Superconductivity of Bi2Sr2Ca2Cu3PbxOy (x=0.2, 0.4, 0.6)

The addition of Pb to the superconducting Bi-Sr-Ca-Cu-O system is found to increase the volume fraction of the high-T c phase (T c>100 K) determined by the ac susceptibility and the X-ray powder diffraction pattern. It also lowers the optimum firing temperature to produce the high-T c phase. The peaks attributed to the high-T c phase in the X-ray diffraction pattern become sharper, which indicates that the addition of Pb promotes crystallization. It is found by differential thermal analyses that Pb also acts as a flux.