fine structure (EXAFS) refinements confirm that the penta atomic SnI4 structural unit tetrahedron is a fundamental structural unit that appears preserved through the crystalline phase-I to crystalline phase-II transition that has been previously reported between 7 GPa and 10 GPa. Up to now, unexploited iodine EXAFS reveals to be extremely informative and confirms the progressive formation of iodine-iodine short bonds close to 2.85 angstrom. A coordination number increase of Sn in the crystalline phase-II region appears to be excluded, while the deformation of the tetrahedral units proceeds through a flattening that keeps the average I-Sn-I angle close to 109.5 degrees. Moreover, we put in evidence the impact of pressure on the Sn near edge structure under competing geometrical and electronic effects.

DOI： 10.1063/5.0012802

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

Nitrogen is a crucial volatile element in the early Earth's evolution and the origin of life. Despite its importance, nitrogen's behavior in the Earth's interior remains poorly understood. Compared to other volatile elements, nitrogen is depleted in the Earth's atmosphere (the so-called "missing nitrogen"), calling for a hidden deep reservoir. To investigate nitrogen's behavior in the deep Earth including how the reservoir formed, high-pressure and high-temperature experiments were conducted at 28 GPa and 1,400-1,700 degrees C. To reproduce the conditions in the lower mantle, the redox was controlled using a Fe-FeO buffer. We observed that depending on the temperature conditions, stishovite can incorporate up to 90-404 ppm nitrogen, experimentally demonstrating that stishovite has the highest nitrogen solubility among the deep mantle minerals. Stishovite is the main mineral component of subducted nitrogen-rich sedimentary rocks and eroded continental crust that are eventually transported down to the lower mantle. Our results suggest that nitrogen could have been continuously transported into the lower mantle via subduction, ever since plate tectonics began.

DOI： 10.1038/s41598-020-67621-2

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

DOI： 10.1103/physrevmaterials.4.055002

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その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevMaterials.4.055002/fulltext

担当区分：最終著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. Nano-polycrystalline diamond (NPD) with various grain sizes has been synthesized from glassy carbon at pressures 15–25 GPa and temperatures 1700–2300°C using multianvil apparatus. The minimum temperature for the synthesis of pure NPD, below which a small amount of compressed graphite was formed, significantly increased with pressure from ∼1700°C at 15 GPa to ∼1900°C at 25 GPa. The NPD having grain sizes less than ∼50 nm was synthesized at temperatures below ∼2000°C at 15 GPa and ∼2300°C at 25 GPa, above which significant grain growth was observed. The grain size of NPD decreases with increasing pressure and decreasing temperature, and the pure NPD with grain sizes less than 10 nm is obtained in a limited temperature range around 1800–2000°C, depending on pressure. The pure NPD from glassy carbon is highly transparent and exhibits a granular nano-texture, whose grain size is tunable by selecting adequate pressure and temperature conditions.

DOI： 10.1080/08957959.2019.1700981

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掲載種別：研究論文（学術雑誌）  

© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. In this work, we use extended X-ray absorption fine structure (EXAFS) data collected using nano-polycrystalline diamond anvil cell to study the atomic arrangement in Zr–Cu metallic glass in high pressure (HP) conditions. To reveal the microscopic details of stress accommodation mechanism, we performed molecular dynamics (MD) simulations of the HP atomic arrangement. By comparing the experimental and the calculated Zr and Cu K-edge EXAFS signal we prove the realistic character of the computer simulations. A detailed geometrical analysis of the simulated atomic configurations shows that with increasing hydrostatic pressure the local structure of Zr–Cu amorphous alloy becomes gradually dominated by Cu-centred icosahedral structural motifs involving fivefold symmetry incompatible with crystalline ordering. The variation of the short-range order is attributed to preferential straining of mechanically soft bonds between zirconium atoms.

DOI： 10.1080/08957959.2019.1695797

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

© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. The use of nanopolycrystalline diamond has allowed a systematic study on deformation of polycrystalline diamond composites (PCDCs). Bulk PCDCs samples containing either Co or SiC as a binding agent were deformed under high pressure and temperature to strains up to 18% at strain rates ∼10−5 s−1. All samples exhibit strong work hardening. The strength of PCDCs depends on the amount and type of binding agents and is consistently weaker than that of diamond single crystals. The weakening may be due to the binder materials, which play an important role in affecting grain boundary structures. In SiC-based PCDC, significant grain fragmentation occurs. Nearly all grain boundaries are wetted by SiC after large deformation, resulting in lower strength. In Co-based PCDC, the microstructure is dominated by dislocations, deformation twins, and separated grain boundaries. The density of deformation twins increases significantly with strain, with the twin domain width reaching as low as 10–20 nm at 14% strain.

DOI： 10.1080/08957959.2019.1695254

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

© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. Deep-ultraviolet continuous-wave photoluminescence spectroscopy is performed for nano-polycrystalline diamond (NPD) synthesized by a high pressure high-temperature technique. NPD exhibits clear deep-ultraviolet emissions, which originate from intrinsic excitonic transitions assisted by a momentum-conserving phonon with a photon. Surprisingly, the peak emission energy is about 30 meV higher than that of the single-crystalline diamond. Raman scattering spectroscopy indicates that the energy difference should originate from the excitonic properties of the NPD and not the phonon. Hence, NPD has a large bandgap compared to single-crystalline diamond.

DOI： 10.1080/08957959.2019.1702658

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN INST METALS & MATERIALS  

We disperse InP nanocrystals into nano-polycrystalline diamond during the direct conversion from graphite as a possible technique to control its solid-state properties. We synthesize diamond, using the high-pressure, high-temperature technique, which encapsulates an InP alloy in close contact with the graphite starting material. X-ray diffraction of the synthesized sample suggests the formation of polycrystalline diamond where the mixed crystals contain InP. Cross-sectional transmission electron microscopy shows the existence of InP nanocrystals with sizes up to approximately 100 nm. The existence of the InP elements can promote the formation of larger crystalline diamond grains arising from liquid sintering, which show a larger grain size over 400nm compared with the regions without InP, where a grain size of approximately 50 nm is observed.

DOI： 10.2320/matertrans.MT-M2020124

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© 2019 Elsevier B.V. We report the large reversible magnetocaloric effect (MCE) in the cubic pyrochlores R2Mn2O7 (R = Dy, Ho, Yb) near their second-order ferromagnetic (FM) transition at TC ≈ 39 K due to a simultaneous FM ordering of rear-earth R3+ and transition-metal Mn4+ localized moments. Under the magnetic field change of 1 T (7 T), the maximum magnetic entropy change −ΔSMmax is 5.7 (20.1), 4.3 (18.4), 3.9 (13.9) J·kg−1·K−1, and the estimated magnetic refrigerant capacity RC reaches 20.0 (564), 18.4 (503.7), 13.1 (371.4) J·kg−1 for Dy2Mn2O7, Ho2Mn2O7, and Yb2Mn2O7, respectively. We have discussed their magnetic properties and its correlation with MCE in terms of the intrinsic single-ion anisotropy of R3+ ions. Our results demonstrate that R2Mn2O7 cubic pyrochlores constitute a promising material platform for magnetic refrigeration applications in the intermediate temperature range.

DOI： 10.1016/j.jmmm.2019.165494

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER  

© 2018 Académie des sciences Nano-polycrystalline diamond cubes with an edge length of 6 mm have been used as anvils for Kawai-type multianvil apparatus. The maximum pressure of ∼88 GPa was confirmed based on in situ X-ray diffraction measurements using nano-polycrystalline diamond anvils with a truncation of 1.0 mm, which is more than 50% higher than the pressure (∼56 GPa)achieved at the same press load using sintered-diamond anvils. The X-ray transparency of the nano-polycrystalline diamond anvil was found to be about 10–100 times as high as that of sintered-diamond anvils for a wide range of photon energies (∼30–130 keV), leading to high-quality X-ray imaging and diffraction profiles of the sample under pressure, even through the anvils. It is expected that further optimization of the pressure medium and gasket would lead to pressures far higher than 100 GPa without sacrificing the advantages of the multianvil apparatus over diamond anvil cells.

DOI： 10.1016/j.crte.2018.07.005

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2018 The Japan Society of Applied Physics. We propose a simple and easy electrode formation technique on nanopolycrystalline diamond (NPD) synthesized by a high-temperature and high-pressure technique. The stronger light absorption nature of NPD than of standard transparent diamond enables the laser irradiation process on NPD. Pulsed laser irradiation using an ArF excimer laser under atmospheric condition drastically reduced the resistance of the NPD surface by forming graphite. Repetition of the laser irradiation reduced the resistance, showing a resistance of 300 Ω for the laser-irradiated area of 100 × 150 μm 2 . These results indicate the applicability of pulsed laser irradiation to an NPD apparatus having a conductive electrode, as well as electronic device processes.

DOI： 10.7567/JJAP.57.118004

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

When high pressure is applied to Ce-Al metallic glasses, their disordered atomic structure exhibits some unusual properties like polyamorphism or transformation into a crystalline phase. In this work, we probe the atomic arrangement of Ce55Al45 and Ce75Al25 glasses by X-ray absorption spectroscopy and X-ray diffraction in the pressure range of 0–30 GPa. The pressure-dependent parameters of local environment of cerium atoms are evaluated by extended X-ray absorption fine structure (EXAFS) fitting. We demonstrate that due to compositional dependence of stiffness of Ce-Al pairs, densification of Ce55Al45 is accompanied by an increase of atomic size mismatch between Ce and Al stabilizing the amorphous phase, while a decrease of the mismatch is observed in Ce75Al25 alloy which eventually leads to its devitrification at 25 GPa.

DOI： 10.1016/j.jallcom.2018.05.077

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

Using a turbostratic pyrolytic boron nitride as a starting material, we synthesized a variety of ultrahard polycrystalline cubic boron nitride (PcBN) as a function of the heating duration changing from 1 to 60 min under a constant temperature and pressure conditions (1950 degrees C and 25 GPa) using a multi-anvil apparatus. When the heating duration was less than 13 min, ultrafine nano-polycrystalline cBN (U-NPcBN) with the mean grain size of < 50 nm was produced. Among these U-NPcBNs those synthesized with 11-13 min were found to have a uniform texture composed purely of cBN (i.e. with no wurzite BN residue) and a Knoop hardness of > 53 GPa, which is 20% higher than that of the hardest conventional binderless PcBN in practical use. Furthermore, the PcBNs synthesized with 18-20 min showed a unique nanocrystalline texture composed of relatively coarse grains dispersed in a fine grained matrix and even higher Knoop hardness (54.5-55.2 GPa).

