Effect of Ba Addition on the Formation of the High-Tc Phase in the Bi, Pb-Sr-Ca-Cu-O System

Abstract

The effect of Ba addition on the formation and the critical temperature Tc of the high-Tc superconductor in the Bi, Pb-Sr-Ca-Cu-O system was studied. A series of samples Bi_0.7Pb_0.3Sr_1-αBa_αCaCu_1.8O_x were prepared by the conventional ceramic method. High-Tc phase ( c ≅ 37Å ) was formed without coexistance of low-Tc phase ( c ≅ 30Å ) and 24Å phase in the sample of α ≤ 0.5 by the heat treatment at 845°C for 45-140h even though BaPb_0.75Bi_0.25O₃ and (Sr, Ca)₃Cu₅O_x were a little remained. The electrical resistance of the sample with a composition of α=0.1 heated at 845°C for 140h dropped to zero at 105K and diamagnetic response was also observed. It was found that the addition of a small amount of Ba promoted the formation of high-Tc phase but Ba²⁺ ion was hardly substituted in the high-Tc phase.