Research Center for Materials Nanoarchitechtonics
National Institute for Materials Science
Inorganic solid state chemistry, high-pressure synthesis, low-temperature sysnthesis, flux crystal growth, ionic conductors, nonlinear optics, low-dimensional magnetism
Robert D. Smyth, Dmitry Khalyavin, Yoshihiro Tsujimoto, Kazunari Yamaura, and Simon J. Clarke Elsevier BV
Louis-Béni Mvélé, Shunsuke Sasaki, Philippe Deniard, Yoshihiro Tsujimoto, Etienne Janod, Catherine Guillot-Deudon, Maria Teresa Caldes, Isabelle Braems, Benoit Corraze, Stéphane Jobic,et al. American Chemical Society (ACS)
Kouta Kazama, Masato Sakano, Kohei Yamagami, Takuo Ohkochi, Kyoko Ishizaka, Terumasa Tadano, Yusuke Kozuka, Hidetoshi Yoshizawa, Yoshihiro Tsujimoto, Kazunari Yamaura,et al. American Physical Society (APS)
Hong Yan, Kotaro Fujii, Houria Kabbour, Akira Chikamatsu, Yu Meng, Yoshitaka Matsushita, Masatomo Yashima, Kazunari Yamaura, and Yoshihiro Tsujimoto American Chemical Society (ACS)
Band gap engineering using multiple anions is an established approach to novel photocatalysts that exhibit suitable band gap energies for water splitting and high photocorrosion resistance. However, few studies have been conducted on photocatalysts with polyanions, including polychalcogenide ions. Here, we present a new quaternary gallium oxysulfide with disulfide pairs (S2)2-, La4Ga2S8O3, grown out of a KI molten salt. Single-crystal X-ray diffraction analysis revealed that the oxysulfide crystallizes in the orthorhombic space group Pbcn with lattice constants of a = 18.3330(6) Å, b = 13.0590(5) Å, and c = 5.9022(3) Å. In the crystal structure, the GaS4-based zigzag chains and OLa4-based fluorite-like strips are independently arranged in two dimensions, which alternately stack via the disulfide pairs along the third direction. The oxysulfide is a direct-type semiconductor with a band gap of 2.45 eV. First-principles calculations combined with X-ray photoemission spectroscopy measurements show that S 3p states derived from the disulfide pairs dominate the valence band maximum and conduction band minimum, and these band-edge positions are suitable for the oxidation and reduction of water. Our comprehensive study based on the electronic structure suggests that the disulfide pairs make La4Ga2S8O3 a potential photocatalyst for water splitting under visible-light irradiation.
Xun Kang, Ryuta Ishikawa, Alexei A. Belik, Yoshihiro Tsujimoto, Satoshi Kawata, and Kazunari Yamaura American Chemical Society (ACS)
Xun Kang, Alexei A. Belik, Yoshihiro Tsujimoto, and Kazunari Yamaura American Chemical Society (ACS)
Under high-pressure and high-temperature conditions, doped Bi3Re3O11 and Bi3Os3O11 with Fe up to 29 atomic % were synthesized. The crystal structures and chemical compositions of Bi3Os2.45Fe0.55O11 and Bi3Re2.13Fe0.87O11 were determined by synchrotron powder X-ray diffraction and electron probe microanalysis. Both crystal structures were explained by a KSbO3-type model with the space group Pn3̅. Magnetic and electronic transport property measurements showed that Bi3Os2.45Fe0.55O11 exhibited a ferrimagnetic transition at the highest magnetic ordering temperature of 490 K in the KSbO3-type, while Bi3Re2.13Fe0.87O11 exhibited a spin glassy behavior below 22 K. The magnetoresistance at 5 K and 90 kOe was almost zero for Bi3Os2.45Fe0.55O11, but -10% for Bi3Re2.13Fe0.87O11. These results suggest that KSbO3- type 5d oxides, which exhibit only weak temperature-dependent paramagnetism to date, are a group of compounds that can be converted into spintronic materials by doping with 3d elements, leading to the development of new KSbO3-type materials with both theoretical and practical significance.
Jie Chen, Yoshihiro Tsujimoto, Alexei A. Belik, Kazunari Yamaura, and Yoshitaka Matsushita International Union of Crystallography (IUCr)
The crystal structure of the cubic double-perovskite Sr2Cr0.84Ni0.09Os1.07O6, grown at high pressure, was solved using intensity data measured at 113 K. The Os site was modelled with a partial Ni occupancy, and the Cr site was modelled with both Os and Ni partial occupancy. The refined structure shows that this cubic form is stable at 113 K.