DOI： 10.1016/j.jeurceramsoc.2018.02.023

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2018 IOP Publishing Ltd. Extended x-ray absorption fine structure (EXAFS) at the Cd K edge and diffraction patterns have been measured on CdTe as a function of pressure from 100 kPa (1 bar) to 5 GPa using a cell with nano-polycrystalline diamond anvils and an x-ray focussing scanning spectrometer. Three phases-zincblende (ZB), mixed cinnabar-ZB and rocksalt (RS)-are well distinguished in different pressure intervals. The bond compressibility measured by EXAFS in the ZB phase is slightly smaller than the one measured by diffraction and decreases significantly faster when the pressure increases; the difference is attributed to the effect of relative vibrations perpendicular to the Cd-Te bond. The parallel mean square relative displacement (MSRD) decreases, the perpendicular MSRD increases when the pressure increases, leading to an increasing anisotropy of relative atomic vibrations. A constant-Temperature bond Grüneisen parameter (GP) has been evaluated for the ZB phase and compared with the constant-pressure bond GP measured in a previous experiment; an attempt is made to connect the bond GPs measured by EXAFS and the more familiar thermodynamic GP and mode GPs; the comparisons suggest the inadequacy of the quasi-harmonic approximation to deal with the local vibrational properties sampled by EXAFS.

DOI： 10.1088/1361-648X/aac188

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

We investigated inherent electronic properties of ultra-hard nano-polycrystalline diamond (NPD) synthesised at 15 GPa and 2300 degrees C. NPD exhibited a p-type semiconducting property with a resistivity of 1 x 10(6) and 4 x 10(2) Omega cm at 400 degrees C and 800 degrees C, respectively, with activation energies as high as 1.2 eV. The mobility was 2 cm(2)/Vs at 800 degrees C. The observed transport was considered to be attributed to grain boundary. Cathodoluminescence spectra show defect-related peaks with dominant peaks at 2.8 eV close to band-A and peaks below 2 eV, which is possibly related to crystal defects. In contrast, photoluminescence excited with a wavelength of 405 nm resonantly excited peaks having energies lower than 2.1 eV. The large density of crystalline defects such as grain boundaries and impurities in the NPD would result in the characteristic electronic and optical properties.

DOI： 10.1016/j.diamond.2018.03.007

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

The super hard material of "compressed graphite" (CG) has been reported to be formed under compression of graphite at room temperature. However, it returns to graphite under decompression. Neutron-irradiated graphite, on the other hand, is a unique material for the synthesis of a new carbon phase, as reported by the formation of an amorphous diamond by shock compression. Here, we investigate the change of structure of highly oriented pyrolytic graphite (HOPG) irradiated with neutrons to a fluence of 1.4 x 10(24) n/m(2) under static pressure. The neutron-irradiated HOPG sample was compressed to 15 GPa at room temperature and then the temperature was increased up to 1500 degrees C. X-ray diffraction, high-resolution transmission electron microscopy on the recovered sample clearly showed the formation of a significant amount of quenchable-CG with ordinary graphite. Formation of hexagonal and cubic diamonds was also confirmed. The effect of irradiation-induced defects on the synthesis of quenchable-CG under high pressure and high temperature treatment was discussed. Published by AIP Publishing.

DOI： 10.1063/1.5011209

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

Detailed pressure-temperature phase diagrams of heavy lanthanide sesquisulfides Ln(2)S(3) (Ln = Yb and Lu) have been investigated by in-situ x-ray diffraction experiments under high pressure and high temperature using synchrotron radiation and multi-anvil press. Based on the results of the in-situ observation, the single gamma-phase (Th3P4-type structure, I (4) over bar 3d) samples of Ln(2)S(3) (Ln = Yb and Lu) have been synthesized under high pressure. The physical properties of the compounds were studied by electrical resistivity, specific heat, and magnetic susceptibility measurements between 2 K and 300 K. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2017.11.090

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

Highly oriented pyrolytic graphite (HOPG) is a unique source material for the synthesis of new types of diamond. It can transform to layered nano-polycrystalline diamond (NPD) under static high pressure and high temperature (HPHT) and to "amorphous diamond" by introducing structural defects by neutron irradiation followed by shock compression. Here, we investigated the structural change of the neutron-irradiated HOPG through a HPHT treatment at 2300 degrees C and 15 GPa by Raman, X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray absorption near edge structure (XANES) analyses. The recovered sample consists of randomly oriented nanodiamonds (50-100 nm), showing clearly a different microtexture from those of the layered NPD and "amorphous diamond" reported by the previous studies. This is likely as a result of competing effects of the introduction of irradiation-induced defects, which provided the preferential nucleation sites for cubic diamond, and their partial recovery upon annealing during the HPHT treatment. The present result suggests that NPDs with various crystalline structures can potentially be synthesized from neutron-irradiated HOPG by controlling the density and distribution of the defects introduced.

DOI： 10.1016/j.diamond.2018.01.001

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掲載種別：研究論文（学術雑誌）  

© 2018 Author(s). By combining theoretical predictions and in-situ X-ray diffraction under high pressure, we found a novel stable crystal structure of Li3PS4 under high pressures. At ambient pressure, Li3PS4 shows successive structural transitions from γ-type to β-type and from β-type to α type with increasing temperature, as is well established. In this study, an evolutionary algorithm successfully predicted the γ-type crystal structure at ambient pressure and further predicted a possible stable δ-type crystal structures under high pressure. The stability of the obtained structures is examined in terms of both static and dynamic stability by first-principles calculations. In situ X-ray diffraction using a synchrotron radiation revealed that the high-pressure phase is the predicted δ-Li3PS4 phase.

DOI： 10.1063/1.5011401

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

In the bulk silicate Earth, chlorine is more depleted than other elements with similar volatilities; however, the cause of terrestrial chlorine depletion is not well understood. Two major hypotheses have been proposed to explain this depletion: Incorporation into the Earth's metallic core and escape to space. The former hypothesis can be tested by investigating the partitioning of chlorine between iron-rich metallic liquids and silicate melts. In this study, we investigated the experimental partitioning of chlorine between iron-rich metallic liquids and silicate melts at pressures from 4 to 23 GPa and temperatures from 1,650 to 2,400 degrees C using multi-anvil presses. The results demonstrate that chlorine is moderately to highly lithophile under the experimental conditions. In sulfur-free experiments, chlorine becomes slightly more siderophile as temperature increases and less siderophile as pressure increases. For sulfur-bearing experiments, no significant effects of pressure or temperature were observed. Based on these data and thermodynamic considerations, we obtained empirical laws to estimate chlorine partition coefficients between iron-rich metallic liquids and silicate melts. Under the P-T conditions that would have controlled metal-silicate equilibration during core segregation in the Earth, the calculated metal-silicate partition coefficients for chlorine are much lower than unity. This result suggests that terrestrial chlorine that may have been present in the accreting Earth was not partitioned into its core, supporting that escape to space is the more likely hypothesis. If terrestrial chlorine was lost to space, chlorine depletion may have resulted from the loss of the primordial hydrosphere during the formation of the Earth.

DOI： 10.1002/2017GC007159

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

Using a turbostratic pyrolytic boron nitride produced by a chemical vapor deposition process as a starting material, we conducted experiments for synthesizing polycrystalline cubic boron nitride (PcBN) at a temperature of 1600-2600 degrees C and pressure of 25 GPa with a multi-anvil high-pressure apparatus. Moreover, we evaluated the microstructure and hardness characteristics of the synthesized PcBN. The results showed that a complete single-phase PcBN without residual wurtzite BN was produced at 1900 degrees C or higher and a nano-polycrystalline cBN (NPcBN) having a mean grain size smaller than 100 nm could be synthesized at a temperature of 1950 degrees C or lower under a pressure of 25 GPa. Furthermore, we found that a single-phase NPcBN (CGD-NPcBN) having a characteristic microstructure of dispersed relatively coarse grains in a fine polycrystalline structure, which was harder than 53.5 GPa in Knoop hardness, was produced at a temperature range of 1900-1950 degrees C. In particular, at 1950 degrees C, CGD-NPcBN having a Knoop hardness of 54.7 GPa, which is 25% higher than that of the hardest binderless PcBN tool currently in practical use, can be synthesized. In addition, we verified that the Knoop hardness of the single-phase PcBN with a uniform microstructure increased with decreasing mean grain size, which complied with the Hall fetch relationship.

DOI： 10.1016/j.diamond.2017.04.020

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

Cerium phosphide undergoes a unit-cell volume discontinuity without any structural phase transitions upon application of a high pressure of similar to 10 GPa. This phenomenon is attributed to a change in the electronic charge distribution of the cerium in CeP, but to date no direct experimental verification for this hypothesis has been presented. Here, we report a Ce L-3-edge X-ray absorption spectroscopy study under pressure, which provides direct compelling evidence of an electronic transition associated with the above-mentioned isostructural volume discontinuity. The present results should be relevant to the understanding of the phenomenon of pressure induced isostructural transitions involving unit-cell volume collapse.

DOI： 10.1039/c7cp03022c

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

A large-strain, torsional deformation apparatus has been developed based on diamond anvil cells at high pressures, up to 135 GPa with a help of hard nano-polycrystalline diamond anvils. These pressure conditions correspond to the base of the Earth's mantle. An X-ray laminography technique is introduced for high-pressure in situ 3D observations of the strain markers. The technique developed in this study introduces the possibility of the in situ rheological measurements of the deep Earth materials under ultrahigh-pressure conditions. Published by AIP Publishing.

DOI： 10.1063/1.4979562

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

We present a systematic experimental study on the phase transition, lattice microstrain, and order-disorder of cations for garnets in the majorite-pyrope system. Polycrystalline gem-quality garnets were synthesized at high pressure and high temperature using a Kawai-type multi-anvil apparatus. A phase transition from a cubic to tetragonal structure is clearly observed for garnets with the majorite content of more than 74 mol % through X-ray diffraction (XRD) and Raman scattering studies. Microstrain of garnets, evaluated with the Williamson-Hall plot on XRD profiles, shows a nonlinear dependence of the garnet compositions. The variation of the XRD peak broadening suggests the lattice microstrain of these garnets may be associated with the local structural heterogeneities due to the substitution of different cations via the coupled substitution (Mg2+ + Si4+ = 2Al(3+)) in the garnet structure. The width variation of Raman scattering peaks indicates that cation disorder occurs in the garnet structure for intermediate compositions. It is found that intermediate garnets and end-members have a minimum of microstrain, while those between end-members and intermediate compositions possess a larger microstrain.

DOI： 10.1007/s00269-016-0852-3

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

Lingunite (hollandite with Na contents of 80-85 mol%) discovered in the shock veins of strongly shocked meteorites is an important signature of shock metamorphism. To seek the stability region of lingunite, phase relations in the system KAlSi3O8-NaAlSi3O8 have been investigated by multi-anvil experiments at pressures of 20-23 GPa and temperatures of 1873 and 2273 K. Phase assemblages of hollandite + jadeite + stishovite, hollandite + calcium ferrite-type NaAlSiO4 + stishovite and hollandite single phase have been recovered, depending on the pressure-temperature conditions and the compositions of starting materials. Both pressure and temperature have large effects on the solubility of Na in hollandite, and hollandite with 79 mol% Na, similar to the natural lingunite in terms of Na content, has been firstly synthesized at 22 GPa and 2273 K. The stability region of K0.2Na0.8AlSi3O8 hollandite is comparable to the typical pressure-temperature conditions of the shock veins of strongly shocked meteorites (20-25 GPa and 2273-2500 K).

