A5015219829- Advanced Thermoelectric Materials and Devices
- High Entropy Alloys Studies
- Ferroelectric and Piezoelectric Materials
- Hydrogen Storage and Materials
- Acoustic Wave Resonator Technologies
- X-ray Diffraction in Crystallography
- Advanced Condensed Matter Physics
- Iron-based superconductors research
- Crystallization and Solubility Studies
- Thermal Expansion and Ionic Conductivity
- High-pressure geophysics and materials
- Magnetic and transport properties of perovskites and related materials
- Optical properties and cooling technologies in crystalline materials
- Chalcogenide Semiconductor Thin Films
- Rare-earth and actinide compounds
- Microwave Dielectric Ceramics Synthesis
- Inorganic Chemistry and Materials
- Physics of Superconductivity and Magnetism
- Ammonia Synthesis and Nitrogen Reduction
- Intermetallics and Advanced Alloy Properties
- Multiferroics and related materials
- Advanced Thermodynamics and Statistical Mechanics
- Luminescence Properties of Advanced Materials
- Metal and Thin Film Mechanics
- Boron and Carbon Nanomaterials Research
National Institutes for Quantum Science and Technology
2022-2025
Tokyo Metropolitan University
2021-2023
Hiroshima University
2016-2021
Nagoya City University
2018-2019
Hydrogen can be stored in the interstitial sites of lattices intermetallic compounds. To date, compound LaNi5 or related LaNi5-based alloys are known to practical hydrogen storage materials owing their higher volumetric densities, making them a compact method and allowing stable reversible absorption desorption reactions take place at room temperature below 1.0 MPa. By contrast, gravimetric density is required for key improvements (e.g., LaNi5: 1.38 mass%). Although have typically been...
Abstract A large piezoelectric response in ferroelectric ceramics is typically associated with extrinsic contributions from domain structures. However, such structures cannot be expected systems pseudo-cubic symmetry. In this study, we determine the mechanism of significant piezoelectricity and ferroelectricity 0.3BaTiO 3 –0.1Bi(Mg 1/2 Ti )O –0.6BiFeO ceramic a perovskite-type Synchrotron radiation X-ray diffraction reveals that Bi ions essentially prefer to off-centered at six sites by...
Contributions to the piezoelectric response in pseudocubic 0.3BaTiO3-0.1Bi(Mg1/2Ti1/2)O3-0.6BiFeO3 ceramics were investigated by synchrotron X-ray diffraction under electric fields. All of lattice strain determined from 110, 111, and 200 peaks showed similar hysteresis that was comparable bulk butterfly-like curve. It suggested lack anisotropy related complex domain structure phase boundary composition.
High-entropy-alloy (HEA) superconductors are a new class of disordered superconductors. However, commonality superconducting characteristics HEA materials is unclear. Here, we have investigated the crystal and electronic structure, robustness states in HEA-type metal telluride (MTe; M = Ag, In, Sn, Pb, Bi) under high pressure, results were compared with pressure effects for middle-entropy system (AgPbBiTe3) reference PbTe. When structure CsCl-type, all phases show superconductivity but...
Recently, robustness of superconductivity to external pressure has been observed in high-entropy (HE) metal telluride (MTe). Here, we investigated the atomic displacement parameters (Uiso), vibration characteristics, and electronic structure MTe with various configurational entropies mixing (ΔSmix) at M site understand origin superconductivity. Uiso clearly increased by M-site alloying ΔSmix ≥ 1.1R, which is evidence created local disorder NaCl-type (low-pressure) phases. The simulated...
Hydrogen storage materials store hydrogen in their atomic states, enabling more compact and safer methods compared to those for gaseous liquid hydrogen. Although various types of have been reported, new with higher capacities enhanced durability are required. Herein, we report the synthesis, crystal structure, properties an AB3-based alloy, Y0.68Mg0.32Co3.00, which exhibited reversible absorption desorption a capacity 1.68 mass % minimal degradation over 100 cycles at 303 K. The...
The hydrogen sorption properties of single-phase bcc (TiVNb)100–xCrx alloys (x = 0–35) are reported. All absorb quickly at 25 °C, forming fcc hydrides with storage capacity depending on the Cr content. A thermodynamic destabilization hydride is observed increasing concentration, which agrees well previous compositional machine learning models for metal thermodynamics. steric effect or repulsive interactions between Cr–H might be responsible this behavior. cycling performances TiVNbCr alloy...
Abstract Metastable solid electrolytes exhibit superior conductivity compared to stable ones, making them a subject of considerable interest. However, synthesis the metastable phase is affected by multiple thermodynamic and kinetic parameters, leading ambiguity in organization stability metastability. In this study, we organized remnant intermediate metastability based on temperature. The phase, which less than temperature-independent typically transforms into phase(s) at high temperatures....
Reconstructing the surface nature of metal-organic frameworks (MOFs) as precatalytic structures is a promising methodology for improving electrocatalytic performance. However, regulating structural evolution MOFs during electrolysis remains highly uncontrollable and lacks an in-depth understanding role
The thermal stability of an equilibrium phase may be tuned due to lattice strain and distortion induced by nanosizing. We apply these effects destabilize magnesium hydride, a promising hydrogen storage material owing its high gravimetric density but with too operating temperature/low supply pressure for most practical applications. destabilization is attempted MgH2 in contact entropy alloy (HEA), which multiple metal atoms lead distortion. Here, two HEAs, CrMnFeCoNi face centered cubic (fcc)...
