Influence of Calcining Temperature on Formation of the High-Tc Phase in the Bi-Pb-Sr-Ca-Cu-O System

Abstract

The influence of the calcining temperature on the formation of the high-Tc phase and the electrical conductivity has been studied for the sample with a nominal composition of Bi_0.96Pb_0.24Sr_1.0Ca_1.1Cu_1.6O_x. The product in the sample calcined at 680°C was much different from that in the sample calcined at 800°C. Namely, Bi_0.46Ca_0.54-ySr_yO_z(0.1<y<0.2), Bi₁₀Ca₇O₂₂, Ca₂PbO₄, SrCO₃ and CuO were formed at 680°C, while the low-Tc phase and Ca₂PbO₄ were mainly formed at 800°C. At 850°C, the fraction of the high-Tc phase increased more quickly in the sample calcined at 680°C than in the sample calcined at 800°C, and mostly monophasic high-Tc phase was obtained by the sintering at 850°C for 24h after the calcination at 680°C, however, that sample showed lower Tc_(zero)=87K than the sample calcined at 800°C.