Yoshihiro Tsujimoto, Jun Sugiyama, Masayuki Ochi, Kazuhiko Kuroki, Pascal Manuel, Dmitry D. Khalyavin, Izumi Umegaki, Martin Månsson, Daniel Andreica, Shigeo Hara,et al. American Physical Society (APS)
Yu Su, Yuki Iwasa, Takayuki Yanagida, Yoshihiro Tsujimoto, Shunqin Luo, and Hiraku Ogino Optica Publishing Group
Herein, we report the synthesis and luminescence properties of Tb-doped layered perovskite oxychloride, Ba3Y2O5Cl2. Similar to Ba3Y2O5Cl2:Eu3+, single-phase Ba3Y2O5Cl2:Tb3+ was successfully synthesized through a solid-state reaction. The luminescence properties were studied and compared with those of Y2O3:Tb3+. There was only one excitation peak due to the 4f-5d transition of Tb3+, which was different from that of Y2O3:Tb3+ that comprises two peaks. Green emissions from Tb3+ 4f−4f transitions were observed for both the samples. The luminescence properties at different doping concentrations were investigated. Concentration quenching at 8% was found, which is rather high, owing to the specially separated layered structure. The decay times of luminescence were also studied, which are consistent with the concentration quenching. In addition, energy diagram for the luminescence mechanism were also proposed. Considering the photoluminescence spectra and high concentration quenching, this compound is a potential mother compound for optical materials, especially for the green phosphors.
Biswajit Dalal, Xun Kang, Yoshitaka Matsushita, Alexei A. Belik, Yoshihiro Tsujimoto, and Kazunari Yamaura American Physical Society (APS)
Yanchang Wang, Kentaro Yamamoto, Yoshihiro Tsujimoto, Toshiyuki Matsunaga, Datong Zhang, Zulai Cao, Koji Nakanishi, Tomoki Uchiyama, Toshiki Watanabe, Tsuyoshi Takami,et al. American Chemical Society (ACS)
Hiroshi Yaguchi, Kotaro Fujii, Yoshinori Tsuchiya, Hiraku Ogino, Yoshihiro Tsujimoto, and Masatomo Yashima American Chemical Society (ACS)
Hong Yan, Yoshitaka Matsushita, Kazunari Yamaura, and Yoshihiro Tsujimoto Wiley
Chalcogenide-containing compounds have been widely studied as infrared nonlinear optical (NLO) materials. However, they have never been applied in the ultraviolet (UV) region owing to the high energy levels of chalcogen anions, leading to band gap narrowing. In this paper, we report the synthesis of a new UV NLO oxysulfide La 3 Ga 3 Ge 2 S 3 O 10 with an exceptionally wide band gap of 4.70 eV due to from the unique anion-ordered frameworks comprising 1D 1 ¥ [(Ga 3/5 Ge 2/5 ) 3 S 3 O 3 ] triangular tubes and 0D (Ga 3/5 Ge 2/5 ) 2 O 7 dimers of corner-sharing (Ga/Ge)S 2 O 2 and (Ga/Ge)O 4 tetrahedra, respectively. Second harmonic generation (SHG) measurements revealed that La 3 Ga 3 Ge 2 S 3 O 10 was phase matchable with twice the SHG response of KH 2 PO 4 . The results of theoretical calculations suggest that the strong SHG response is mainly attributable to the S-3 p and O-2 p orbitals in the occupied states. The anion-directed band-gap engineering may give insights into the application of NLO oxychalcogenides in the UV regions.
Hai L. Feng, Chang-Jong Kang, Pascal Manuel, Fabio Orlandi, Yu Su, Jie Chen, Yoshihiro Tsujimoto, Joke Hadermann, Gabriel Kotliar, Kazunari Yamaura,et al. American Chemical Society (ACS)
Hong Yan, Yoshitaka Matsushita, Akira Chikamatsu, Tetsuya Hasegawa, Kazunari Yamaura, and Yoshihiro Tsujimoto American Chemical Society (ACS)
A new ternary chromium disulfide, Ba9Cr4S19, has been grown out of BaCl2 molten salt. Single-crystal structure analysis revealed that it crystallizes in the centrosymmetric space group C2/c with lattice parameters: a = 12.795(3) Å, b = 11.3269(2) Å, c = 23.2057(6) Å, β = 104.041(3)°, and Z = 4. Ba9Cr4S19 comprises four face-sharing Cr-centered octahedra with disulfide ions occupying sites on each terminal face. The resulting Cr4S15 tetramer units are isolated by nonmagnetic Ba-centered polyhedra in the ab plane and barium disulfide (=Ba4(S2)2) layers along the c-axis. Following the structure analysis, the title compound should be expressed as [Ba2+]9[Cr3+]4[(S2)2–]4[S2–]11, which is also consistent with Cr2p X-ray photoemission spectra showing trivalent states of the Cr atoms. The unique Cr-based zero-dimensional structure with the formation of these disulfide ions can be achieved for the first time in ternary chromium sulfides, which adopt 1–3 dimensional frameworks of Cr-centered polyhedra.
