研究者詳細 - 丹羽　健

論文 - 丹羽　健

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Lithium ionic conductivities of α-LiBO2 with two-dimensional Li-Li networks and γ-LiBO2 with three-dimensional ones synthesized under high pressure 査読有り

Hirose, E; Kataoka, K; Nagata, H; Akimoto, J; Sasaki, T; Niwa, K; Hasegawa, M

JOURNAL OF SOLID STATE CHEMISTRY 274 巻頁： 100 - 104 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Solid State Chemistry

Lithium ionic conductivities of two LiBO 2 polymorphs, i.e. the same composition Li borates: α-LiBO 2 and γ-LiBO 2 , which are ambient and high-pressure phases, have been measured by the AC impedance method between 450 and 520 K using their high-density polycrystalline samples synthesized under high pressures. It is found the intra-grain and total conductivities of the γ-LiBO 2 have been measured for the first time and be of the order 10 −5 ∼ 10 −6 Scm −1 and 10 −6 Scm −1 , respectively, both of which are higher in whole measured temperature range than those of the α-LiBO 2 . The higher lithium ionic conductivities of the former are discussed from the viewpoints of local structure and Li ion network in the crystal structures of the α-LiBO 2 and γ-LiBO 2 .

DOI： 10.1016/j.jssc.2019.02.045

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High-pressure synthesis, crystal growth, and compression behavior of hexagonal CrN2 having one-dimensionally aligned nitrogen dimer 査読有り

Niwa, K; Yamamoto, T; Sasaki, T; Hasegawa, M

PHYSICAL REVIEW MATERIALS 3 巻 ( 5 ) 2019年5月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review Materials

A hexagonal chromium pernitride, CrN2, has been successfully synthesized via a direct chemical reaction between chromium and molecular nitrogen at a pressure of approximately 70 GPa. The advanced synchrotron x-ray diffraction (XRD) measurements after recovery and structural refinement at 0.1 MPa demonstrated that CrN2 crystallizes in the anti-NiAs-type structure with lattice parameters of a=2.7465(3)Å and c=7.3670(4)Å. Micron-sized hexagonal habit compounds were found in the synthesized products, which indicated that the single crystal of hexagonal CrN2 was grown in the supercritical nitrogen at high pressure. High-pressure in situ XRD measurements were performed to determine the zero-pressure bulk modulus, K0, value of 286(6) GPa [K′0=2.5(7)] and remarkable incompressibility of the c axis. CrN2 is a unique example of the recoverable transition-metal pernitride which presents one-dimensionally aligned N-N dimers in the structure. The one-dimensionally aligned N-N dimers play an important role in controlling the mechanical and electronic properties of CrN2 as predicted by theoretical calculations.

DOI： 10.1103/PhysRevMaterials.3.053601

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Infrared spectroscopy on electronic structures of platinum-group metal pernitrides MN2 (M = Ru, Rh, Ir, and Pt) 査読有り

Soda, K; Komabuchi, M; Maeguchi, K; Kato, M; Terabe, T; Niwa, K; Hasegawa, M; Ikemoto, Y; Okamura, H

PHYSICA B-CONDENSED MATTER 558 巻頁： 54 - 58 2019年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physica B: Condensed Matter

The electronic structures of platinum-group metal pernitrides MN 2 (M = Ru, Rh, Ir, and Pt) were investigated via synchrotron radiation infrared spectroscopy and first-principles calculations. Measured reflectance spectra of marcasite-type RuN 2 and RhN 2 showed Drude-like responses, approaching 1 as the photon energy was decreased, whereas reflectance of arsenopyrite-type IrN 2 and pyrite-type PtN 2 became ∼0.3 in the low photon energy region with a few features. These findings agreed well with the predictions of the metallic nature of marcasite-type RuN 2 and RhN 2 and the semiconducting properties of arsenopyrite-type IrN 2 and pyrite-type PtN 2 , respectively. The measured reflectance spectra were also reasonably consistent with the calculated optical responses. The band gaps of IrN 2 and PtN 2 were estimated to be 0.8 and 2.1 eV, respectively, via first-principles calculation with a modified Becke–Johnson (MBJ) potential for the exchange potential.

