Reaction Mechanism of Forming the High-Tc 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 Bi₂Sr₂CuO _x are obtained from the disproportionation reaction of the low-T _c phase. Bi₂Sr₂CuO _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.