Yuki Iwasa, Yu Su, Yoshinori Tsuchiya, Makoto Tatsuda, Kohji Kishio, Takayuki Yanagida, Fumi Takada, Taichiro Nishio, Yoshihiro Tsujimoto, Kotaro Fujii,et al. Royal Society of Chemistry (RSC)
We report the synthesis, crystal structure, and optical properties of a new layered perovskite oxychloride, Ba3Y2O5Cl2.
Henrik Jacobsen, Hai L. Feng, Andrew J. Princep, Marein C. Rahn, Yanfeng Guo, Jie Chen, Yoshitaka Matsushita, Yoshihiro Tsujimoto, Masahiro Nagao, Dmitry Khalyavin,et al. American Physical Society (APS)
We report on the structural, magnetic, and electronic properties of two new double-perovskites synthesized under high pressure; Pb2CaOsO6 and Pb2ZnOsO6. Upon cooling below 80 K, Pb2CaOsO6 simultaneously undergoes a metal--insulator transition and develops antiferromagnetic order. Pb2ZnOsO6, on the other hand, remains a paramagnetic metal down to 2 K. The key difference between the two compounds lies in their crystal structure. The Os atoms in Pb2ZnOsO6 are arranged on an approximately face-centred cubic lattice with strong antiferromagnetic nearest-neighbor exchange couplings. The geometrical frustration inherent to this lattice prevents magnetic order from forming down to the lowest temperatures. In contrast, the unit cell of Pb2CaOsO6 is heavily distorted up to at least 500 K, including antiferroelectric-like displacements of the Pb and O atoms despite metallic conductivity above 80 K. This distortion relieves the magnetic frustration, facilitating magnetic order which in turn drives the metal--insulator transition. Our results suggest that the phase transition in Pb2CaOsO6 is spin-driven, and could be a rare example of a Slater transition.
Jie Chen, Xiao Wang, Zhiwei Hu, Liu Hao Tjeng, Stefano Agrestini, Manuel Valvidares, Kai Chen, Lucie Nataf, Francois Baudelet, Masahiro Nagao,et al. American Physical Society (APS)
Hong Yan, Akihide Kuwabara, Mark D. Smith, Kazunari Yamaura, Yoshihiro Tsujimoto, and Hans-Conrad zur Loye American Chemical Society (ACS)
Single crystals of a new germanium oxysulfide La4(GeS2O2)3 were grown out of a BaCl2-CaCl2 eutectic flux, and the crystal structure was determined via single-crystal X-ray diffraction. Ivory-white ...
Jie Chen, Hai L. Feng, Yoshitaka Matsushita, Alexei A. Belik, Yoshihiro Tsujimoto, Masahiko Tanaka, Duck Young Chung, and Kazunari Yamaura American Chemical Society (ACS)
Polycrystalline Sr3OsO6, which is an ordered double-perovskite insulator, is synthesized via solid-state reaction under high-temperature and high-pressure conditions of 1200 °C and 6 GPa. The synthesis enables us to conduct a comparative study of the bulk form of Sr3OsO6 toward revealing the driving mechanism of 1000 K ferromagnetism, which has recently been discovered for epitaxially grown Sr3OsO6 films. Unlike the film, the bulk is dominated by antiferromagnetism rather than ferromagnetism. Therefore, robust ferromagnetic order appears only when Sr3OsO6 is under the influence of interfaces. A specific heat capacity of 39.6(9) × 10-3 J mol-1 K-2 is found at low temperatures (<17 K). This value is remarkably high, suggesting the presence of possible Fermionic-like excitations at the magnetic ground state. Although the bulk and film forms of Sr3OsO6 share the same lattice basis and electrically insulating state, the magnetism is entirely different between them.
