Preparation of High-Tc Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O Superconductors

Abstract

Bulk superconductors of the Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-0 systems have been investigated to clarify their superconducting properties. In the Bi-Sr-Ca-Cu-0 system, its superconducting properties were improved by doping Pb0 after the calcination; the high-T_c phase (105 K) was formed during the sintering process and stabilized down to room temperature. Zero-resistance was realized at 104 K for 5wt% Pb0 doped BiSrCaCu₂O_x sintered at 848°C for 72 h in air. In the Tl-Ba-Ca-Cu-O system, its superconducting properties were found to be significantly sensitive to the sintering temperature and the composition of the starting materials. Zero-resistance was achieved at 118 K for Tl₂Ba₂Ca₂Cu₃O_x sintered at 880°C for 1 h in O₂. In addition, an ac susceptibility result also supports its superconductivity with high critical temperature.