Improved critical current density and irreversibility line in HIP'ed Chevrel phase superconductor PbMo6S8

Flux penetration measurements have been made from 4.2 K up to T-c in DC magnetic fields up to 10 T on Hot Isostatically Pressed (HIP'ed) and unHIP'ed samples of PbMo6S8 (PMS). Fabricating at 2x10(8) Nm(-2) increases the critical current density (J(c)) by a factor of typically 20 to greater than 4 X 10(8) Am-2 at 5 T and 6 K and the irreversibility line by a factor of almost 2, so that for HIP'ed PMS the irreversibility line lies very close to mu(O)H(C2)(T) values determined from reversible DC magnetisation measurements. An analysis of the J(c) data using Kramer's universal scaling law gives a calculated value of J(c) at 10 T and 4.2 K of 4 x 10(8) Am-2 and a value for the irreversibility field of 39 T at 4.2 K. It is suggested that the increase in J(c) produced by the HIP process, is due to increasing the contact area between the grains by increasing the density, and improving the superconducting properties at the grain boundaries.