DEPENDENCE OF CRITICAL-CURRENT DENSITIES IN CHEVREL-PHASE SUPERCONDUCTING WIRES ON MAGNETIC-FIELDS UP TO 25-T

V-I characteristics have been measured, in several monofilamentry Chev rel phase superconductors (CPS) wires made using prereacted powders of both pure SnMo6S8 (SMS) and Pb0.6Sn0.4Mo6S8 (PSMS) compounds, in appl ied magnetic fields up to 25 T. The values of J(c) in different wires lie in the range similar to 5 x 10(7)-10(9) A/m(2) at 4.2 K and 9 T. I n the SMS wires the critical current density J(c)(B) tends to vanish a t the expected ideal B-c2. In contrast, for PSMS wires the J(c)(B) ten ds to vanish at fields much smaller than the expected B-c2 for pure Pb Mo6S8 (PMS) and nearer to that of the SMS. The V-I characteristics at the dissipative onset are highly non-linear and show a power law behav iour V = kI '' with a typical n-value (1.8 K, 25 T) > 17.