Toetsu Shishido

A novel hydrogen-evolving photocatalyst InVO4 active under visible light irradiation

Abstract InVO4, with band gap of about 2.0 eV, was found to be a new visible light responding photocatalyst for water decomposition. The photocatalyst showed activity to visible light in a wide wavelength range up to 600 nm. Although the native photocatalyst could evolve H2 from pure water under visible light irradiation (λ>420 nm ) , the photocatalytic activity increases significantly by loading NiO as a co-catalyst. Correlation of the photocatalytic properties with crystal and electronic structure of the compound is discussed in connection with the recently reported 4d and 5d transition metal photocatalysts InNbO4 and InTaO4.

MnSi and MnSi2−x single crystals growth by Ga flux method and properties

MnSi and MnSi 2- single crystals were grown from high temperature gallium metal fluxes by slowly cooling the melt in argon atmosphere. The growth conditions of MnSi and MnSi 2-x (Mn 15 Si 26 ) crystals with relatively large size, namely MnSi about 0.06 x 0.52 x 2.43 mm 3 and Mn 15 Si 26 about 0.40 × 0.55 x 0.61 mm 3 were established. MnSi crystals were generally obtained in the form of needle-like prisms extending in the direction and with well-developed (111) faces. Mn 15 Si 26 crystals had a nearly spherical polyhedral shape, greyish color and metallic luster. The as-grown MnSi and Mn 15 Si 26 crystals were used for chemical analyses and measurements of unit cell parameters. Vickers microhardness was determined on MnSi and Mn 15 Si 26 crystals, and oxidation at high temperature in air was studied for MnSi and Mn 15 Si 26 crystals.

Crystal structure of DyMnO3

Abstract A single crystal of DyMnO3 was grown by floating zone method and the crystal structure was determined by single crystal X-ray diffractometry. The structure of DyMnO3 belongs to the orthorhombic system (space group is Pnma, No. 62) with the lattice parameters a=5.842(2), b=7.378(2), c=5.280(2) A and Z=4.

Crystal growth and crystal structures of the LnMnO3 perovskites: Ln=Nd, Sm, Eu and Gd

Abstract Single crystal of LnMnO3 (Ln=Nd, Sm, Eu and Gd) was grown by floating zone method, and the crystal structure was determined by single crystal X-ray diffractometry. The structure of LnMnO3 belongs to the orthorhombic system (space group is Pnma, No. 62) with the lattice parameters a≈ 2 ap, b≈2ap, c≈ 2 ap and Z=4, where ap is ideal cubic perovskite cell parameter.

Growth of Single Crystals in the Bi-Sr-Ca-Cu-O System Using KCl as a Flux

Single crystals of Bi2Sr2CaCu2Ox having good crystallinity were successfully obtained. Nitrates of Bi, Sr, Ca and Cu were used as raw materials. Specially prepared solute calcined at low temperatures (below 500°C) were used with a KCl flux. The solvation of this solute to the KCl flux proceeded very smoothly. Single crystals having smooth surface were extracted from the KCl flux. Fundamental electrical and magnetic properties of the crystals have been investigated.

Rare earth rhodium borides with the perovskite structure

Abstract Single-crystal perovskite borides of LnRh3B (Ln ≡ Sm, Gd, Er or Yb) were prepared by the flux method. X-ray analysis revealed that the crystal structures were of the cubic perovskite type with cell dimensions of 4.193 A for SmRh3B, 4.183 A for GdRh3B, 4.147 A for ErRh3B and 4.136 A for YbRh3B. These data are in good agreement with those obtained for arc-melted polycrystalline ingots. The stability of these compounds is considered in terms of a charge transfer mechanism from the lanthanide to the Rh—B bonds to form three non-metal p orbitals or two non-metal p Orbitals and two hybrid sp orbitals. The nonstoichiometry of boron and the valence state of the rare earth elements are also discussed.

Fast and High-Energy-Resolution Oxide Scintillator: Ce-Doped (La,Gd)2Si2O7

A novel scintillation crystal (Ce0.01,Gd0.90,La0.09)2Si2O7 (Ce:La-GPS) was grown by the floating zone method, and its optical and scintillation properties were investigated. The emission wavelength of this material was 390 nm. Gamma ray excited pulse height and scintillation decay measurement showed that Ce:La-GPS had a high energy resolution (FWHM) of 5% at 662 keV, high light output of 36,000 photons/MeV and fast scintillation decay time of 46 ns.

Crystal growth by molten metal flux method and properties of manganese silicides

Abstract Crystals of binary manganese silicides were grown from high temperature copper, tin and lead metal fluxes by slow cooling method under an argon atmosphere. The growth conditions for obtaining single crystals of relatively large size were established. For tin and lead fluxes, the three silicides Mn 5 Si 3 , MnSi, and Mn 27 Si 47 crystals were prepared, and Mn 5 Si 3 (about 0.1×0.1×6.4 mm 3 ) and MnSi (about 0.9×1.0×9.2 mm 3 ) were obtained of relatively large size from the tin flux. For copper flux, only the two silicides MnSi and Mn 5 Si 3 were formed, and the crystals were somewhat smaller. As-grown Mn 5 Si 3 , MnSi, and Mn 27 Si 47 crystals were used for chemical analyses and measurements of density and unit cell parameters. The chemical analyses of the crystals are discussed. Vickers microhardness and electrical resistivity were determined on MnSi and Mn 5 Si 3 crystals, and oxidation at high temperature in air was studied for Mn 5 Si 3 , MnSi, and Mn 27 Si 47 crystals.

Compositional variation in Si-rich SiGe single crystals grown by multi-component zone melting method using Si seed and source crystals

The effect of the supply of depleted Si solute elements on the compositional variation in the Si-rich SiGe bulk crystals was studied using the method which was used to grow Ge-rich SiGe single crystals with a uniform composition. By selecting the proper pulling rate, we can obtain Si-rich Si1−xGex bulk crystals with uniform composition of x=0.1 without using the supply mechanism of depleted Si solute elements. When the supply mechanism of Si solute elements was used, the initial composition in Si-rich SiGe crystals can be much more easily determined by controlling the growth temperature than that in Ge-rich crystals because the Si seed crystal is not melted down. The supply of Si solute elements is very effective to change the compositional variation even for Si-rich SiGe crystals.

Synthesis and characterization of the nonstoichiometric perovskite-type compound ScRh3Bx

Abstract Polycrystalline samples of ScRh 3 B x (0≤ x ≤1.0) were synthesized by the arc melting method. The crystal structure is the perovskite-type cubic structure (space group Pm3m ) for boron content in the range 0≤ x ≤1.0 (0–20 at.% B). The lattice parameter a varies linearly from a =0.3903(1) nm ( x =0) to 0.40799(3) nm ( x =1.0). The micro-Vickers hardness increases with increasing boron content from 1.9 (±0.1) GPa for ScRh 3 (0 at.% B) to 9.9 (±0.1) GPa for ScRh 3 B 1.0 (20 at.% B). Thermogravimetric analysis indicates that the oxidation onset temperature for stoichiometric ScRh 3 B is 868 K. A sharp exothermic peak is observed at 1068 K by differential thermal analysis. The weight gain of the sample by heating in air up to 1473 K is 12.7%. The weight gain increases with increasing boron content. All samples in the range 0≤ x ≤1.0 show a metallic temperature dependence of the resistivity down to 0.5 K. Magnetic susceptibilities also show Pauli paramagnetic behavior and no trace of magnetic transitions on superconductivity in any of the samples.