Chevrel phase (Pb/sub 1-x/Cu/sub 1.8x/)Mo/sub 6/S/sub 8/ with a mixed structure and high critical parameters

Abstract

Bulk polycrystalline materials of the quaternary superconducting Chevrel phase (Pb/sub 1-x/Cu/sub 1.8x/)Mo/sub 6/S/sub 8/ with x=0.00, 0.05, 0.10, 0.30, 0.50 and 1.00 have been fabricated using HIP'ing at a pressure of 2000 bar and a temperature of 800/spl deg/C for 8 hr. The phase structure and hexagonal lattice parameters (c, a) have been studied using X-ray diffraction. Resistivity and susceptibility measurements have been made in magnetic fields up to 15 T and temperatures from 3.5 K to 18 K. The ternary Chevrel phase compounds PbMo/sub 6/S/sub 8/ and Cu/sub 1.8/Mo/sub 6/S/sub 8/ have been fabricated with high c/a ratio and critical temperature (resistive midpoints of 14.8 K and 11.1 K respectively). When x/spl les/0.1, quaternary materials are almost single phase. When x>0.1, the quaternary material are a two-component mixture of PbMo/sub 6/S/sub 8/-like and Cu/sub 1.8/Mo/sub 6/S/sub 8/-like structures. The materials have broad transitions with calculated upper critical field values for 0 K of /spl sim/40 T determined from the midpoint of the resistive transition.