DOI： 10.1007/s00269-016-0834-5

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

Transparent ceramics are important for scientific and industrial applications because of the superior optical and mechanical properties. It has been suggested that optical transparency and mechanical strength are substantially enhanced if transparent ceramics with nanocrystals are available. However, synthesis of the highly transparent nano-crystalline ceramics has been difficult using conventional sintering techniques at relatively low pressures. Here we show direct conversion from bulk glass starting material in mutianvil high-pressure apparatus leads to pore-free nano-polycrystalline silicate garnet at pressures above similar to 10 GPa in a limited temperature range around 1,400 degrees C. The synthesized nano-polycrystalline garnet is optically as transparent as the single crystal for almost the entire visible light range and harder than the single crystal by similar to 30%. The ultrahigh-pressure conversion technique should provide novel functional ceramics having various crystal structures, including those of high-pressure phases, as well as ideal specimens for some mineral physics applications.

DOI： 10.1038/ncomms13753

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

A novel long-period superlattice Mg77Zn9Yb14 phase, whose dimensions are described as root 3 x root 3 x 3 with respect to the original hexagonal close-packed Mg lattice, has been found in Mg97Zn1Yb2 alloys synthesized under high pressure (5 GPa) and at high temperature (723 K). A preliminary model structure is constructed based on atomic-resolution electron microscopy and first-principles calculations, providing local configurations around Yb atoms whose sizes appear to be smaller than those of a divalent Yb. This may be reasonably attributed to an applied high-pressure effect (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.scriptamat.2016.04.022

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

Phase relations in the system MgSiO3-Al2O3 have been determined for pressures from 15 to 52 GPa and at a temperature of 2000 K from in situ synchrotron X-ray diffraction measurements obtained using sintered diamond anvils in a multi-anvil apparatus. A wide two-phase region of garnet and corundum is found to exist up to 27 GPa; at higher pressures, a phase assemblage of aluminous bridgmanite and corundum is stabilized. The solubility of Al2O3 in bridgmanite and that of MgSiO3 in corundum are highly dependent on pressure; the Al2O3 content in bridgmanite increases from 12 mol% at 27 GPa to 29 mol% at 52 GPa, forming bridgmanite with the pyrope composition (25 mol% Al2O3) at about 45 GPa. In contrast, the MgSiO3 content in corundum decreases from 24 mol% at 27 GPa to 9 mol% at 52 GPa. The minimum pressure where the pyropic bridgmanite is formed is significantly higher than the result of the earlier study (similar to 37 GPa) on the pyrope composition. These results suggest the Al2O3 content in bridgmanite and the MgSiO3 content in corundum are good pressure indicators in the mixed-phase region at pressures above 30 GPa, where virtually no pressure references are available for quench experiments. The new phase diagram in the system MgSiO3-Al2O3 confirms that bridgmanite is the dominant host mineral for Al2O3 in the pyrolitic or peridotitic compositions under the pressure and temperature conditions of the Earth's lower mantle. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2016.05.006

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

To explore the microscopic response of a metallic glass (MG) to an applied hydrostatic load we performed a high-pressure extended x-ray absorption fine structure (EXAFS) study of the Zr66.7Cu33.3 amorphous alloy. EXAFS fitting revealed that on compression, Zr-Zr pairs are strained preferentially. Strong Zr-Cu interactions contribute to the stiffness of dominant Cu-centered clusters and the overall compressibility of the MG is mostly determined by the softer bonds between the Zr atoms belonging to the clusters' outer shell. Stress accommodation is accompanied by a variation of bonding preferences, which is consistent with the observed hierarchy of elastic constants of different atomic pairs.

DOI： 10.1103/PhysRevB.93.144115

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

The strength of polycrystalline diamond (PCD) was investigated through a high pressure (P) and temperature (T) deformation experiment. Prior to the deformation experiment, two bulk samples were sintered back to back under identical conditions with two different precursors, which shared identical initial grain size distribution. Precursor of one sample (2E) had lower concentration of crystalline defects than that of the other sample (15). In crushing strength tests, precursor of 2E exhibited an enhanced crushing strength compared to that of 1S. During the high P-T deformation experiment, the two samples were stacked back to back and deformed together. Their mechanical properties were investigated in situ using synchrotron X-ray diffraction and imaging in the deformation DIA apparatus. The strain data based on imaging showed that the two samples were deformed at identical strain rates (ca. 1.5 x 10(-5) s(-1)) and analysis based on lattice plane distortions in the diffraction patterns showed that sample 2E exhibits marginally higher strength than that of sample 1S. The X-ray data indicate that, upon deformation, larger elastic lattice strain builds up within the grains in sample 2E, indicating greater strength at grain-to-grain level in this sample. In addition, lower micro-stress levels are evidenced upon hydrostatic loading of sample 2E, strongly indicating a better sintering state than that in sample 1S. We interpret these differences as due to a lower defect concentration, particularly on the grain surfaces of the precursor powder, that results in stronger diamond-diamond bonding. Altogether, these data suggest that the use of diamond grains with reduced defect concentration and cleaner surfaces as precursors will likely improve the wear resistance of the resulting PCD via stronger individual grains and better sintering. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.diamond.2015.09.001

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

We have investigated the local and electronic structure of solid rubidium by means of x-ray absorption spectroscopy up to 101.0 GPa, thus doubling the maximum investigated experimental pressure. This study confirms the predicted stability of phase VI and was completed by the combination of two pivotal instrumental solutions. On one side, we made use of nanocrystalline diamond anvils, which, contrary to the more commonly used single crystal diamond anvils, do not generate sharp Bragg peaks (glitches) at specific energies that spoil the weak fine structure oscillations in the x-ray absorption cross section. Second, we exploited the performance of a state-of-the-art x-ray focussing device yielding a beam spot size of 5 x 5 mu m(2), spatially stable over the entire energy scan. An advanced data analysis protocol was implemented to extract the pressure dependence of the structural parameters in phase VI of solid Rb from 51.2 GPa up to the highest pressure. A continuous reduction of the nearest neighbour distances was observed, reaching about 6% over the probed pressure range. We also discuss a phenomenological model based on the Einstein approximation to describe the pressure behaviour of the mean-square relative displacement. Within this simplified scheme, we estimate the Gruneisen parameter for this high pressure Rb phase to be in the 1.3-1.5 interval. (C) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4921894

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

The elastic wave velocities of polycrystalline Mj(80)Py(20) garnet along the majorite-pyrope system have been measured at pressures up to 21 GPa and temperatures up to 2,000 K using ultrasonic interferometry in conjunction with in situ X-ray diffraction techniques in a Kawai-type multi-anvil apparatus. The elastic moduli of Mj(80)Py(20) garnet and their pressure and temperature derivatives are determined by a two-dimensional linear fitting of the present experimental data, yielding: K (S) = 161.5 (7) GPa, a,K (S)/a,P = 4.42 (4), a,K (S)/a,T = -0.0154 (2) GPa/K, G = 86.2 (2) GPa, a,G/a,P = 1.28 (1), a,G/a,T = -0.0096 (5) GPa/K. The present results together with those of the studies on the majorite-pyrope solid solutions suggest the pressure and temperature derivatives of elastic moduli are insensitive to the majorite content in the majorite-pyrope system. The velocity gradients of the majoritic garnets in the majorite-pyrope system are 3 6 times lower than those required to account for the high seismic velocity gradients observed in the mantle transition zone.

DOI： 10.1007/s00269-014-0712-y

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掲載種別：研究論文（国際会議プロシーディングス）  

The strength of Polycrystalline Diamond (PCD) was investigated through a high Pressure (P) and Temperature (T) deformation experiment. Two samples were sintered back to back under identical conditions and shared identical initial grain size distribution. One sample (4.4a) had lower concentration of crystalline defects than the other (3.4a). In crushing strength tests conducted prior to the deformation experiment, 4.4a exhibited an enhanced crushing strength compared to 3.4a. During the high P-T deformation experiment, the samples were stacked and deformed together and their mechanical properties were investigated in situ using synchrotron Xray diffraction and imaging. The strain data based on imaging showed that the two samples were deformed at the same rate (ca. 1.5 × 10-5 s-1). Analysis of the diamond lattice plane distortions in the diffraction patterns showed that sample 4.4a exhibits slightly greater strength, especially towards large amounts of strain. We interpret this difference as due to a better sintering for 4.4a, thanks to lower defect concentration and cleaner grain surfaces of the precursor powder, which results into stronger diamond-diamond bonding. These data suggest that the use of diamond grains with reduced defect concentration and cleaner surfaces as a precursor improves the bulk strength and the wear resistance of the resulting PCD.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN INST METALS & MATERIALS  

The crystal structures of Mg85Zn6Y9 alloy under 3 GPa were investigated between room temperature and 973K using in situ X-ray diffraction (XRD). In addition, the crystal structures and microstructures of Mg85Zn6Y9 alloys that were recovered after being heated at various temperatures under 3 GPa were also investigated. The in situ XRD analysis results indicated that 10H- and 18R-type long-period stacking orders (LPSOs) were stable below 673K under 3 GPa; however, the D0(3) and alpha-Mg structures, which were not observed at ambient pressure, emerged at 873K in the sample under 3 GPa. When the temperature was increased to 973 K, the D0(3) and alpha-Mg phases fused. The D0(3) and alpha-Mg phases were also confirmed to be present in Mg85Zn6Y9 alloy that was recovered after being heated at 873K under 3 GPa. In contrast, the XRD pattern of the Mg85Zn6Y9 alloy that was recovered after being heated at 973K under 3 GPa indicated the presence of the 18R-type LPSO, D0(3), and alpha-Mg structures. These results indicate that three phases-18R-type LPSO, D0(3), and alpha-Mg-were formed during cooling from the molten state at 3 GPa. These results further suggest that the D0(3), alpha-Mg, and 18R-type LPSO are energetically very similar under 3 GPa.

DOI： 10.2320/matertrans.MH201413

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

The pressure dependence of the superconducting transition temperature T-c, the local structure, and the electronic properties of the iron chalcogenide superconductor FeSe0.5Te0.5 was investigated by means of SQUID magnetometry and site-selective polarized x-ray absorption spectroscopy at the iron and selenium K-edges. The measurements reveal a discontinuous decrease of the local bond distances by crossing a tetragonal to monoclinic structural phase transition at p(S) similar to 2.7 GPa. The electronic structure, however, evolves evenly, but the superconducting properties are highly affected by changes in the local structure. These results underline the close connection of the lattice and the superconductivity in the iron-based superconductors.