DOI： 10.1016/j.physb.2019.01.017

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High-Pressure Synthesis, Crystal Chemistry, and Ionic Conductivity of a Structural Polymorph of Li3BP2O8 査読有り

Hirose, E; Kataoka, K; Nagata, H; Akimoto, J; Sasaki, T; Niwa, K; Hasegawa, M

INORGANIC CHEMISTRY 57 巻 ( 24 ) 頁： 15048 - 15050 2018年12月

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

A new structural polymorph of Li 3 BP 2 O 8 has been successfully synthesized via a solid-state reaction between Li 3 PO 4 and BPO 4 at 4 GPa and 600 °C. The high-pressure phase of Li 3 BP 2 O 8 (HP-Li 3 BP 2 O 8 ) was found to crystallize in monoclinic symmetry with the cell parameters of a = 8.57010(4) Å, b = 11.11812(5) Å, c = 5.55380(3) Å, and β = 97.7269(3)° [space group P2 1 /a (No. 14)]. HP-Li 3 BP 2 O 8 has a new crystal structure that has not been reported so far. The total ionic conductivities measured for the polycrystalline sample by alternating-currrent impedance were 3.4 × 10 -7 and 2.1 × 10 -6 S/cm at 399 and 456 K, respectively. The lithium ionic conductivity of HP-Li 3 BP 2 O 8 was higher than that of the low-pressure phase Li 3 BP 2 O 8 in the temperature range of 375-456 K. This is caused by the difference in the dimensions of the lithium arrangements between LP- and HP-Li 3 BP 2 O 8 .

DOI： 10.1021/acs.inorgchem.8b03155

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PubMed

Structural stability of the Li-ion conductor Li7La3Zr2O12 investigated by high-pressure in-situ X-ray diffraction and Raman spectroscopy

Hirose, E; Niwa, K; Kataoka, K; Akimoto, J; Hasegawa, M

MATERIALS RESEARCH BULLETIN 107 巻頁： 361 - 365 2018年11月

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

The high-pressure behavior of Li7La3Zr2O12 (LLZO) with a garnet-related structure has been investigated for the first time by high pressure in situ X-ray diffraction measurements and Raman spectroscopy using a diamond anvil cell. It was found that the tetragonal LLZO transforms to the high-pressure cubic phase (HP-c-LLZO) at 71.8 GPa in a N2 medium and at 25.8 GPa in the absence of pressure mediums. Uniaxial compression in the absence of pressure mediums induced the phase transition at much lower pressures than in the hydrostatic case when N2 was used as the pressure medium. High pressure in situ Raman spectroscopy suggested that the Li coordination in HP-c-LLZO was different from that reported in cubic LLZO, which had been stabilized by doping Al at ambient pressure and room temperature.

DOI： 10.1016/j.materresbull.2018.07.034

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Valence-Band Electronic Structures of High-Pressure-Phase PdF2-type Platinum-Group Metal Dioxides MO2 (M = Ru, Rh, Ir, and Pt)

Soda, K; Kobayashi, D; Mizui, T; Kato, M; Shirako, Y; Niwa, K; Hasegawa, M; Akaogi, M; Kojitani, H; Ikenaga, E; Muro, T

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 87 巻 ( 4 ) 2018年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Physical Society of Japan

The valence-band electronic structures of high-pressure-phase PdF2-type (HP-PdF2-type) platinum-group metal dioxides MO2 (M = Ru, Rh, Ir, and Pt) were studied by synchrotron radiation photoelectron spectroscopy and first-principles calculations. The obtained photoelectron spectra for HP-PdF2-type RuO2, RhO2, and IrO2 agree well with the calculated valence-band densities of states (DOSs) for these compounds, indicating their metallic properties, whereas the DOS of HP-PdF2-type PtO2 (calculated in the presence and absence of spin–orbit interactions) predicts that this material may be metallic or semimetallic, which is inconsistent with the electric conductivity reported to date and the charging effect observed in current photoelectron measurements. Compared with the calculated results, the valence-band spectrum of PtO2 appears to have shifted toward the high-binding-energy side and reveals a gradual intensity decrease toward the Fermi energy EF, implying a semiconductor-like electronic structure. Spin-dependent calculations predict a ferromagnetic ground state with a magnetization of 0.475 μB per formula unit for HP-PdF2-type RhO2

DOI： 10.7566/JPSJ.87.044701

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High pressure in-situ synthesis and physical properties of Cr3C2-Ni cermets 国際共著

Zhai, WY; Gao, YM; Sun, L; Wang, YR; Niwa, K; Hasegawa, M

CERAMICS INTERNATIONAL 43 巻 ( 18 ) 頁： 17202 - 17205 2017年12月

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

A novel Cr3C2-Ni cermets were successfully in-situ synthesized with Cr, C and Ni (20 wt%) mixed-powder at 1100 °C under 0–6 GPa isostatic pressure using a small-sized cubic-type multi-anvil press apparatus. High purity Cr3C2 phase was generated in the cermets. Comparing with the conventional and reactive sintering, the sintering temperature and the average grain size of Cr3C2 decreased by 200 °C and 50%, respectively. The physical properties, normalized lattice parameters and volumes of Cr3C2−20 wt%Ni cermet as a function of pressure had been studied both experimentally and by first-principles calculations for the first time.

