Sintering period dependence of composition and superconducting properties of (BiPb)SrCaCu,1.8Ox system

The material system (Bi_0.7Pb_0.3)Sr₁ Ca₁ Cu_1.8O _x forms, at 840° C, two major phases having a highT _c (100K) and a lowT _c (70 K) both of which consist of platelets and a non-superconducting minor phase which has a rod-like shape and is isolated by the major phases. As the sintering period increases, the amount of highT _c phase increases accompanying the decrease in lowT _c phase while the amount of the non-superconducting phase is independent of sintering period, resulting in a superconductor withT _c of 100 K. Changes in compositions of each phase also occur during sintering due to evaporation of bismuth and lead.