DOI： 10.1103/PhysRevB.90.174505

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

A Kawai-type multianvil apparatus operated in a 60 MN press has been constructed for materials synthesis at high pressure and temperature. After having tested various tungsten carbide anvils and optimization of the cell assembly for this novel apparatus, we are now able to perform synthesis experiments of high-pressure phases at temperatures to similar to 2500 degrees C with relatively large sample volumes of about 2 cm(3) in a pressure range up to about 16 GPa. Using this apparatus, synthesis of high-quality rods of sintered nano-polycrystalline diamond with dimensions to 1 cm in both diameter and length has been routinely made, which should be important as new anvil material for high-pressure mineral physics studies, as well as for some industrial applications. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2013.09.007

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

Spin transition and substitution of Fe3+ in Fe3+AlO3-bearing MgSiO3 perovskite (Pv) and post-perovskite (PPv) were examined up to 200 and 165 GPa, respectively, at room temperature by X-ray emission spectroscopy (XES) and XRD. The results of XES and XRD indicate that in Pv high spin (HS) Fe3+ at the dodecahedral (A) site replaces Al at the octahedral (B) site and becomes low spin (LS) between 50 and 70 GPa with pressure, while in PPv LS Fe3+ occupies the B-site and Al occupies the A-site above 80-100 GPa. The Fe3+ Al coupled substitution seems to be at work in both Pv and PPv. Combining these results on Fe3+ with the recent first-principles calculations on Fe2+ in Pv and PPv, the spin transition and substitution of iron in pyrolitic lower mantle minerals are proposed. Further, their effects on iron-partitioning among the lower mantle minerals are discussed. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2013.12.008

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

The local structure and electronic properties of Rb1-xFe 2-ySe2 are investigated by means of site selective polarized x-ray absorption spectroscopy at the iron and selenium K edges as a function of pressure. A combination of dispersive geometry and a nanodiamond anvil pressure cell has permitted us to reveal a steplike decrease in the Fe-Se bond distance at p≃11 GPa and, at the same pressure, the local atomic structure of Rb1-xFe2-ySe2 becomes more ordered. Thus, at this pressure the phase separation might be suppressed, which has a large influence on the electronic structure, as evidenced by changes in the Fe K-edge prepeak. The present results provide compelling evidence that the reemerging superconductivity in A1-xFe2-ySe2 is closely related to the transition to a locally more ordered state, which has a different electronic structure. © 2013 American Physical Society.

DOI： 10.1103/PhysRevB.88.180506

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

Wear resistance of nano-polycrystalline diamond (NPD) rods containing various amounts of hexagonal diamond has been tested with a new method for practical evaluation of the wear-resistance rate of superhard ceramics, in addition to the measurements of their Knoop hardness. The wear resistance of NPD has been found to increase with increasing synthesis temperature and accordingly decreasing proportion of hexagonal diamond. A slight increase in Knoop hardness with the synthesis temperature also has been observed for these samples, consistent with the results of the wear-resistance measurements. These results suggest that the presence of hexagonal diamond would not yield any observable increase in both hardness and wear resistance of NPD, contradictory to a recent prediction suggesting that hexagonal diamond is harder than cubic diamond. It is also demonstrated that NPD is superior to single crystal diamond in terms of relatively homogeneous wearing without any significant chipping/cracking.

DOI： 10.3103/S1063457612060081

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

The Vickers hardness of polycrystalline gamma-boron (gamma-B) was measured using a diamond indentation method. The elastic properties of polycrystalline gamma-B were determined using an ultrasonic measurement method. Under a loading force of up to 20 N our test gave an average Vickers hardness in the asymptotic hardness region around 30.3 GPa. We also measured the hardness and elastic properties of polycrystalline beta-B and cubic boron nitride Ti3SiC2 (PcBN) for comparison. The hardness and elastic properties of polycrystalline gamma-B were found to be very close to those of PcBN. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.scriptamat.2012.04.032

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

Disorder-activated phonon behaviors of the cubic rocksalt-type semiconductor alloy Li(1-x)/2Ga(1-x)/2MxO (M=Mg, Zn) prepared by high-pressure and high-temperature method has been studied by Raman scattering analysis. The LO Raman phonon in Li(1-x)/2Ga(1-x)/2MxO was found to exhibit a distinct two-mode behavior. The compositional dependence of Raman frequency, peak-width, and intensity has been discussed. A model associated with a composite mode of the Brillouin zone center and edge phonons combined with phonon dispersion curves determined by first-principle calculations were employed to explain the asymmetric broadening of the LO phonon mode. The broadening and asymmetric Raman line-shape in Li(1-x)/2Ga(1-x)/2MxO can be interpreted as a composite mode of the softening Brillouin zone center mode and the Brillouin zone edge mode. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4739766]

DOI： 10.1063/1.4739766

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

Thermoelastic properties of synthetic Mg3Al2Si3O12 pyrope garnet have been measured at high pressure and high temperature by using in situ energy-dispersive X-ray diffraction, using a Kawai-type multi-anvil apparatus. Measurements have been conducted up to 19 GPa and 1,700 K, equivalent to the P-T conditions of the middle part of mantle transition zone. Analyses of the room-temperature P-V data to a third-order Birch-Murnaghan (BM) equation of state (EoS) yields: V (0) = 1,500 +/- A 1 (3), K (0) = 167 +/- A 6 GPa and = 4.6 +/- A 0.3. When fitting the entire P-V-T data using a high-temperature Birch-Murnaghan (HTBM) EoS at a fixed = 4.6, we obtain V (0) = 1,500 +/- A 2 (3), K (T0) = 167 +/- A 3 GPa, (a,K/a,T) (P) = -0.021 +/- A 0.009 GPa K-1 and alpha (300) = (2.89 +/- A 0.33) x 10(-5) K-1. Fitting the present data to the Mie-Gruneisen-Debye (MGD) EoS with Debye temperature I similar to(0) = 806 K gives gamma(0) = 1.19 and 1.15 at fixed q = 1.0 and 1.5, respectively. Comparison of these fittings with two different approaches, we propose to constrain the bulk modulus and its pressure derivative to K (0) = 167 GPa and = 4.4-4.6, as well as the Gruneisen parameter to gamma (0) = 1.15-1.19.

DOI： 10.1007/s00269-012-0514-z

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

Elastic wave velocities of synthetic polycrystalline Mg3Al2(SiO4)(3) garnet have been successfully measured to 20 GPa and temperatures up to 1700 K by ultrasonic interferometry combined with energy-dispersive synchrotron x-ray diffraction in a Kawai-type multi-anvil apparatus. Compressional (Vp) and shear (Vs) wave velocities as well as the adiabatic bulk (Ks) and shear (G) moduli exhibit monotonic increase with increasing pressure and decrease with increasing temperature, respectively. Two-dimensional (P-T) linear fittings of the present data yield the following parameters: K-S0 = 170.0(2) GPa, partial derivative Ks/partial derivative P = 4.51(2), partial derivative Ks/partial derivative T = -0.0170(1) GPa/K, G(0) = 93.2(1) GPa, partial derivative G/partial derivative P = 1.51(2), and partial derivative G/partial derivative T = -0.0107(1) GPa/K, which is in good agreement with the earlier results by Brillouin scattering and/or ultrasonic measurements at relatively low P-T conditions. The observed linear pressure and temperature dependence in both Vp and Vs is in contrast to the non-linear behavior of Vp and Vs for majorite garnet with the pyrolite composition, in particular for Vs. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4736407]

DOI： 10.1063/1.4736407

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

A two-step procedure of two-dimensional polymer constructed from benzo[b]trithiophene (BTT) was proposed by electrochemical polymerization and thermal conversion. Electropolymerized BTT oligomer on an electrode was thermally converted to conjugated polymer. Obtained conductive material is found to retain BTT structure by Raman spectra and to extend pi conjugation by absorption spectra.

DOI： 10.1246/cl.2012.140

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

There are still large discrepancies among the previous reports on the spin transition of iron in Mg-perovskite (Pv). To alleviate this problem, we examined the spin state of Fe3+ in Mg0.85Fe0.153+Al0.15Si0.85O3 Pv up to 200 GPa by X-ray emission spectroscopy (XES) and X-ray diffraction (XRD). The gradual decrease of the high spin (HS) ratio of Fe3+ by low temperature annealing of the samples above similar to 60 GPa in XES and the change of the trend of unit cell volumes with pressure by annealing at 50-60 GPa in XRD indicate that Fe3+ occupies the A-site and is HS below similar to 50 GPa but above 50-60 GPa it gradually replaces Al at the B-site through cation exchange reaction by annealing and becomes low spin (LS), while Fe3+ remaining at the A-site is HS up to 200 GPa. This means that the spin state of Fe3+ depends on Fe3+ occupancies between the A- and B-sites and these Fe3+ occupancies are strongly controlled by the synthesis condition and annealing temperature of the samples through the cation exchange reaction. The present results combined with the previous reports indicate that in Al-bearing Mg-Pv in the lower mantle Fe2+ occupies the A-site and remains HS for the whole lower mantle, while Fe3+ occupies the A-site and is HS below similar to 50 GPa but above 50-60 GPa it replaces Al at the B-site and becomes LS, on the assumption that spin transition pressure of Fe2+ at the A-site is higher than that of Fe3+ at the same site. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2011.12.006

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

The phase relations in boron have been investigated at high pressure and high temperature using a multianvil apparatus, and the quenched sample has been analyzed by x-ray diffraction, Raman spectra, and transmission electron microscopy. We demonstrate that gamma-B-28 can be synthesized over a wide pressure and temperature range, and alpha-tetragonal B-50 (T-B-50) is obtained at higher temperatures and similar pressures. The phase boundary of the beta-B-106, gamma-B-28, and T-B-50 is determined at pressures between 7.0 and 18GPa and the temperatures of 500-2200 degrees C. The results suggest that T-B-50 might be an intermediate phase formed for kinetic reasons (Ostwald rule) on the way from beta-B-106 to beta-tetragonal B-192 (T-192) and gamma-B-28 to T-192.

