MAGNETIC-PROPERTIES AND MICROSTRUCTURES IN AG-CLAD BI-PB-SR-CA-CU-O WIRES

High critical current density (J(c)) and improved J(c)-magnetic field dependence have been achieved in Ag-clad (Bi, Pb)2Sr2Ca2Cu3O10+x (2223) wires through the use of the following parameters: solution methods for powder production, mechanical deformation for densification and grain alignment, and microstructural and compositional control for enhancement of flux pinning. Complex AC susceptibility measurements under DC magnetic fields revealed that the irreversibility temperature scaled with the applied field according to H1/3, in contrast with YBa2Cu3O7-x but in accordance with bulk Bi-based and Tl-based materials. The pinning potential in Ag-clad Bi-based wires was estimated to be 0.31 eV at 77 K and 1 T. Results for the J(c), AC susceptibility, and X-ray diffraction indicate that the presence of a fraction of highly dispersed low-T, (Bi, Pb)2Sr2CaCu2O8+x (2212) has a beneficial effect on flux pinning, suggesting that the 2212 phase may act as a potential pinning centre in these materials, which show microstructures of intergrown 2223/2212. A high density of dislocations was observed to have a Burgers vector [110] and magnitude of 1/2 [110]. The effect of defects on flux pinning is discussed.