Zero resistance above 100 K in Bi-based superconductors

The authors have concentrated on the effect of Pb on the superconducting properties of the Bi-Sr-Ca-Cu-O system. Preliminary results are also presented on the effect of varying the Sr:Ca and Bi:Ca ratios in Pb-substituted samples. It is shown that the addition of Pb does not guarantee a step-free resistive transition. The steps in the resistivity become more pronounced as the Bi:Ca ratio is increased. This gradual, systematic change suggests that the reduced continuity is not the result of an abrupt reduction in the c-spacing near grain boundaries as observed in Pb-free samples.<
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