DOI： 10.1103/PhysRevB.85.014107

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

The stability and decomposition of graphitic C3N4 (g-C3N4) were studied in the pressure and temperature range of 10-25 GPa and up to 2000 degrees C by multi-anvil experiments and phase characterization of the quenched products. g-C3N4 was found to remain stable at relatively mild temperatures, but decomposes to graphite and nitrogen at temperatures above 600-700 degrees C and up to 15 GPa, while it decomposes directly to diamond (plus nitrogen) above 800-900 degrees C and between 22 and 25 GPa. The estimated decomposition curve for g-C3N4 has a positive slope (similar to 0.05 GPa/K) up to similar to 22 GPa, but becomes inverted (negative) above this pressure. The diamond formed through decomposition is characterized by euhedral crystals which are not sintered to each other, but loosely aggregated, suggesting the crystallization in a liquid (nitrogen) medium. The nitrogen release from the graphitic C - N framework may also play an important role in lowering the activation energy required for diamond formation and enhancing the grain growth rate. No phase transition of g-C3N4 was found in the studied P-T range. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.diamond.2011.03.034

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

Two new high-pressure phases of LiGaO2 have been discovered by direct compression of orthorhombic wurtzite-type LiGaO2 at pressures between 7 and 22 GPa and the temperatures of 25-2000 degrees C by means of the multianvil apparatus. The new intermediate phase recovered above 13 GPa at room temperature has been determined as a cation-disordered tetragonal structure with lattice parameters a=0.287 63(36) nm and c=0.419 29(117) nm, space group I4/m. The new high-pressure phase recovered above 16 GPa and 1400 degrees C has been refined as a cation-disordered cubic structure with lattice parameter of a=0.411 34(16) nm, space group Fm-3m. Powder x-ray diffraction and Raman scattering spectra observations reveal that besides the previously described polymorphic hexagonal phase, the tetragonal and cubic new phases of LiGaO2 are found to have rocksalt-related structures. Their structures can be labeled as layered-rocksalt- type, deformed-rocksalt- type, and disordered-rocksalt-type, respectively. The relationships between polymorphs of LiGaO2 provide some new insights into the pathways of ternary wurtzite-type semiconductors under high pressure. (C) 2010 American Institute of Physics. [doi:10.1063/1.3487976]

DOI： 10.1063/1.3487976

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

Phase transitions and the chemical composition of minerals in Earth's interior influence geophysical interpretations of its deep structure and dynamics. A pressure-induced spin transition in olivine has been suggested to influence iron partitioning and depletion, resulting in a distinct layered structure in Earth's lower mantle. For a more realistic mantle composition (pyrolite), we observed a considerable change in the iron-magnesium partition coefficient at about 40 gigapascals that is explained by a spin transition at much lower pressures. However, only a small depletion of iron is observed in the major high-pressure phase (magnesium silicate perovskite), which may be explained by preferential retention of the iron ion Fe3+. Changes in mineral proportions or density are not associated with the change in partition coefficient. The observed density profile agrees well with seismological models, which suggests that pyrolite is a good model composition for the upper to middle parts of the lower mantle.

DOI： 10.1126/science.1181443

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

Attempts have been made to synthesize nano-polycrystalline diamond (NPD) from graphite at pressures of 12, 13 and 14 GPa at temperatures 2200-2600°C using multi-anvil apparatus. The lower temperature limit for NPD formation increased with decreasing pressure, and we found that pure NPD can be synthesized even at the lowest pressure of 12 GPa, although quite high temperatures of exceeding 2600°C are required. This result demonstrates that NPD can be formed at significantly lower pressures than ever synthesized, which should provide an important constraint in synthesizing larger NPD samples under limited press loads. © 2010 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/215/1/012136

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

Pressure calibration experiments were performed at room temperature for a Drickamer-type apparatus using a composite anvil system with a sintered diamond anvil, which can be replaced by nano-polycrystalline diamond anvil. The culet diameter and tapering angle are 1.0 mm and 30°, respectively. Transitions in Fe2O3 (50 GPa) and CoO (55 GPa) were observed at 39.6 and 38.5 kN, respectively, by electrical resistance measurements. Pressure of about 120 GPa can be generated at the maximum load of 98 kN by assuming the linear extrapolation of the obtained load-pressure relation. The Drickamer-type apparatus with nano-polycrystalline diamond anvils has potential to generate pressure covering the whole lower mantle. © 2010 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/215/1/012189

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

The effect of chemical environment on the hydrogen-related defect chemistry in wadsleyite was investigated using Fourier-transform infrared (FTIR) spectroscopy. Samples were annealed at P = 14-16 GPa and T = 1230-1973 K using Kawai-type multi-anvil apparatus. The effect of oxygen fugacity (f(O2)) was investigated using three metal-oxide buffers (Mo-MoO2, Ni-NiO, and Re-ReO2)The effect of water fugacity (f(H2O)) was studied using two different capsule assemblies ("nominally dry" and "dry" assemblies). A range of total OH concentration (C-OH,(Total)) of studied wadslyeites varies between <50 H/10(6)Si (<3 wt ppm H2O) and 23 000 H/10(6)Si (1400 wt ppm H2O). The observed FTIR spectra were classified into four different classes, i.e., peaks at 3620 ("3620"), 3480 ("3480"), and 3205 cm(-1) ("3205") and the others (Group O), where the Group O includes peaks at 3270, 3330, and 3580 cm(-1). The variation in OH concentration corresponding to each peak was analyzed separately. The OH concentrations correspond to "3620," "3480," and "3205" were found to be highly dependent on both f(H2O) and f(O2). Assuming C-OH,(Group) (O) = 2[(2H)(M)(x)] (C-OH,(Group) (O) is OH concentration of Group O), present data were analyzed by using thermodynamic model for concentration of hydrogen-related defects. Based on analytical results, OH concentration of "3620" and "3480" was found to be reasonably explained by q = 1/2 and r = 1/12 (q and r are f(H2O) and f(O2) exponents, respectively), whereas that of "3205" was consistent with q = 1/2 and r = -1/12. These results suggest that "3620" and "3480" correspond to H whereas "3205" corresponds to H center dot, respectively, under the charge neutrality condition of [Fe-M(')] = 2[V-M(")].

DOI： 10.2138/am.2008.2653

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

A thermal equation of state of phase D with a Mg1.02Si1.73H3.03O6 composition has been derived from in situ X-ray diffraction experiments using synchrotron radiation and multianvil apparatus with sintered diamond anvils at pressures up to 46 GPa and temperatures up to 1300 K. The refined unit-cell parameters at ambient conditions are: a = 4.7643(7)angstrom, c = 4.346(2)angstrom, and V-0 = 85.43(4)angstrom(3) and the zero-pressure density of rho(0) = 3.357(2) g/cm(3) (Z = 1; formula weight = 172.70 g/mol). At room temperature, the unit-cell parameters show anisotropic compression behavior up to similar to 35 GPa, where the c-axis is more compressible than the a-axis. Above 35 GPa, however, the c-axis becomes less compressible than the a-axis. This change of the axial compression behavior tends to start at higher pressure with increasing temperature. The change of the linear compressibilities may be related to the hydrogen-bond symmetrization in phase D, as suggested by recent first-principles calculations.

DOI： 10.1080/08957950802246514

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担当区分：最終著者   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  

In this report, we discuss the progress in synthesis of new binary phases from B-C-N triangle in DAC under high-pressure and high-temperature (HPHT) conditions: cubic C3N4 (c-C3N4) and diamond-like BC3 (d-BC3) phase. These two phases have been synthesized by direct transformation from graphitic phases under HPHT conditions. The c-C3N4 phase was recovered at ambient conditions from the graphite-like C3N4 (g-C3N4) phase subjected to pressures between 21 and 38 GPa in a diamond anvil cell, laser-heated to temperatures between 1600 and 3000 K. The x-ray diffraction data on the new phase are best explained by a cubic unit cell with the lattice parameters a = 3.878±0.001 Å. The synthesis of the c-C3N4 phase has been also conducted in a large volume press at pressure 25 GPa and temperature 2000°C. X-ray peaks of c-C3N4 phase obtained in the large-volume press are weaker than those of diamonds. Application of the UV Raman spectroscopy revealed that UV Raman spectrum of the g-C3N4 is substantially different from that measured with visible Raman spectroscopy. It has two strong peaks at 690 cm-1 and at 986 cm -1 assigned to different types of the ring (s-triazine ring) breathing modes. A diamond-like BC3 has been synthesized at temperature 2033 ± 241 K and at pressure 50 GPa. The conclusion about the phase transition from graphitic BC3 (g-BC3) to d-BC3 phase was made from the analysis of Raman scattering data. The Raman spectrum of the novel d-BC3 displays all the peaks but one at 671 cm-1 characteristic to Raman spectra the B doped diamond. The peaks pattern of the d-BC3 suggests that this phase could become a superconductor at low temperatures. © 2008 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/121/6/062002

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

Precise density changes across 660 km seismic discontinuity have been determined for pyrolite and mid-oceanic ridge basalt (MORB) compositions at 1873 K at high pressures using a combination of in situ X-ray diffraction on unit cell measurements and chemical composition analyses on the recovered products, using a multiple sample chamber cell assembly. Density jump for the post-spinel transformation in pyrolite was determined to be similar to 9%, which is comparable to that of PREM. The density of MORB is found to be lower than that of pyrolite at the depths of similar to 590-680 km (using Anderson's equation of state for Au), however, it becomes denser than the pyrolite below similar to 680 km. The density cross-over region at similar to 590-680 km may contribute to the stagnation of subducted slabs near the similar to 660 km discontinuity, as suggested by seismological observations as well as earlier experimental studies based on quench experiments and extrapolated in situ X-ray measurements.

DOI： 10.1080/08957950802251357

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

To obtain higher pressures in a Kawai-type apparatus, we explored and tested high-pressure cell assemblies suitable for experiments using sintered diamond (SD) anvils. As a result, we succeeded in generating pressures exceeding 55 GPa at temperatures of 1000 degrees C in a Kawai-type apparatus (SPEED Mk-II) at SPring-8. Using the optimized cell assembly, we examined the stability field of MnGeO3 perovskite, an analog of MgSiO3 perovskite, which was recently found to transform to a new high-pressure form under the P-T conditions near the core-mantle boundary. From our in situ X-ray observations, MnGeO3 perovskite was found to be stable at pressures up to 56-57 GPa at temperatures of 800-1050 degrees C.

DOI： 10.2138/am.2006.2175

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

The phase boundary between wadsleyite and ringwoodite in Mg2SiO4 has been determined in situ using a multi-anvil apparatus and synchrotron X-rays radiation at SPring-8. In spite of the similar X-ray diffraction profiles of these high-pressure phases with closely related structures, we were able to identify the occurrence of the mutual phase transformations based on the change in the difference profile by utilizing a newly introduced press-oscillation system. The boundary was located at similar to 18.9 GPa and 1,400 degrees C when we used Shim's gold pressure scale (Shim et al. in Earth Planet Sci Lett 203:729-739, 2002), which was slightly (similar to 0.8 GPa) lower than the pressure as determined from the quench experiments of Katsura and Ito (J Geophys Res 94:15663-15670, 1989). Although it was difficult to constrain the Clapeyron slope based solely on the present data due to the kinetic problem, the phase boundary [P (GPa)=13.1+4.11x10(-3)xT (K)] calculated by a combination of a P-T position well constrained by the present experiment and the calorimetric data of Akaogi et al. (J Geophys Res 94:15671-15685, 1989) reasonably explains all the present data within the experimental error. When we used Anderson's gold pressure scale (Anderson et al. in J Appl Phys 65:1535-1543, 1989), our phase boundary was located in similar to 18.1 GPa and 1,400 degrees C, and the extrapolation boundary was consistent with that of Kuroda et al. (Phys Chem Miner 27:523-532, 2000), which was determined at high temperature (1,800-2,000 degrees C) using a calibration based on the same pressure scale. Our new phase boundary is marginally consistent with that of Suzuki et al. (Geophys Res Lett 27:803-806, 2000) based on in situ X-ray experiments at lower temperatures (&lt; 1,000 degrees C) using Brown's and Decker's NaCl pressure scales.

