Effects of Starting Composition and Treating Atmosphere on Phase formation, Microstructure and J_c of Bi_2Sr_2CaCu_2O_x/Ag Multilayer Tapes

摘要

The Bi-2212/Ag tapes with nominal composition of Bi_2Sr_(20.5)Ca_(0.95)Cu_2O_x and Bi_2Sr_(2.05)Ca_(0.8)Cu_(1.8)O_x have been prepared by PAIR process and melt-solidification process in the atmosphere of oxygen and air. The result shows the starting composition and treating atmosphere, mainly affecting on the amount of extra phases (Bi-free, Cu-free phases), play an important role in the microstructure and J_c of the tapes. In treating in pure oxygen, the reduction of extra phases and highest Jc of over 5.0X10~5 A/cm~2 at 4.2 K, 10 T is obtained in Bi_2Sr_(2.05)Ca_(0.95)Cu_2O_x/Ag tape, while in treating in air, reduction of extra phases and higher J_c of 4.0X10~5 A/cm~2 is obtained in Bi_2Sr_(2.05)Ca_(0.8)Cu_(1.8)O_x/Ag tape than Bi_2Sr_(2.05)Ca_(0.95)Cu_2O_x/Ag tape.