Reaction Mechanism of Forming the High-T_c Superconductor in the Pb-Bi-Sr-Ca-Cu-O System

Abstract

A relationship between synthesized phases and starting compositions has been studied in the Pb-Bi-Sr-Ca-Cu-O system. The reaction step of forming the high- T c phase ( T c ∼110 K) has been presumed as follows. Firstly, the high- T c phase and Bi 2 Sr 2 CuO x are obtained from the disproportionation reaction of the low- T c phase. Bi 2 Sr 2 CuO x and residual Ca and Cu atoms melt into the PbO flux. The low- T c phase is precipitated from the melt. The formed low- T c phase causes a further disproportionation reaction. The high- T c phase is produced in large quantities by repeating the cycle.