DOI： 10.1007/s00269-005-0053-y

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

In situ X-ray diffraction study was conducted to identify the crystal structure of the "Al-phase", which was previously reported to form in basaltic compositions at pressures and temperatures of the uppermost part of the lower mantle. Le Bail whole-pattern fitting method was adopted to investigate the structure of the Al-phase under high pressure and temperature as well as ambient conditions. Observed patterns were satisfactorily fitted using the "hexagonal phase" with space group P6(3)/m (plus minor amount of garnet) under both of these conditions. On the other hand, the calcium ferrite structure model proposed in some earlier studies based on quench experiments yielded profile-fitting results at significantly lower confidence levels, particularly at simultaneous high pressure and high temperature conditions, suggesting that this phase may not form in oceanic crust materials subducted in the uppermost lower mantle. The difference in densities of hexagonal and calcium ferrite phases, however, is only similar to 1% under pressures and temperatures of the uppermost part of the lower mantle conditions, which yields a negligible effect on the bulk density of the subducted oceanic crust.

DOI： 10.1007/s00269-005-0043-0

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

Grain-growth kinetics in wadsleyite was investigated using a multianvil high-pressure apparatus. Fine-grained wadsleyite aggregates gates were synthesized by isostatic hot-pressing and were subsequently annealed under high pressure and temperature in a controlled chemical environment. Wadsleyite samples show normal grain-growth characterized by a log-normal grain-size distribution following the relation, L-n - L-0(n) = kt where it is a constant, L the grain-size at time t, L-0 the grain-size at time t = 0 and k is a rate constant that depends on temperature T and chemical environments (f(O2): oxygen fugacity in Pa, C-OH: water content in H/10(6)Si) as:
k=A'(D)f(O2)'(D) exp (-H-D*/RT) + A'wf'(w)(O2) C-OH(q) exp (-H-w*/RT)
with A'(-4.9 +/- 6.1(-8.0 +/- 7.4))(D) (m(n) s(-1) Pa-rD), r(D) = 0.12 +/- 0.11 (0.20 +/- 0.14), h(D)* = 410 +/- 230(500 +/- 270) U/mol, A'(w)= 10(-18.2 +/- 1.4(-24.0 +/- 1.7)) (m(n) s(-1) Pa-rw), r(W), = 0.14 +/- 0.05(0.22 +/- 0.06), q = 1.7 +/- 0.3(2.2 +/- 0.3) and H-W* = 120 +/- 60(160 +/- 70) KJ/mol with assumed value of n = 2(3) (values in parentheses denote parameters for it = 3). Both water and oxygen fugacities significantly enhance grain-growth kinetics. The large value of the parameter describing the water fugacity dependence, q similar to 1.5-2.5, cannot be explained solely by a simple model in which grain-growth is controlled by diffusion of atoms (defects) across the grain-boundaries The interaction of grain-boundaries with charged defects or the density of hydrated ledges may be important factors that control the grain-growth kinetics of wadsleyite. When compared at similar thermo-chemical conditions, grain-growth of wadsleyite is found to be more sluggish than grain-growth of olivine. The present results show that a small wadsleyite grain-size (&lt; 1 mm) in subducting slabs can be maintained for a significant geological time (similar to 1 My) under "dry" (&lt; 200 H/10(6)Si) conditions when the temperature is lower than 1500 K, whereas when a large amount of water (&gt; 100,000 H/10(6)Si) is present, a small grain-size (&lt; 1 mm) can only be maintained for a significant time at low temperatures (&lt; 600 K). (c) 2005 Elsevier B.V All rights reserved.

DOI： 10.1016/j.pepi.2005.08.002

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

Thermal equation of state of an Al-rich phase with Na1.13Mg1.51Al4.47Si1.62O12 composition has been derived from in situ X-ray diffraction experiments using synchrotron radiation and a multianvil apparatus at pressures up to 24 GPa and temperatures up to 1,900 K. The Al-rich phase exhibited a hexagonal symmetry throughout the present pressure - temperature conditions and the refined unit-cell parameters at ambient condition were: a = 8.729(1) angstrom, c= 2.7695(5) angstrom, V-0 = 182.77(6) angstrom(3) (Z = 1; formula weight = 420.78 g/mol), yielding the zero-pressure density rho(0) = 3.823(1) g/cm(3). A least-square fitting of the pressure-volume-temperature data based on Anderson&apos;s pressure scale of gold ( Anderson et al. in J Appl Phys 65: 1534 - 543, 1989) to high-temperature Birch-Murnaghan equation of state yielded the isothermal bulk modulus K-0 = 176(2) GPa, its pressure derivative K-0&apos; = 4.9(3), temperature derivative (partial derivative K-T/partial derivative T)(P) = - 0.030(3) GPa K-1 and thermal expansivity alpha(T) = 3.36(6) x 10(-5) + 7.2(1.9) x 10(-9) T, while those values of K-0 = 181.7(4) GPa, (partial derivative K-T/partial derivative T)(P) = -0.020(2) GPa K-1 and alpha(T) = 3.28(7) x 10(-5) + 3.0(9) x 10(-9) T were obtained when K-0&apos; was assumed to be 4.0. The estimated bulk density of subducting MORB becomes denser with increasing depth as compared with earlier estimates ( Ono et al. in Phys Chem Miner 29: 527 - 531 2002; Vanpeteghem et al. in Phys Earth Planet Inter 138: 223 - 230 2003; Guignot and Andrault in Phys Earth Planet Inter 143 44: 107 - 128 2004), although the difference is insignificant (&lt; 0.6%) when the proportions of the hexagonal phase in the MORB compositions ( similar to 20%) are taken into account.

DOI： 10.1007/s00269-005-0029-y

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

[1] Phase relations of the olivine-wadsleyite transition in the system (Mg, Fe)(2)SiO4 have been determined at 1600 and 1900 K using the quench method in a Kawai-type high-pressure apparatus. Pressure was determined at a precision better than 0.2 GPa using in situ X-ray diffraction with MgO as a pressure standard. The transition pressures of the end-member Mg2SiO4 are estimated to be 14.2 and 15.4 GPa at 1600 and 1900 K, respectively. Partition coefficients for Fe and Mg between olivine and wadsleyite are 0.51 at 1600 K and 0.61 at 1900 K. By comparing the depth of the discontinuity with the transition pressure, the temperature at 410 km depth is estimated to be 1760 +/- 45 K for a pyrolitic upper mantle. The mantle potential temperature is estimated to be in the range 1550-1650 K. The temperature at the bottom of the upper mantle is estimated to be 1880 +/- 50 K. The thickness of the olivine-wadsleyite transition in a pyrolitic mantle is determined to be between 7 and 13 km for a pyrolitic mantle, depending on the efficiency of vertical heat transfer. Regions of rapid vertical flow ( e. g., convection limbs), in which thermal diffusion is negligible, should have a larger transition interval than stagnant regions, where thermal diffusion is effective. This is in apparent contradiction to short-period seismic wave observations that indicate a maximum thickness of &lt;5 km. An upper mantle in the region of the 410 km discontinuity with about 40% olivine and an Mg# of at least 89 can possibly explain both the transition thickness and velocity perturbation at the 410 km discontinuity.

DOI： 10.1029/2003JB002438

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

The phase boundary of the post-spinel transition in Mg2SiO4 was re-investigated by means of high P-T in situ X-ray diffractometry with a gold pressure marker in a Kawai-type apparatus. Rapid and continuous temperature changes were conducted to initiate dissociation of spinel, which tends to be inert after long annealing. Isothermal decompression at high temperature was conducted to form spinel from perovskite plus periclase. The phase boundary is located at ca. 22 GPa in the temperature range from 1550 to 2100 K, which is 1-1.5 GPa lower than the 660 km discontinuity. This discrepancy might be explained in terms of the pressure effect of thermocouple emf and inaccurate equation of state (EOS) for the pressure maker. The transition is found to be less sensitive to temperature than reported previously, with a Clapeyron slope ranging from -2 to -0.4 MPa/K. This small Clapeyron slope implies that the post-spinel transition would not be an effective barrier to mantle convection. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0031-9201(03)00019-0

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Stability relations of iron have been studied by means of in situ X-ray observations using an eight cubic anvil system (Kawai-type apparatus) equipped with sintered diamond (SD), in order to explore the stability of β-iron. By observing the forward and reverse transitions, it has been confirmed that ε-iron directly transforms into γ phase up to ca. 44 GPa and 2100 K, excluding the stability of β phase. The constrained ε-γ phase boundary is expressed by the equation T (K) = 25 x P (GPa) + 540.

DOI： 10.1029/2002GL016394

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掲載種別：研究論文（学術雑誌）  

Large discrepancies are reported for the near-solidus, pressure-temperature location of the spinel to garnet lherzolite univariant curve in the system CaO-MgO-Al2O3-SiO2 (CMAS). Experimental data obtained previously from the piston-cylinder apparatus indicate interlaboratory pressure differences of up to 30% relative. To investigate this disparity-and because this reaction is pivotal for understanding upper mantle petrology-the phase boundary was located by means of an independent method. The reaction was studied via in situ X-ray diffraction techniques in a 6-8 type multianvil press. Pressure is determined by using MgO as an internal standard and is calculated from measured unit cell volume by using a newly developed high-temperature equation of state for MgO. Combinations of real-time and quenched-sample observations are used to bracket the phase transition. The transition between 1350 and 1500°C was reversed, and the reaction was further constrained from 1207 to 1545°C. Within this temperature range, the transition has an average dT/dP slope of ∼40 ± 10°C/kbar, consistent with several previous piston-cylinder studies. Extrapolation of our curve to 1575°C, an established temperature of the P-T invariant point, yields a pressure of 25.1 ± 1.2 kbar. We also obtained a real-time reversal of the quartz-coesite transition at 30.5 ± 2.3 kbar at 1357°C, which is about 2 to 4 kbar lower in pressure than previously determined in the piston-cylinder apparatus. Copyright © 2002 Elsevier Science Ltd.

