One of the main purposes of this study is to clarify the conditions for growing relatively large crystals of Nb5Sn2Ga from high temperature tin solution in a He gas. The temperature of a mixture of raw materials was raised at a rate of 400degreesC h(-1) up to 1400degreesC and kept for 10 h, and then slowly cooled down to room temperature. The single crystals of Nb5Sn2Ga were generally obtained as prisms elongated in the (001) direction and with {100} and {110} faces parallel to the (001) direction of the tetragonal system. The largest crystals prepared have maximum dimensions of about 1 X 1 X 10 mm(3). Nb5Sn2Ga has a tetragonal symmetry with a=1.0586(2) nm, c=0.5177(1) nm, space group I4/mcm and ordered W5Si3 type structure. The compound shows superconductivity at T-c=1.75 K and DeltaT(c)=140 mK. The Vickers microhardness value on {001} plane and {100} or {110} planes of crystals is in the range of 8.5-10.1 GPa. The oxidation of Nb(5)Sn2Ga crystal starts at about 562degreesC. The final oxidation products were NbO2, Nb12O29, Nb2O5, SnO2 and Ga2O3, respectively.

Large crystals (up to 2×1×0.5mm) of a new C70–sulphur compound were grown by evaporation of a benzene solution. The composition of this compound was determined by chemical analysis to C70S8. Single-crystal and X-ray powder diffraction experiments showed that the phase has orthorhombic structure with cell parameters a=30.18, b=30.41, and c=28.32Å and the space group Pbcn. The Raman spectrum from the new compound was very similar to those of pure C70 and sulphur with the exception of some changes in relative intensity and small shifts of a few peaks at wavenumbers below 500cm−1. The results suggest that the C70–S8 interactions mainly consists of weak van der Waals bonds. Some irregularities in the peak shifts suggest that the distribution of S8 rings around the C70 molecules are less symmetrical that in the well-known C70S48 phase.

The crystal structure of V2B3 was reinvestigated using single-crystal X-ray diffractometry. V2B3 crystallizes in the orthorhombic space group Cmcm with a = 3.0599(4) Angstrom, b = 18.429(2) Angstrom, c = 2.9839(4) Angstrom, Z = 4. The crystal was grown from a high temperature aluminium melt with vanadium metal chips and boron powder as starting materials. The structural parameters of V2B3 were refined with a full-matrix least-squares program to a final R(F-2) value of 0.024 for 984 unique reflections. The influence of atomic radii of transition metal elements on the unit cell parameters is discussed.

An orthorhombic modification of TlCu4Se3 was synthesised at room temperature by oxidative copper extraction from TlCu5Se3. It crystallises in a new structure type, space group Pnnm, with the cell parameters a = 12.4306(2) Å, b = 12.7997(2) Å, c = 3.93516(6) Å. The structure is closely related to the tetragonal structure of the parent compound. For the structure solution direct methods were used on single-phase Guinier-Hägg X-ray powder film data. In the refining stage, the Rietveld method was applied on powder diffractometer data. After being heated above 670 K, this orthorhombic form completely transforms to the tetragonal modification. Both are metallic conductors.

LiCuO2 was synthesized at room temperature by delithiation of Li2CuO2 using bromine in acetonitrile. The product shows broad diffraction profiles which were analysed by the Rietveld refinement technique on X-ray and neutron powder data. The phase conforms to the NaCuO2 structure type (C2/m, Z = 2) with the cell a = 5.733(1) angstrom, b = 2.7176(3) angstrom, c = 5.622(1) angstrom, beta = 120.68(2)-degrees.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Single crystals of ErRh311B2 were grown using the high temperature solution method. The crystal structure was determined and refined by the powder technique. The compound crystallizes in the space group C2m with cell dimensions a = 5.3561(4) Å, b = 9.2819(7)Å, c = 3.1013(3) Å and β = 90.898(8)°. The final unweighted profile R value is 6.4% and the conventional Bragg R value 4.8%. Magnetic measurements indicate ferromagnetic order below TC = 27 K, but the magnetic data show considerable anisotropy. The highly anisotropic magnetic properties are probably due to the Er atom chains along the c axis.

Single crystals of the new phase TmAlB14 were grown using the high-temperature solution method. The crystal structure of TmAlB14 was refined from X-ray powder diffraction data using the Rietveld method. The structure is of MgAlB14-type with the space group Imma and unit cell parameters a = 5.8212(3) angstrom, b = 10.3837(2) angstrom and c = 8.1762(3) angstrom. The final, conventional R-value and profile R-value are 0.031 and 0.064, respectively. The structure is characterized by a partial occupancy of both metal positions and a splitting of the thulium atomic position.

