Masanobu Saeki

Crystal structures of V3S4 and V5S8

Abstract Crystal structures of the ordered phases of V3S4 and V5S8 were refined with single crystal data. Both are monoclinic. Chemical compositions, space groups and lattice constants are as follows: VS1.47, I2 m (No. 12), a = 5.831(1), b = 3.267(1), c = 11.317(2)A, β = 91.78(1)° and VS1.64, F 2 m (No. 12), a = 11.396(11), b = 6.645(7), c = 11.293(4), A, β = 91.45(6)°. In both structures, short metal-metal bonds were found between the layers as well as within them. In comparison with the structure of Fe7S8, the stability of NiAs-type structure was discussed based on the detailed metal-sulfur distances.

Chemical transport of non-stoichiometric TiS2

Abstract The mechanism of the chemical transport reaction for the preparation of non-stoichiometric TiS2 crystals has been studied through quartz Bourdon gauge measurements and through UV and VIS spectroscopy. Crystals of the TiS2 phase were transported with iodine from higher to lower temperature. The grown crystals were riched in sulfur than the starting material. The results have been interpreted quantitatively on the basis of the equilibrium sulfur pressure of the TiS2 phase.

Crystal growth of V6O13

Abstract V 6 O 13 single crystals were prepared by chemical transport method. From the electrical measurements of these crystals, a semiconductor/semiconductor transition was found. Based on the crystallographic and electrical measurements, we suggest that the transition is of the first order.

Preparation and Physical Properties of PrBa2Cu3Oy

A new compound, PrBa2Cu3Oy, which is isomorphic with YBa2Cu3Oy, was prepared as single phase. With specimens quenched from 920°C, the oxygen content y was 6.8 ± 0.1 and the ratio of Pr3+ to Pr4+ was 0.4:0.6. With furnace-cooled specimens, the value of y was 7.1 ± 0.1 and the ratio became 0.1:0.9. The average valence of Cu ions was 2.0 ± 0.1 for the former and 2.1 ± 0.1 for the latter. Specimens handled both ways were nonmetallic and nonsuperconducting down to 4.2 K.

Structure refinement of the incommensurate composite crystal Sr1.145TiS3 through the Rietveld analysis process

The structure of the incommensurate composite crystal of the trigonal sulfide Sr 1.145 TiS 3 , M r =244.42, has been analyzed on the basis of the four-dimensional superspace group P R3m 1s using powder X-ray diffraction data and the Rietveld analysis process. The unit cell and other crystal data are a 1 =a 2 =11.5108 (2), a 3 =2.99094 (5) A, a=[000.57227 (2)], V=343.19 A 3 , D x =3.548 Mg m -3 and Z=3. R wp was 0.104 on an incommensurate modulated structure model with 47 structural parameters. The crystal is composed of columns of face-shared polyhedra, (TiS 6/2 )∞, and rows of Sr, and both are parallel to the c axis

Powder X-ray diffraction data and crystal structures of ternary sulphides, Ba2TiS4, Ba3TiS5 and tetragonal BaCu2S2

The structures of Ba2TiS4 [orthorhombic, Pnma, a=9.056A, b=6.854A, c=12.304A], Ba3TiS5 [tetragonal, I4/mcm, a=8.465A, c=13.767A] and new-type of BaCu2S2 [tetragonal, I4/mmm, a=3.909A, c=12.648A] were refined on the basis of the powder X-ray diffraction data. Ba2TiS4, Ba3TiS5 and tetragonal BaCu2S2 were confirmed to be isostructural with β-K2SO4, Cs3CoCl5 and ThCr2Si2 respectively.

Preparation of a new type BaCu2S2

Abstract A new type of BaCu 2 S 2 has been prepared through the sulphurization of a mixture of BaCO 3 and CuO. The X-ray powder diffraction pattern of the sulphide was indexed on the basis of tetragonal cell with the lattice parameters of a = 3.909(6) and c = 12.655(2)A.

Crystal growth of nonstoichiometric V5S8 by chemical transport

Abstract The relation between the composition of the starting material and the product crystal has been studied during the preparation of single crystals of nonstoichiometric compounds by closed system chemical transport. Sulphides of the V 5 S 8 - and V 3 S 4 - phases were examined. Because of the high equilibrium sulphur partial pressure of these compounds, the sulphur pressure was uniform in the tube and was determined by the equilibrium sulphur partial pressure of the starting material in the high-temperature region. This caused the deposition of sulphur-rich crystals in the low-temperature region.

Crystal growth of vanadium dioxide

Abstract The phase diagram of the V-O system at 1500°K has been re-examined (mainly in the VO2 region) and vanadium dioxide crystals have been grown from vanadium pentoxide (M.P. about 950°K) under various oxygen partial pressures. The total pressure was one atm. The chemical analyses of these oxides indicated the stability range of VO2+x from x=0.00 to x=0.07 with corresponding oxygen partial pressures from 10−4.1 to 10−2.9 atm. Electrical resistance measurements on these crystals document the phase changes.

Preparation and crystal structures of new barium zirconium sulfides, Ba2ZrS4 and Ba3Zr2S7

Abstract New barium zirconium sulfides, Ba 2 ZrS 4 and Ba 3 Zr 2 S 7 , have been prepared by the reaction of CS 2 with mixture of BaCO 3 and BaZrO 3 . The crystal structures of the compounds were refined on the powder X-ray diffraction data. The result showed that Ba 2 ZrS 4 [tetragonal, I 4/ mmm , a = 4.7852(1) A and c = 15.9641(3) A] crystallizes in the K 2 NiF 4 type structure, and Ba 3 Zr 2 S 7 [orthorhombic, Cccm , a = 7.0697(2) A, b = 25.4923(7) A and c = 7.0269(2) A] has a distorted variant of the X 3 Y 2 Z 7 type structure which is closely related to the perovskite structure.