We have investigated hot-drawn PbMo6S8 composite monofilament wires (J(c) = 4.6 x 10(8) A/m2 at mu0H = 10 T and T= 4.2 K) in particular steps that occur in the I-U transition curves. These steps have been measured in fields up to 9 T and in a temperature range between 2 K and 10 K. We have analysed them by considering two models, the hot spot model and the phase-slip model. Furthermore, a flux flow channel picture is developed, where the step is related to an avalanche of flux flow localised in a narrow channel. The observed field dependence of the step in a field applied transversally to the wire can be understood within this description. All these model considerations concur; the origin of the steps appears to lie in local defects with a mum length-scale. Just a few of these defects may already depress the overall critical current in a substantial way. Taking into account this situation, there exists an important potential for further improvements of the critical current in PbMo6S8 wires.

The application of PbMo6S8 wires for the generation of steady state magnetic fields in excess of 20 Tesla needs several conditions to be fulfilled in order to be realistic. In this paper we report about practical design considerations for PbMo6S8 wires. Besides the availability of wires with sufficient lengths and uniform high critical current density J(c), thermal and mechanical stability has to be achieved. The most severe criterion for thermal stability is based on the prevention of flux jumps in the presence of screening currents in the adiabatic limit. This results in filament diameters between 710 mu-m and 90 mu-m for a critical current density of 5x10(8) A/m2 and 2x10(9) A/m2, respectively. A dynamic stabilization of a PMS wire in an epoxy impregnated coil is not very efficient. Finally the behavior of J(c) of PbMo6S8 wires under tensile and compressive stress will be discussed.

Crucible corrosion is one of the major obstacles to obtaining large crystals of the high-temperature superconductor YBa2Cu3O7-x. The crucible-melt interfaces of three types of ceramics (alumina, zirconia and tin oxide) have been studied in order to understand the corrosion mechanism. This may help to reduce the crucible problem in crystal growth of YBCO and to indicate alternative crucible materials of improved corrosion resistance.

The superconducting transition temperatures of compounds RE5Os4Si15 have been measured as a function of hydrostatic pressure up to 1.4 GPa. Transition temperatures decrease linearly, with pressure coefficients ranging from 0.6 to 1.1 K/GPa. Across the series, the variation of Tc due to the change in unit cell volume and the effect of magnetic pairbreaking are of similar magnitude but opposite sign. We obtain a characteristic product N(EF)I2 = 2· 10−4eV which is approximately twice the value obtained when volume effects are neglected.

Abstractis presented for the complete composition range.

AbstractSingle‐crystal data are reported for the title compounds.

The osmium-silicon phase diagram was investigated by means of X-ray powder diffraction, differential thermal analysis, metallography, microprobe analysis and electrical resistivity measurements. The existence and type of formation of the following intermetallic compounds was established: OsSi, Os2Si3 and OsSi2. These three compounds are semiconducting. A metastable phase was found at 67 at.% silicon.

Single-crystal X-ray data (Mo Kα radiation) are reported for the following: 1.(i) Y3Os4Si12 (orthorhombic, Er3Ru4Si12 structure type, oS76, Cmca, a = 18.495(2) Å, b = 8.125(1) Å, c = 8.130(1) Å, V = 1221.7 Å3, Z = 4, Dx = 7.417 g cm−3, R = 0.096 for 927 contributing independent reflections);2.(ii) Y5Os4Si14 (monoclinic, Lu5Co4Si14 structure type, mP46, P21/c, a = 12.779(5) Å, b = 8.019(3) Å, c = 7.926(3) Å, β = 98.69(3)°, V = 802.9 Å3, Z = 2, Dx = 6.611 g cm−3, R = 0.076 for 2336 reflections);3.(iii) Y9Os4Si20 (monoclinic, new structure type. mP66, P21/c, a = 19.417(1) Å, b = 7.949(3) Å, c = 8.005(3) Å, β = 95.92(1)°, V = 1229.0 Å3, Z = 2, Dx = 5.735 g cm−3, R = 0.069 for 1840 reflections).

AbstractOn the basis of this extensive reinvestigation, an accurate equilibrium phase diagram of the entire Zr‐Rh system is presented.

The phase relations in the ZrRh system were reinvestigated by differential thermal analysis, levitation thermal analysis, X-ray analysis electron microprobe analysis, microstructural examinations and measurements of the superconducting transition temperatures. A new complete phase diagram is presented. Owing to the occurrence of martensitic transformations; the central part of the diagram is particularly complicated. Observed enthalpies of formation are given for three intermediate compounds.

The YOsSi system contains two Si-rich phases with superconducting transition temperatures of 10.8 and 9.8 K respectively. The first phase was also found to exist if Y was replaced by Er, Ho, Dy or Tb. We have studied the influence of these magnetic rare-earths on Tc by applying the results foreseen by the Abrikosov-Gor'kov theory. There are several indications that Tc might depend on dimensional parameters. For the second phase only the TmOsSi system provided a superconducting isotype.

The existence of six new ternary phases has been established in the silicon-rich part of the Y–Os–Si system. At least two of these phases are superconducting with critical temperatures of 10.5 K and 9.7 K which are the highest transition temperatures observed for ternary silicides. The crystal structure of these phases appears to be closely related to the Lu5Co4Si14-type structure. Structure drawings of two of the phases with new structure types are included.