The crystal structures of Y0.62Al0.71B14 and Er0.62Al0.73B14 belong to the MgAlB14 type structure. The refinements are based on the space group Imma and converged at the conventional R values 5.0% (2908 reflections) and 3.4% (2394 reflections) reflections) respectively. The cell dimensions of the single crystals are a=5.8212(3) Å, b=10.4130(8) Å, c=8.1947(6) Å and a=5.8200(1) Å, b=10.3950(4) Å, c=8.1825(3) Å respectively. Important structural characteristics are partial occupancy of both metal positions and a splitting of the rare earth atomic position.

Synthetic and process studies of the new high-Tc super-conductors are carried out using the methods of powder technology. The equipment for these studies at the Institute of Chemistry, University of Uppsala is described. The laboratory is equipped with jaw crusher, various mills, powder mixer, spray dryer and several sintering furnaces. The laboratory has excellent facilities for powder characterization, such as a semi-automatic image analyzer, a system for X-ray line broadening analysis, BET apparatus, sample divider and a sieving machine. Single-crystal growth experiments are also reported. Single crystals of YBa2Cu3O7 and Bi2Sr2CaCu2O8 were grown by the off-stoichiometric method. The largest crystals of YBa2Cu3O7 were obtained with the soaking temperature of 980°C and a cooling rate of 2°C h−1. A soaking temperature of 925°C and a cooling rate of 40°C h−1 produced the largest Bi2Sr2CaCu2O8 single crystals. A single crystal examination showed that the structure of Bi2Sr2CaCu2O8 is incommensurate along the b axis. The lattice parameters were a = 5.40 Å, b = 25.25 Å, c = 30.62 Å.

The structure of the new boride Ta5B6 has been determined and refined using single-crystal X-ray diffraction techniques. The structure is described in the space group Cmmm with a = 22.602(8) Å, b = 3.1385(7) Å and c = 3.2895(4) Å. The refinement is based on 408 non-equivalent reflections and the final, conventional R value for these reflections is 2.34%. The structure is of the V5B6 type. The present structure refinement is the first single-crystal study of a phase crystallizing in the V5B6-type structure.

AbstractSingle crystals of Ta5B6 are obtained by slow cooling of a solution of Ta and B in molten aluminum.

Single crystals of a new compound Ta5B6 was prepared by the high temperature aluminium solution method using tantalum and boron powder as starting materials in an argon atmosphere. The experimental conditions for obtained single crystals of relatively large size were established. The optimum conditions for growing Ta5B6 single crystals were found to include atomic ratios of starting materials B/Ta=1.2 and Al/Ta=8.38, soaking temperature 1650°C, soaking time 5 h and a cooling rate of 25°C h−1. Single crystals of Ta5B6, having a grey color and metallic luster, were generally obtained in the form of an irregular or trapezoidal shape: the latter crystals were enclosed by two large {010} planes. The largest crystals prepared have maximum dimensions of about 0.12mm×0.13mm×0.23mm. The crystals are orthorhombic with a space group of either Cmm2, Cm2m, C222, or Cmmm and the unit cell dimensions a=3.1385(10) Å, b=22.609(7) Å, c=3.2865(8) Å, and V=233.20(12) Å3. The X-ray density is 13.808(2) g cm−3. The present study of growing Ta5B6 crystals is the first single crystal growth study of a V5B6 type crystal.

Abstract Single crystals of a new compound Ta5B6 was prepared by the high temperature aluminium solution method using tantalum and boron powder as starting materials in an argon atmosphere. The experimental conditions for obtained single crystals of relatively large size were established. The optimum conditions for growing Ta5B6 single crystals were found to include atomic ratios of starting materials B/Ta=1.2 and Al/Ta=8.38, soaking temperature 1650°C, soaking time 5 h and a cooling rate of 25°C h−1. Single crystals of Ta5B6, having a grey color and metallic luster, were generally obtained in the form of an irregular or trapezoidal shape: the latter crystals were enclosed by two large {010} planes. The largest crystals prepared have maximum dimensions of about 0.12mm×0.13mm×0.23mm. The crystals are orthorhombic with a space group of either Cmm2, Cm2m, C222, or Cmmm and the unit cell dimensions a=3.1385(10) Å, b=22.609(7) Å, c=3.2865(8) Å, and V=233.20(12) Å3. The X-ray density is 13.808(2) g cm−3. The present study of growing Ta5B6 crystals is the first single crystal growth study of a V5B6 type crystal.

The structure of a crystal with the composition AlB31, prepared by arc-melting crystals of α-AlB12, has been investigated by single-crystal X-ray diffractometry. The space group is R3m (No. 166) with the hexagonal cell dimensions a = 10.965(1) Å and c = 23.868(2) Å. The structure was refined by a fullmatrix least-squares program to an R(Rw) value of 0.034(0.040). The three-dimensional boron framework of the crystal is essentially equivalent to that of β-rhombohedral boron. The aluminum atoms partially occupy A1 and D holes in the boron framework, and in the D hole the aluminum atoms are distributed over five positions. A disordered structure around the single B(15) atom site is discussed in connection with the Al distribution in the D hole.