Properties of the Bi-surplus superconducting Bi2.1−xPbxSr2Ca2Cu3Oy compounds

Abstract Properties of the Bi-surplus superconducting Bi 2.1− x Pb x Sr 2 Ca 2 Cu 3 O y ( x =0.00–0.60) compounds have been investigated. It is found that Pb plays a very important role in the formation of the superconducting phases with high purity and especially in promoting and enhancing the stability of the 2223 phase in (Bi,Pb)–Sr–Ca–Cu–O compounds. By increasing the duration of the heat treatment, the single-phase region will be widened, while the transition temperatures and values of zero-resistance remain nearly unchanged. With suitable heat treatment, the 120 K high- T C phase can be synthesized by the solid-state reaction method. The superconducting fraction reaches a maximum in the compounds with x =0.30–0.60. Special attention is paid that the superconducting state is destroyed by annealing in vacuum for the compound with x =0.40.