Akira Chikamatsu, Takahiro Maruyama, Tsukasa Katayama, Yu Su, Yoshihiro Tsujimoto, Kazunari Yamaura, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira, and Tetsuya Hasegawa American Physical Society (APS)
Jie Chen, Hong Yan, Akihide Kuwabara, Mark D. Smith, Yuki Iwasa, Hiraku Ogino, Yoshitaka Matsushita, Yoshihiro Tsujimoto, Kazunari Yamaura, and Hans-Conrad zur Loye Frontiers Media SA
A new germanate garnet compound, Ce2CaMg2Ge3O12, was synthesized via flux crystal growth. Truncated spherical, reddish-orange single crystals with a typical size of 0.1–0.3 mm were grown out of a BaCl2-CaCl2 melt. The single crystals were characterized by single-crystal X-ray diffraction analysis, which revealed that it adopted a cubic garnet-type structure with a = 12.5487(3) Å in the space group Ia−3d. Its composition is best described as A3B2C3O12, where Ce/Ca, Mg, and Ge occupied the A, B, and C sites, respectively. A UV–vis absorption spectroscopy measurement on the germanate garnet revealed a clear absorption edge corresponding to a band gap of 2.21 eV (λ = 561 nm). First-principle calculations indicated that the valence band maximum was composed of Ce 4f bands, whereas the conduction band minimum mainly consisted of Ce 5d bands. These findings explain the observed absorption edge through the Ce 4f → 5d absorption. Photoluminescence emission spectra exhibited a very broad peak centered at 600 nm, corresponding to transition from the lowest energy d level to the 4f levels.
Christian A. Juillerat, Yoshihiro Tsujimoto, Akira Chikamatsu, Yuji Masubuchi, Tetsuya Hasegawa, and Kazunari Yamaura Royal Society of Chemistry (RSC)
CaCrO3 synthesized by high pressure methods is topochemically treated with polyvinylidene difluoride and undergoes stepwise reduction followed by fluorine incorporation.
Takamasa Ishigaki, Yusuke Nakada, Naoki Tarutani, Tetsuo Uchikoshi, Yoshihiro Tsujimoto, Masaaki Isobe, Hironori Ogata, Chenning Zhang, and Dong Hao The Royal Society
Nano-size EVONIK AEROXIDE ® P25 titanium dioxide, TiO 2 , powder was heat-treated at temperatures, 700–900°C, in air. An X-ray diffraction study showed that the P25 powder is composed of approximately 20 and approximately 80 mass% of rutile and anatase phases, respectively. It was also shown that the transformation from anatase to rutile induced by high-temperature heat treatment was almost completed at 750°C, whereas a small amount (less than 3 mass%) of anatase phase was still left even in the powder heat-treated at 900°C. The transformation behaviour was consistent with results obtained by Raman scattering spectroscopy. Raman experiments also indicated that high-temperature heating induced the formation of oxide ion vacancies. Powders were dispersed in methyl orange (MO) aqueous solution, and the bleach rate of MO was measured to evaluate photocatalytic activity under ultraviolet (UV)- and visible-light irradiation. After the heat treatment, the UV-light photocatalytic performance sharply deteriorated. Interestingly, visible-light photocatalytic activity was enhanced by high-temperature heating and reached the highest performance for an 800°C-heated sample, indicating that the P25 powder obtained high visible-light photocatalytic performance after heat treatment. Even after 900°C heat treatment, the photocatalytic performance was higher than that of as-received powder. Enhancement of photocatalytic activities was discussed in relation to visible light absorption and charge carrier transfer.
Hai L. Feng, Madhav Prasad Ghimire, Zhiwei Hu, Sheng-Chieh Liao, Stefano Agrestini, Jie Chen, Yahua Yuan, Yoshitaka Matsushita, Yoshihiro Tsujimoto, Yoshio Katsuya,et al. American Physical Society (APS)
Room-temperature ferrimagnetism was discovered for the anti-site-disordered perovskite Ca2MnOsO6 with Tc = 305 K. Ca2MnOsO6 crystallizes into an orthorhombic structure with a space group of Pnma, in which Mn and Os share the oxygen-coordinated-octahedral site at an equal ratio without a noticeable ordered arrangement. The material is electrically semiconducting with variable-range-hopping behavior. X-ray absorption spectroscopy confirmed the trivalent state of the Mn and the pentavalent state of the Os. X-ray magnetic circular dichroism spectroscopy reveals that the Mn and Os magnetic moments are aligned antiferromagnetically, thereby classifying the material as a ferrimagnet which is in accordance with band structure calculations. It is intriguing that the magnetic signal of the Os is very weak, and that the observed total magnetic moment is primarily due to the Mn. The Tc = 305 K is the second highest in the material category of so-called disordered ferromagnets such as CaRu1-xMnxO3, SrRu1-xCrxO3, and CaIr1-xMnxO3, and hence, may support the development of spintronic oxides with relaxed requirements concerning the anti-site disorder of the magnetic ions.