DOI： 10.1016/S0016-7037(02)00845-1

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

Crystal structures and phase transitions of enstatite (MgSiO3) were studied by in situ X-ray diffraction experiments using synchrotron radiation and a multi-anvil high-pressure apparatus at presures to 12 GPa and temperatures to 1473 K. Low clinoenstatite with space group P21/c transforms to high-pressure C2/c clinoenstatite at high pressures and high temperatures, accompanied by a volume reduction of about 2.5%. The β angle of this high-pressure C2/c phase ranges from 101.4°to 101.7°, shows almost no variation with pressure and temperature, and is about 8°smaller than that of the high-temperature C2/c phase previously reported. This confirms the suggestion (Hugh-Jones et al. 1994) that these two clinoenstatite phases differ at high pressures and high temperatures. The pressure-volume-temperature data for P21/c and high pressure C2/c clinoenstatite were fit to room-temperature third-order Birch-Murnahan equations of state (EOS) using the parameters: volume of V0 = 415.4 (5) Å3, isothermal bulk modulus of K0 = 108.5 (6.4) GPa, and its pressure derivative of K'0=4.5 (1.3) for the P21/c phase, and V0 = 405.1 (1.7) Å3, K0 = 106.4 (17.4) GPa, and K'0 = 5.4 (2.7) for the C2/c phase. These values are at ambient conditions. For the C2/c phase, we determined the high-temperature EOS, expressed as P = 3/2 K(T) [(V(T)/V)(7/3)-(V(T)/V)(5/3)]{1-3/4 (4-K'(T)[V(T)/V)(2/3)-1]}, where K(T) = K0 + (partial differential K(T)/partial differential T)(P) (T-300), K'(T) = K'0, V(T) = V0 [exp(∫300(T) α(T)dT)], where thermal expansivity α(T) is a0 + a1 T. The parameters are V0 = 405.0 (2.6) Å3, K0 = 106.9 (25.9) GPa, K'0 = 5.3 (3.9), a0 = 2.01 (44) x 10-5 K-1, a1 = 2.10 (1.1) x 10-8 K-2, and (partial differential K(T)/partial differential T)(P) = -0.021 (10) GPa/K. Although the K0 values are nearly the same with those of previous studies for both the P21/c and C2/c phases, the K'0 values are slightly smaller.

DOI： 10.2138/am-1999-1012

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

X ray diffraction and transmission electron microscopy on laser-heated diamond cell samples show that with increasing pressure MgAl2O4 spinel, transforms first to Al2O3 corundum + MgO periclase, then to the CaFe2O4-structured phase, and finally to a new phase having the CaTi2O4 structure above similar to 40 GPa. The CaFe2O4 and the CaTi2O4 structures are closely related and have almost the same densities and bulk moduli. Transformation from the CaFe2O4 to the CaTi2O4 phase would be expected to take place in oceanic crust that is subducted deep into the lower mantle.

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

In experiment at 13.5 gigapascals and 1030°C, the growth rate of wadsleyite, which forms from transformation of olivine, was substantially enhanced by the presence of water. Wadsleyite had a low dislocation density and subgrain boundaries in wet runs. Water enhanced the dislocation recovery in wadsleyite and therefore caused inelastic relaxation of the localized pressure drop associated with the transformation, resulting in an increase of the growth rate in wet runs. These results imply that even a small amount of water of 0.05 weight percent can weaken wadsleyite in the mantle.

DOI： 10.1126/science.281.5373.85

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Single crystalline San Carlos olivine (1 mm cube) was transformed to (Mg,Fe)2SiO4 β-phase at 13.5-15 GPa, 1030-1330 °C for 0-600 min using a multi-anvil high pressure apparatus. The α-β transformation occurred by incoherent surface nucleation and interface-controlled growth and recovered partially transformed samples showed sharply defined reaction rim. The growth rate of the β-phase rim significantly decreased with time and the growth eventually ceased. TEM observations revealed that many dislocations were created in both the relict olivine just near the α-β interface and the β-phase in the rim, which show evidence for deformation caused by interfacial stresses associated with the misfit elastic strain of the transformation. The observed tangled dislocation texture in β-phase suggested that the β-phase rim was hardened and relaxation of the interfacial stress was retarded. This probably caused a localized pressure drop in the relict olivine and decreased the growth rate. Time-dependent growth rates of β-phase is possibly controlled by the rheology of β-phase, which must be considered for the prediction of the olivine metastability in the subducting slabs.

DOI： 10.1007/s002690050155

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記述言語：日本語   出版者・発行元：一般社団法人 日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本地球化学会  

&lt;p&gt;地球深部での窒素の化学状態や存在量は明らかでなく、地球全体での窒素のbudgetを考える上でもマントル鉱物への窒素の取り込みを実験的に明らかにすることは重要である。本研究でマルチアンビル型高圧発生装置を利用して高温高圧実験を行い、NanoSIMSをによる回収試料の窒素の検出を試みた。bridgmaniteからも共存相として析出したstishoviteからも窒素が検出された。AlとHと窒素濃度との関連はまだ明らかではないが、ホスト鉱物中の欠陥形成と関連して窒素濃度に影響を及ぼしている可能性はある。&lt;/p&gt;

DOI： 10.14862/geochemproc.64.0_252

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記述言語：日本語   出版者・発行元：一般社団法人日本地球化学会  

<p>地球深部での窒素の化学状態や存在量は明らかでなく、地球全体での窒素のbudgetを考える上でもマントル鉱物への窒素の取り込みを実験的に明らかにすることは重要である。本研究でマルチアンビル型高圧発生装置を利用して高温高圧実験を行い、NanoSIMSをによる回収試料の窒素の検出を試みた。bridgmaniteからも共存相として析出したstishoviteからも窒素が検出された。AlとHと窒素濃度との関連はまだ明らかではないが、ホスト鉱物中の欠陥形成と関連して窒素濃度に影響を及ぼしている可能性はある。</p>

DOI： 10.14862/geochemproc.64.0_252

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

マルチアンビル装置を用いた高温高圧合成法により得られた、グロシュラーを中心としたナノ多結晶ガーネット試料の可視光領域での透光性、TEM観察、硬度測定などをおこなった。この結果、ナノ多結晶グロシュラーが可視光領域で単結晶に匹敵する透光性を有することや、単結晶に比べて３０％程度硬度が高いことが明らかになった。超高圧を利用した本手法は、従来困難であった透明ナノセラミックスの合成に道をひらいたといえる。

DOI： 10.14824/jakoka.2016.0_104

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The strength of Polycrystalline Diamond (PCD) was investigated through a high Pressure (P) and Temperature (T) deformation experiment. Two samples were sintered back to back under identical conditions and shared identical initial grain size distribution. One sample (4.4a) had lower concentration of crystalline defects than the other (3.4a). In crushing strength tests conducted prior to the deformation experiment, 4.4a exhibited an enhanced crushing strength compared to 3.4a. During the high P-T deformation experiment, the samples were stacked and deformed together and their mechanical properties were investigated in situ using synchrotron Xray diffraction and imaging. The strain data based on imaging showed that the two samples were deformed at the same rate (ca. 1.5 × 10-5 s-1). Analysis of the diamond lattice plane distortions in the diffraction patterns showed that sample 4.4a exhibits slightly greater strength, especially towards large amounts of strain. We interpret this difference as due to a better sintering for 4.4a, thanks to lower defect concentration and cleaner grain surfaces of the precursor powder, which results into stronger diamond-diamond bonding. These data suggest that the use of diamond grains with reduced defect concentration and cleaner surfaces as a precursor improves the bulk strength and the wear resistance of the resulting PCD.

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

マルチアンビル装置を用いた高温高圧合成法により、グロシュラー及びパイロープガーネットのナノ多結晶体の合成をおこなった。ドライ条件下でのガラスを出発物質として用い、圧力15GPa・温度1300～1400℃付近の条件下で粒形100nm程度以下のナノ多結晶の焼結体が得られた。得られた焼結体は極めて透光性が高く、弾性波測定等の物性測定試料としても最適である。

DOI： 10.14824/jakoka.2015.0_111

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

マルチアンビル高圧装置を用いて、高温高圧下での高品質高圧相多結晶体の合成を試みた。特にアルマンディン、パイロープ、グロシュラーなどの上部マントルにおいて主要なガーネット多結晶体の合成を行い、サブミクロン～数ミクロン程度の粒径からなる透光性の高い多結晶ガーネットを得ることに成功した。これらの高品質多結晶ガーネットは、超音波法やブリルアン散乱法による弾性波速度測定など、様々な物性測定において重要な試料になると期待される。

DOI： 10.14824/jakoka.2014.0_82

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

マルチアンビル高圧装置を用いて、高温高圧下での高品質高圧相多結晶体の合成を試みた。特にアルマンディン、パイロープ、グロシュラーなどの上部マントルにおいて主要なガーネット多結晶体の合成を行い、サブミクロン～数ミクロン程度の粒径からなる透光性の高い多結晶ガーネットを得ることに成功した。これらの高品質多結晶ガーネットは、超音波法やブリルアン散乱法による弾性波速度測定など、様々な物性測定において重要な試料になると期待される。

DOI： 10.14824/jakoka.2014.0_82

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記述言語：日本語   出版者・発行元：日本鉱物科学会  

下部マントル条件での鉄のスピン転移が，構成相間の鉄の分配とぺロブスカイトーポストペロブスカイト相転移圧にどう関係しているかを，我々のスピン転移の実験結果とこれまでの鉄の分配および相転移圧に関する報告に基づいて考察する．

DOI： 10.14824/jakoka.2011.0.225.0

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DOI： 10.14824/jakoka.2010.0.116.0

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

愛媛大学地球深部ダイナミクスセンターでは、2009年に現在世界最大となる川井式マルチアンビル超高圧合成装置を導入した。本発表では、この装置の概要を報告するとともに、圧力および温度発生の現状について報告する。また、この装置を用いた研究の例として、大型超硬硬度ナノダイヤモンド（NPD=ヒメダイヤ）合成の現状と、今後の課題についても述べる予定である。

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DOI： 10.14824/jakoka.2009.0.187.0

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

焼結ダイヤモンドアンビルを用いたマルチアンビル装置により、50GPa程度の圧力下までのパイロライト組成の相関係・元素分配・密度変化を、X線その場観察および急冷回収試料の分析によりおこなった。また、得られた試料のいくつかにおいて、主要相であるMgペロフスカイトおよびマグネシオウスタイトのFeの価数をメスバワー分光およびEELSにより決定した。これら２相の間のFe分配は40GPa程度を境に大きく変化することが見い出されたが、これはマグネシオウスタイト中の2価Feの相対的濃集により説明でき、Feの高スピン-低スピン転移に関連づけられる。またパイロライトの密度は地震学的モデルと良く一致し、下部マントルの化学組成として適切であることが示された。