DOI： 10.1016/j.ceramint.2017.09.145

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Pyrite form of group-14 element pernitrides synthesized at high pressure and high temperature

Niwa, K; Ogasawara, H; Hasegawa, M

DALTON TRANSACTIONS 46 巻 ( 30 ) 頁： 9750 - 9754 2017年8月

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

The chemical reaction of group-14 elements with molecular nitrogen at pressures above 60 GPa successfully leads to the formation of pyrite-type pernitrides. These new crystalline group-14 elemental pernitrides were found to show a bulk modulus higher than the other known group-14 elemental nitrides. Our results offer significant new progress in the solid-state chemistry of nitrides.

DOI： 10.1039/c7dt01583f

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PubMed

Microbeam Hard X-ray Photoemission Study on Platinum-Group Metal Pernitrides

Soda, K; Mizui, T; Komabuchi, M; Kato, M; Terabe, T; Suzuki, K; Niwa, K; Shirako, Y; Hasegawa, M; Akaogi, M; Kojitani, H; Ikenaga, E

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 86 巻 ( 6 ) 頁： 64804 - 64804 2017年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Physical Society of Japan

Using microbeam hard X-ray photoelectron spectroscopy, we clarified the valence-band electronic structures and chemical states of platinum-group metal (Ru, Ir, and Pt) pernitrides, which have been synthesized in supercritical nitrogen fluid under extremely high pressures and temperatures. Their nitrogen contents relative to the platinum-group metal are estimated to be 2 from the photoemission intensity, which is consistent with the studies reported to date. The observed valence-band structures agree quite well with theoretically predicted structures for the pyrite-type PtN2, arsenopyrite-type IrN2, and marcasite-type RuN2. The origin of their extremely large bulk moduli is discussed based on the current results of the valence-band structures and core-level chemical shifts.

DOI： 10.7566/JPSJ.86.064804

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CiNii Research

Highly Coordinated Iron and Cobalt Nitrides Synthesized at High Pressures and High Temperatures

Niwa, K; Terabe, T; Kato, D; Takayama, S; Kato, M; Soda, K; Hasegawa, M

INORGANIC CHEMISTRY 56 巻 ( 11 ) 頁： 6410 - 6418 2017年6月

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

Highly coordinated iron and cobalt nitrides were successfully synthesized via direct chemical reaction between a transition metal and molecular nitrogen at pressures above approximately 30 GPa using a laser-heated diamond anvil cell. The synthesized novel transition metal nitrides were found to crystallize into the NiAs-type or marcasite-type structure. NiAs-type FeN could be quenched at ambient pressure, although it was gradually converted to the ZnS-type structure after the pressure was released. On the other hand, CoN was recovered with ZnS-type structure through a phase transition from NiAs-type structure at approximately a few gigapascals during decompression. Marcasite-type CoN2 was also synthesized at pressures above approximately 30 GPa. High-pressure in situ X-ray diffraction measurement showed that the zero-pressure bulk modulus of marcasite-type CoN2 is 216(18) GPa, which is comparable to that of RhN2. This indicates that the interatomic distance of the N-N dimer in marcasite-type CoN2 is short because of weak orbital interaction between cobalt and nitrogen atoms, as in RhN2. Surprisingly, a first-principles electronic band calculation suggests that the NiAs-type FeN and CoN and marcasite-type CoN2 exhibit metallic characteristics with magnetic moments of 3.4, 0.6, and 1.2 μB, respectively. The ferromagnetic NiAs-type structure originates from the anisotropic arrangement of transition atoms stacked along the c axis.

