Properties of the Bi-surplus superconducting Bi2.1-xPbxSr2Ca2Cu3Oy compounds
Properties of the Bi-surplus superconducting Bi2.1-xPbxSr2Ca2Cu3Oy (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-TC 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. © 2003 Elsevier Science B.V. All rights reserved.