Formation Mechanism of (Bi, Pb)2Sr2Ca2Cu3O10 Phase and Critical Current in Silver Clad Superconducting Tape

Abstract

X-ray diffraction method was used to characterise the phase composition and investigate the formation mechanism of the (Bi,Pb)2Sr2Ca2Cu3O10 phase from the precursor with (Bi,Pb)2Sr2CaCu2O8 as the main phase. The reaction is found to be a two-dimensional nucleation (random)-growth type, (-(ln(l-F))1/2=kt, where F is the conversional fraction of (Bi,Pb)2Sr2CaCu2O8 and t is the sintering time. The critical current of the tape is quantitatively related to the conversional fraction of (Bi,Pb)2Sr2CaCu2O8 to (Bi,Pb)2Sr2Ca2Cu3O10 phase. In low fraction regime of (Bi,Pb)2Sr2CaCu208, the critical current of a tape shows no clear dependence on remaining (Bi,Pb)2Sr2CaCu208 phase, other factors such as grain alignment, colony size, contact between colonies, and fine nonsuperconducting particles become important in controlling the Jc. Also, in this regime, the predominant weak links seems to be the colony boundaries rather than (Bi,Pb)2Sr2CaCu208 phase.