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

下部マントルの最大構成相であるMg-ペロブスカイト中の鉄の高圧下におけるスピン状態を調べるため，(Mg0.85Fe(3+)0.15)(Al0.15Si0.85)O3 組成の合成ペロブスカイト中の３価鉄について，Ｘ線発光分光法により 室温下200 GPa までの高圧下のスピン状態を測定した．測定にはダイヤモンドアンビルセルを用い，スプリングー８のBL-12で鉄のk-beta&#039; のX線発光スペクトルを測定した． 測定の結果，Mg-ペロブスカイト中の３価鉄のスピン状態は，圧力の増加に伴い120 GPa あたりからスピン数が減少し，200 GPa では high spin とlow spin の中間状態になったが，low spin にはならなかった．これらの結果からすると，下部マントルでのMg-ペロブスカイト中の３価鉄のスピン状態は，スピン転移が正の温度勾配を持つとすると，low spin にはならないと推定される．

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

我々のグループではマルチアンビル装置を用いた高温高圧下におけるグラファイトの直接変換により、極めて高い硬度を有するナノサイズの立方晶ダイヤモンド多結晶体（NPD=ヒメダイヤ）の合成を2003年に報告した。その後NPDの大型化と良質化に取り組み、また6000トン駆動の大型マルチアンビル装置の導入により、現在までに直径・長さともに7mm程度の円柱型試料の合成が可能になった。講演ではこのように合成されたNPDの特性や、その超高圧発生への応用について報告する

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記述言語：日本語   出版者・発行元：公益社団法人 日本セラミックス協会  

我々のグループでは、マルチアンビル型装置を用いて高温高圧下における直接変換法により、グラファイトを出発物質を用いた多結晶ダイヤモンド焼結体の合成に成功し2003年にネイチャー誌に発表した。この焼結体はナノサイズのダイヤモンド集合であり、単結晶ダイヤモンドと同等以上の硬さを持つことも明らかになった。我々はこのナノ多結晶ダイヤモンド（NPD）の特性解明とともに、その良質化や大型化に取り組み、超高圧発生装置等への応用を試みつつある。本講演ではNPDの微細組織構造、硬度や弾性・光学特性、またその応用に関して総合的に報告する。

DOI： 10.14853/pcersj.2009F.0.1G01.0

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記述言語：日本語   出版者・発行元：公益社団法人 日本セラミックス協会  

我々のグループでは、マルチアンビル型装置を用いて高温高圧下における直接変換法により、グラファイトを出発物質を用いた多結晶ダイヤモンド焼結体の合成に成功し2003年にネイチャー誌に発表した。この焼結体はナノサイズのダイヤモンド集合であり、単結晶ダイヤモンドと同等以上の硬さを持つことも明らかになった。我々はこのナノ多結晶ダイヤモンド（NPD）の特性解明とともに、その良質化や大型化に取り組み、超高圧発生装置等への応用を試みつつある。本講演ではNPDの微細組織構造、硬度や弾性・光学特性、またその応用に関して総合的に報告する。

DOI： 10.14853/pcersj.2009F.0.1G01.0

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DOI： 10.14824/jakoka.2009.0.150.0

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

下部マントルの最大構成相であるMg-ペロブスカイト中の鉄の高圧下におけるスピン状態を調べるため，(Mg0.85Fe(3+)0.15)(Al0.15Si0.85)O3 組成の合成ペロブスカイト中の３価鉄について，Ｘ線発光分光法により 室温下200 GPa までの高圧下のスピン状態を測定した．測定にはダイヤモンドアンビルセルを用い，スプリングー８のBL-12で鉄のk-beta' のX線発光スペクトルを測定した．
測定の結果，Mg-ペロブスカイト中の３価鉄のスピン状態は，圧力の増加に伴い120 GPa あたりからスピン数が減少し，200 GPa では high spin とlow spin の中間状態になったが，low spin にはならなかった．これらの結果からすると，下部マントルでのMg-ペロブスカイト中の３価鉄のスピン状態は，スピン転移が正の温度勾配を持つとすると，low spin にはならないと推定される．

DOI： 10.14824/jakoka.2009.0.182.0

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記述言語：日本語   出版者・発行元：日本鉱物科学会  

含水高圧鉱物（DHMS）の中で最も高圧まで安定なphase Dの安定性と高温圧縮特性を調べるため、焼結ダイヤモンドアンビルを使用したマルチアンビル高圧装置と放射光を組み合わせたX線その場回折実験を行った。実験条件は約28-46GPaの圧力範囲、温度1300Kまでの領域で行った。得られた回折パターンから格子定数を計算し、高温の状態方程式を導いた。

DOI： 10.14824/jakoka.2008.0.196.0

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

放射光X線回折，発光分光を用いて，FeAlO3を固溶した珪酸塩ペロブスカイトの圧縮率および鉄のスピン状態を測定した。珪酸塩ポストペロブスカイト中の3価鉄は約50GPaでスピン5/2のハイスピンであったが，約80-113GPaの圧力領域では中間スピン状態であった。体積および軸長は圧力の増加に伴いスムーズに減少し，大きな不連続は見いだせなかったが，体積弾性率は純粋なMgSiO3ペロブスカイトに比較して小さな値を示しており，スピン状態との関連が伺える。

DOI： 10.14824/jakoka.2008.0.194.0

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記述言語：日本語   出版者・発行元：日本鉱物科学会  

放射光X線回折，発光分光を用いて，FeAlO3を固溶した珪酸塩ペロブスカイトの圧縮率および鉄のスピン状態を測定した。珪酸塩ポストペロブスカイト中の3価鉄は約50GPaでスピン5/2のハイスピンであったが，約80-113GPaの圧力領域では中間スピン状態であった。体積および軸長は圧力の増加に伴いスムーズに減少し，大きな不連続は見いだせなかったが，体積弾性率は純粋なMgSiO3ペロブスカイトに比較して小さな値を示しており，スピン状態との関連が伺える。

DOI： 10.14824/jakoka.2008.0.194.0

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

Mg‐ペロブスカイトにおける３価鉄の圧力誘起スピン転移を調べるため，ダイヤモンドアンビルセルに封じたMg&lt;SUB&gt;0.85&lt;/SUB&gt;Fe&lt;SUP&gt;3+&lt;/SUP&gt;&lt;SUB&gt;0.15&lt;/SUB&gt;Al&lt;SUB&gt;0.15&lt;/SUB&gt;Si&lt;SUB&gt;0.85&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;組成のペロブスカイトをX線発光分光法により調べた．その結果，50-80 GPa でスピン状態が高スピンから中間スピンに変わり，その後113 GPa に至るまで中間的なスピン状態であった．こうしたある圧力幅での中間的なスピン状態は，ペロブスカイトのAサイトに３価鉄が入り，その歪んだドデカヘドラルサイトの結晶場によって生じると説明できる．

DOI： 10.14824/jakoka.2008.0.186.0

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記述言語：日本語   出版者・発行元：日本鉱物科学会  

Mg‐ペロブスカイトにおける３価鉄の圧力誘起スピン転移を調べるため，ダイヤモンドアンビルセルに封じたMg<SUB>0.85</SUB>Fe<SUP>3+</SUP><SUB>0.15</SUB>Al<SUB>0.15</SUB>Si<SUB>0.85</SUB>O<SUB>3</SUB>組成のペロブスカイトをX線発光分光法により調べた．その結果，50-80 GPa でスピン状態が高スピンから中間スピンに変わり，その後113 GPa に至るまで中間的なスピン状態であった．こうしたある圧力幅での中間的なスピン状態は，ペロブスカイトのAサイトに３価鉄が入り，その歪んだドデカヘドラルサイトの結晶場によって生じると説明できる．

DOI： 10.14824/jakoka.2008.0.186.0

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

含水高圧鉱物（DHMS）の中で最も高圧まで安定なphase Dの安定性と高温圧縮特性を調べるため、焼結ダイヤモンドアンビルを使用したマルチアンビル高圧装置と放射光を組み合わせたX線その場回折実験を行った。実験条件は約28-46GPaの圧力範囲、温度1300Kまでの領域で行った。得られた回折パターンから格子定数を計算し、高温の状態方程式を導いた。

DOI： 10.14824/jakoka.2008.0.196.0

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記述言語：日本語   出版者・発行元：日本鉱物科学会  

放射光X線その場観察実験により、パイロライトとMORBの660km地震波不連続面付近の密度変化を明らかにした。密度は高温高圧下における鉱物の格子体積と、回収試料の化学組成分析から、X線密度の定義に従って決定した。パイロライト、MORBともIrifune (1993)、Irifune and Ringwood (1993)の結果と一致した。Irifune (1993)では特に下部マントル領域における密度変化に大きな誤差が生じていた（約±0.1g/cm<SUP>3</SUP>）。これは、鉱物の化学組成分析、格子定数の誤差と、熱弾性パラメーターの不確定さに起因していた。本研究では、熱弾性パラメーターの誤差が加わらないため、約±0.05 g/cm<SUP>3</SUP>以下の精度で密度変化を制約することができた。

DOI： 10.14824/kobutsu.2005.0.18.0

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記述言語：日本語   出版者・発行元：日本鉱物科学会  

地球のマントルの代表的な組成と考えられているパイロライトについてマルチアンビル高圧装置と放射光を用いたその場X線回折実験を30-40GPa, 1800℃の領域で行った。その結果これまで報告されている30GPaまでの相関係に変化は見られず、Mg-rich perovskite, Ca-rich perovskite, (Mg,Fe)O ferropericlase が観察された。

DOI： 10.14824/kobutsu.2005.0.14.0

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出版者・発行元：日本鉱物科学会  

放射光X線その場観察実験により、パイロライトとMORBの660km地震波不連続面付近の密度変化を明らかにした。密度は高温高圧下における鉱物の格子体積と、回収試料の化学組成分析から、X線密度の定義に従って決定した。パイロライト、MORBともIrifune (1993)、Irifune and Ringwood (1993)の結果と一致した。Irifune (1993)では特に下部マントル領域における密度変化に大きな誤差が生じていた（約±0.1g/cm&lt;SUP&gt;3&lt;/SUP&gt;）。これは、鉱物の化学組成分析、格子定数の誤差と、熱弾性パラメーターの不確定さに起因していた。本研究では、熱弾性パラメーターの誤差が加わらないため、約±0.05 g/cm&lt;SUP&gt;3&lt;/SUP&gt;以下の精度で密度変化を制約することができた。

DOI： 10.14824/kobutsu.2005.0.18.0

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出版者・発行元：日本鉱物科学会  

地球のマントルの代表的な組成と考えられているパイロライトについてマルチアンビル高圧装置と放射光を用いたその場X線回折実験を30-40GPa, 1800℃の領域で行った。その結果これまで報告されている30GPaまでの相関係に変化は見られず、Mg-rich perovskite, Ca-rich perovskite, (Mg,Fe)O ferropericlase が観察された。

DOI： 10.14824/kobutsu.2005.0.14.0

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