Preparation,Microstructure and Properties of Ag-sheathed Bi(Pb)-Sr-Ca-Cu-O Superconductor Tapes

The process to obtain high T（110K）phase quickly,the microstructure and properties of Ag-sheathedBi（Pb）-Sr-Ca-Cu-O superconductor tapes have been studied.It was found that the formation time of the highTc phase was greatly shortened by the addition of more Ca and Cu to the nominal composition of Bi（Pb）:Sr:Ca:Cu=2:2:2:3 and the adoption of appropriate sintering temperature and cooling rate.Superconductor powder with predominant high T,phase was prepared after a 840 C/50 h treatment.The Jof the Ag-sheathed tapes and the magnetic field dependence of Jwere obviously improved by repeatedly pres-sing and sintering.The maximum transport current density at 77K in a zero magnetic field was 12,200 A/cm2.The magnetic dependence of Jwas summarized as follows:6.450 A/cm2（B⊥1.B∥S.0.1T）1,810 A/cm2（B⊥1.B∥S,1T）,390 A/cm2（B⊥1.B∥S,2T）（B:magnetic field.1:electric current.S:surface of tapes）.Theimprovement of Jwas attributed to the formation of the plate-like structure with homogeneous compositiondistribution and the strong c-axis texture.