The effects of Ba addition and grinding time on Tc of the high-Tc phase in the Bi-Pb-Sr-Ca-Cu-O system have been studied. Samples with compositions of Bi:Pb:Sr:Ba:Ca:Cu=0.9:0.2:1.0:X:1.0:1.6(X=0-0.05) were prepared by grinding the high-Tc phase and BaCO₃ powders for various periods (20 to 120min). The high-Tc phase degraded with grinding time. In samples of a composition of X=0.05 heated at 845≥C for 60h in air, a small amount of the low-Tc phase and Bi₃(Sr, Ba)₄Ca₃O_z besides the high-Tc phase were formed. The heating led to the grain growth of the high- Tc phase with increasing grinding time. However, Tc(R=0) was decreased due to the formation of the low-Tc phase and Bi₃(Sr, Ba)₄Ca₃O_z.
In a sample with X=0.05 heated at 850°C for 60h in air, only a solid solution of the high-Tc phase was formed. Tc(R=O)=125K was attained in this sample. The Meissner diamagnetic response at 125K was confirmed by SQUID, but the volume fraction of the 125K phase was estimated below 1%.