Effect of Additive Oxides with "Inert Pair" Elements on the Formation of the High-Tc Phase in the Superconductor of Bi-Sr-Ca-Cu-O system

Abstract

Specimens of M₂.₂Sr₂.₀Ca₂.0Cu₃._zO_y [M₂.₂=Bi₁.₈Pb_0.4-x Inx and Bi₁.₈Pb_0.2M'_0.2 (M'=Sn, Sb and Y)] were sintered at 855°C for 40-96hr after decarbonation in air atomosphere and their resistance-temperature curves were compared in order to investigate effects of "inert pair" elements on the formation of the high-Tc phase. In low level of In content (x-value) below 0.18, the stabilization of the high-Tc phase by incorporation of Pb remained almost unaffected. The step wise (shoulder-like) drop in resistance curves due to the coexistence of high and low- Tc phases was observed on specimens of In_0.2, Sn_0.2 and Sb0.2, showing that lighter inert pair elements have poorer tendency to stabilize the high-Tc phase. The specimen of Y_0.2 showed disappearance of the high-Tc phase as well as in specimens of In_0.4 without Pb.