DOI： 10.1021/acs.inorgchem.7b00516

Synthesis, crystal structure and phase transition of a Xe-N2 compound at high pressure: experimental indication of orbital interaction between xenon and nitrogen

Niwa, K; Matsuzaki, F; Hasegawa, M

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 巻 ( 1 ) 頁： 59 - 63 2017年1月

High-Pressure Synthesis and Magnetic Behavior of A-Site Columnar-Ordered Double Perovskites, LnMn(Ga0.5Ti0.5)2O6 (Ln = Sm, Gd)

Shimura, G; Niwa, K; Shirako, Y; Hasegawa, M

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 2017 巻 ( 4 ) 頁： 835 - 839 2017年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：European Journal of Inorganic Chemistry

A-site columnar-ordered double perovskites, LnMn(Ga0.5Ti0.5)2O6(Ln = Sm, Gd), were successfully synthesized under high pressure and high temperature (6 GPa, 1375 K). From the synchrotron powder X-ray diffraction patterns, all of the diffraction peaks can be indexed by the P42/nmc space group with lattice parameters a, c ≈ 2ap(ap: primitive cubic perovskite lattice) and no ordering of the B-site cations. Rietveld analysis of the synchrotron powder X-ray diffraction patterns and Curie–Weiss fitting of their magnetizations reveal that the ionic formulae of these perovskites are Ln3+Mn2+(Ga3+0.5Ti4+0.5)2O2–6. SmMn(Ga0.5Ti0.5)2O6shows canted-antiferromagnetic behavior, whereas GdMn(Ga0.5Ti0.5)2O6exhibits two different magnetic states at low temperature depending on the applied magnetic field and shows an unusual magnetization curve. These magnetic behaviors originate by decreasing the antiferromagnetic interaction by substituting Ga3+(d10) for Ti4+(d0) and by decreasing the ferromagnetic interaction between columnar-ordered Ln3+and Mn2+.

DOI： 10.1002/ejic.201601392

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CiNii Research

Microbeam hard X-ray photoelectron and ion-beam analyses of Nb hydrides formed in supercritical water

Kazuo Soda, Shinya Sugiura, Kanta Yamaguchi, Masahiko Kato, Ken Niwa, Masashi Hasegawa, Kohtaku Suzuki, Ryoya Ishigami, Eiji Ikenaga

International Symposium on Atomic Level Characterizations for New Materials and Devices ‘17 Proceedings 2017年

High pressure stability and ambient metastability of marcasite-type rhodium pernitride 査読有り

K. Niwa, T. Terabe, K. Suzuki, Y. Shirako, M. Hasegawa

Journal of Applied Physics 119 巻頁： 065901 2016年

Multicomponent A-site ordered perovskite BiMn3(Fe0.25Ti0.75)4O12: High-pressure synthesis, crystal chemistry and magnetic behavior 査読有り

G. Shimura, K. Niwa, Y. Shirako, S. Muto, K. Kusaba, M. Hasegawa

Solid State Communications 234-235 巻頁： 40-44 2016年

Molecular routes syntheses of graphite-like C-N compounds with various N/C ratios in high pressure and temperature 査読有り

T. HORIBE, K. KUSABA, K. NIWA, M. HASEGAWA, K. YASUDA, R. ISHIGAMI

Journal of the Ceramic Society of Japan 124 巻 ( 10 ) 頁： 1013-1016 2016年

High-pressure synthesis and relationship between A-site ordering and local structure of multicomponent perovskites(Ln0.25Mn0.75) (Al0.25Ti0. 75)O3, Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Y 査読有り

G. Shimura, Y. Shirako, K. Niwa, M. Hasegawa

Journal of Solid State Chemistry 242 巻頁： 55-62 2016年

Angle-resolved hard x-ray photoemission study of Nb hydride formation in high-pressure supercritical water 査読有り

Kazuo Soda, Hiroki Kondo, Kanta Yamaguchi, Masahiko Kato, Tatsuhito Shirak, Ken Niwa, Keiji Kusaba, Masashi Hasegawa, Kozina Xeniya, Eiji Ikenaga

Journal of Alloys and Compounds 643 巻頁： 195-200 2015年

Growth of rectangular hollow tube crystals with rutile-type structure in supercritical fluids 査読有り

K. Niwa, H. Ikegaya, T. Taguchi, S. Muto, T. Tokunaga and M. Hasegawa

Journal of Physics: Conference Series (JPCS) 500 巻頁： 022007 2014年

High pressure synthesis of marcasite-type rhodium pernitride 査読有り国際共著

K. Niwa, D. Dzivenko, K. Suzuki, R. Riedel, I. Troyan, M. Eremets and M. Hasegawa

Inorganic Chemistry 53 巻頁： 697-699 2014年

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