Kazutoshi Ukei

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.

Structure of the incommensurate composite crystal [Ba]x[(Pt,Cu)O3]

The nonstoichiometric compound [Ba] x [(Pt,Cu)O 3 ] (x=1.317) has a composite crystal structure with R P31c 111: P 1s R3m , a=5.817 (2), c=4.233 (1) A, k=(a * +b * )/3+1.519 (1)c * , V=124.0 A 3 , Z 1 =2, Z 2 =3, D x =7.46 Mg m -3 , Mo Kα, Cu Kβ, μ(Mo Kα)=42.9 mm -1 . The structure was analyzed by a newly developed computer program based on the theory reported in a previous paper [Yamamoto (1992). Acta Cryst. A48, 476-483]. Final R factors: 0.075 (overall), 0.041 (main), 0.108 (first-order satellite), 0.102 (second-order satellite) and 0.224 (third order satellite)

Crystal growth of a new orthorhombic ErBa(Cu,Pt)O4 material: Crystal chemistry and characterization

Abstract A new compound in the quaternary oxide system, Er-Ba-Cu-Pt-O, was discovered. Single crystals were grown using CuO as a flux in a platinum crucible by a slow cooling method. The platinum was supplied from the inner wall of the platinum crucible. Chemical analysis revealed the chemical composition of this compound to be ErBa 1.03 Cu 0.77 Pt 0.46 O 4.34 . The crystal system was found to be orthorhombic (space group Pcmn) with average unit cell dimensions a = 10.287(3) A, b = 5.659(1) A and c = 13.157 (3) A. We propose the chemical formula of this compound as ErBa(Cu,Pt)O 4 . A large, but broad diamagnetic transition, which should come from the superconducting state, was observed below 80–90 K in single crystal aggregates.

Structure of the incommensurate composite crystal [Sr2Cu2O3][CuO2]x (x=1.436)

[Sr 2 Cu 2 O 3 ][CuO 2 ] x (x=1.436), M r =487.5, orthorhombic, M A21 1 m s a 1 .M A21 1 m s a 1 , a=11.457 (5), b=13.409(9), c 1 =3.395 (3), c 2 =2.740 (2) A, k 1 =b * + 1.436 (2)c 1 * , k 2 =b * +0.696 (1)c 2 * , V 1 =604.5, V 2 = 420.9 A 3 , Z=4, D x =5.36 Mg m -3 , Mo Kα, λ= 0.71073 A, μ=28.5 mm -1 , F(000)=890.5, room temperature, final R=0.057 for 314 unique reflections. The first subsystem [Sr 2 Cu 2 O 3 ] is composed of (Cu 2 O 3 )∞ shetts perpendicular to the b axis and Sr ions coordinated to the sheet. The second subsystem is (CuO 2 )∞ infinite chains parallel to the c axis, which are located among the Sr ions of the first subsystem. The atomic positions are modulated along the c axis by the interactions between the two subsystems

A new composite crystal of [Ba]x[(Pt, Cu)O3] (x = 1.317) grown by the flux method using CuO as flux

A new complex oxide in the BaPtCuO system has been found during single crystal growth of a high-Tc oxide superconductor ErBa2Cu3O7−x using CuO as a self-flux in a Pt crucible. This Pt complex oxide is easily formed in air without high O2 pressure. The existence of Ba2+, a strong basic cation, in the melt is found to be strongly effective for stabilization of this compound. The chemical composition of the crystal is Ba4.0Pt1.7Cu1.1Ox. The chemical formula is [Ba]x[(Pt, Cu)O3] (x = 1.317). It takes a unique composite crystal structure. The first subsystem is [Ba] and the second is [(Pt, Cu)O3], the superspace group is RP31c111:PR3m1s′. The first subsystem [Ba] is located in the channels of the second columnar subsystem [(Pt, Cu)O3] parallel to the c axis. The lattice parameters are a = 5.817(2), c = 4.233(1) A, k = (a∗ + b∗)3 + 1.519(1)c∗, V = 124.0 A3, Z1 = 2, Z2 = 3 and Dx = 7.46 g cm−3.

Crystal growth and properties of R2Ba2CuPtO8 (R = Ho, Er, Y), R2Ba3Cu2PtO10 and Ba4CuPt2O9

Abstract Three new Pt complex oxides have been identified as products of the CuO-flux growth of R-Ba-Cu-O superconducting oxides in platinum crucibles. A growth mechanism for the three Pt compounds involving incorporation of Pt from the crucible is proposed. The crystal structure of R 2 Ba 2 CuPtO 8 has been determined and its relationships to physical properties are discussed.

Growth and characterization of Va-Sn-Ga (Va = Ta, Nb, V) superconducting compounds

A systematic study of Va-Sn-Ga (Va = Ta, Nb, V) ternary systems has been made from the point of view of crystal growth, crystal structure and physical properties. Applying the self-component flux method where molten tin acted as a solvent, single crystals of new ternary intermetallic compounds Ta5SnGa2, Nb5Sn2Ga and V5Sn5Ga3, were successfully synthesized. The crystal structures of Ta5SnGa2 and Nb5Sn2Ga are very similar each other: both of them belong to the tetragonal system (space group: 14/mcm) and are isostructural with W5Si3. In contrast to them, V5Sn5Ga3, is orthorhombic (space group: Acam) and crystallizes in a new structural type. Superconducting transitions have been observed in Ta5SnGa2 and Nb5Sn2Ga crystals at 1.80 and 1.75 K.

Flux growth of a new ternary superconducting crystal Nb5Sn2Ga

Abstract Single crystals of a new ternary intermetallic compound Nb5Sn2Ga were obtained by the flux method using molten tin as a solvent. The crystal structure is tetragonal (space group D184h-I4/mcm) and isostructural with Nb5Sn2Si. This compound exhibits metallic conductivity and shows a superconductive transition at Tc = 1.75 K. The residual resistivity ratio RRR=ρ(293 K)/ρ(4.2 K) is ≅12. This is the first investigated compound belonging to the ternary Nb-Sb-Ga system.

Flux growth and crystal structure determination of trilithium niobate

Abstract Single crystals of trilithium niobate, Li3NbO4, have been grown for the first time by a slow-cooling flux method using LiCl as a flux. Single crystals are transparent colourless cubes with 100–600 μm edges. The crystal structure of Li3NbO4 has been determined from single crystal X-ray data. This compound belongs to a cubic system, space group I 4 ¯ 3 m , the unit cell dimensions are a = 8.412(2)A, V = 595.2(4)A3 and Z = 8. The structure comprises characteristic Nb4O16 clusters which form a body-centred cubic lattice with Li ions located among the Nb4O16 clusters. The R factor (wR) is 0.045. Well-developed facets of the crystals are {100}. The X-ray and pycnometric densities are in good agreement: Dx = 3.967 mg m−3 and Dm = 3.95 mg m−3 respectively. The space group presented here contradicts that reported by previous researchers.

Growth and Superconductivity of a New Ternary Intermetallic Compound, Ta5Ga2Sn

A new ternary intermetallic compound, Ta5Ga2Sn, has been synthesized by the self-flux method using molten tin as a solvent. The crystal structure is tetragonal (space group D4h18/I4 mcm). The lattice parameters are a=10.342(2) A, c=5.174(2) A, V=555.3 A3, Z=4, and the X-ray density Dx is 13.91 Mgm-3 at room temperature. This compound exhibits superconductivity at Tc= 1.80 K (midpoint), ΔTc 220 mK by ac-susceptibility measurement and dc 4-terminal electrical measurement.