We investigated the structural phase transition of ${\mathrm{BaAl}}_{2}{\mathrm{O}}_{4}$, which has a network structure with corner-sharing ${\mathrm{AlO}}_{4}$ tetrahedra, via synchrotron x-ray thermal diffuse scattering measurements and first-principles calculations. ${\mathrm{BaAl}}_{2}{\mathrm{O}}_{4}$ shows at ${T}_{\mathrm{C}}=451.4$ K from $P{6}_{3}22$ parent crystal to low-temperature superstructure cell volume...
Crystallography and dielectric properties in Dion-Jacobson layered perovskites, CsNdNb$_2$O$_7$ RbNdNb$_2$O$_7$, have been examined dense polycrystalline samples, polarization hysteresis loops that substantiate ferroelectricity observed at room temperature. The theoretical mechanism for the spontaneous polarization, "hybrid improper ferroelectric mechanism,'' induced by a combination of two types non-polar octahedral rotations, is confirmed these phases. Our samples show remanent...
We investigated the correlation between crystal structures and spin states of cobalt perovskites ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Pr}}_{x}{\mathrm{CoO}}_{3}$ $(x=0.30, 0.34)$ by x-ray powder diffraction, transmission electron microscopy, magnetic measurements at low temperatures. The $x=0.30$ $x=0.34$ compounds exhibit structural phase transitions a low-temperature orthorhombic (Pbnm) high-temperature rhombohedral $(R\overline{3}c)$ around 170 250 K, respectively. In fairly wide...
Changes in crystal structures of lead-free BaTiO3 (BT) and lead-based 0.70Pb(Mg1/3Nb2/3)–0.30PbTiO3 (PMN–PT) single crystals with a perovskite-type structure have been investigated under applied electric field by analyzing the high-energy synchrotron radiation X-ray diffraction data. The experiment is performed within cubic phase diagram range temperatures fields where no field-induced transition caused. analysis demonstrates that system change to tetragonal electrostriction when along axis....
Structural phase transitions of calcium strontium sulfoaluminate series, (Ca1-xSrx)8[AlO2]12(SO4)2 ((CS)AS-x) with x = 0.80-1.00, are systematically investigated by powder X-ray diffraction, dielectric measurements, and pyroelectric to clarify a diagram (CS)AS-x (x 0.80-1.00). A pure sulfoaluminate, (CS)AS-1.00, is found undergo three transitions, which take place successively on cooling from prototypical cubic the symmetry Im3̅m. Though room-temperature (CS)AS-1.00 was previously reported...
Zintl arsenide Eu 5 In 2 As 6 is demonstrated as a bipolar dopable thermoelectric material.
We estimated Grüneisen parameter (γG) to investigate lattice anharmonicity in a layered BiS2-based superconductor system REO1−xFxBiS2 (RE = La, Ce, Pr, Nd), where in-plane chemical pressure was tuned by the ionic radii of RE elements, and carrier concentration F concentration. With increasing pressure, bulk modulus remarkably increases, larger γG is observed for Nd. The dependence on exhibits good correlation with Tc, suggesting that results higher Tc system. In addition, shows slight...
Rare-earth substitution effects on atomic motions in resonantly vibrating piezoelectric oscillators of langasite-type crystals, namely, La3Ga5SiO14 (LGS) and Nd3Ga5SiO14 (NGS), are revealed by time-resolved X-ray crystal structure analysis under alternating electric fields. Deformations Ga–O–Ga Ga–O–Ga/Si bond angles accompanying deformations RE–O (RE: La or Nd) lengths found LGS suppressed NGS. Alternatively, rigid GaO6 octahedra deformed The decreases caused the Nd would make more...
To investigate the structural fluctuations of relaxor Pb(Mg1/3Nb2/3)O3 (PMN) in cubic phase, probability density function each atom was determined by high-energy synchrotron radiation X-ray powder diffraction measurements and a Rietveld analysis with anharmonic temperature factors. A rotator-like behavior Pb ion observed phase. The off-center along 〈1 1 1〉 directions became pronounced decreasing temperature. ferroelectricity PMN attributed to combination freezing 1〉-preferred disorder...
We report results of the time-resolved x-ray structure analysis a relaxor ferroelectric single crystal under an alternating electric field. The time dependence lattice strain, atomic displacements, and domain volumes in $0.955\mathrm{Pb}(\mathrm{Z}{\mathrm{n}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}){\mathrm{O}}_{3}\ensuremath{-}0.045\mathrm{PbTi}{\mathrm{O}}_{3}$ (PZN-4.5PT) during piezoelectric straining switching is revealed. strain induced by field consistent with that expected from constants....
We report the successful synthesis, crystal structure, and electrical properties of Sr3Re2O9, which contains Re6+ with 5d1 configuration. This compound is isostructural Ba3Re2O9 shows a first-order structural phase transition at ∼370 K. The low-temperature (LT) crystallizes in hettotype structure Ba3Re2O9, different from that LT Sr3W2O9, suggesting electronic state plays an important role determining phase. accompanied by sharp change resistivity. likely metal–insulator transition, as...
As thermoelectric generators can convert waste heat into electricity, they play an important role in energy harvesting. The metal chalcogenide AgBiSe2 is one of the high-performance materials with low lattice thermal conductivity (klat), but it exhibits temperature-dependent crystal structural transitions from hexagonal to rhombohedral, and finally a cubic phase as temperature rises. high figure-of-merit ZT obtained only for high-temperature phase. In this study, we utilized...