Improved high-field performance of Pb sub 1 minus x Sn sub x Mo sub 6 S sub 8 ribbons

This paper describes the effect of Sn additions to PbMo{sub 6}S{sub 8} ribbons. These ribbons are produced via a vapor-transport technique. Small amounts of Sn in Sn{sub 1{minus}{ital x}}Pb{sub {ital x}}Mo{sub 6}S{sub 8} alloy ribbons provide a significant ({similar to}10{times}) increase in {ital J}{sub {ital c}} at high fields over that obtained with PbMo{sub 6}S{sub 8} alone. Critical current densities of 1{times}10{sup 4} A/cm{sup 2} at 4.2 K near 20 T have been achieved for compositions with {ital x} near 0.5. The low {ital J}{sub {ital c}}'s in PbMo{sub 6}S{sub 8} appears to be related to the presence of a large fraction of a nonsuperconducting triclinic phase resulting from a partial phase transition at cryogenic temperatures. This phase transition is partially suppressed with Sn additions, resulting in an improved performance.