ENHANCED FLUX-PINNING IN AG-SHEATHED (BI,PB)2SR2CA2CU3O10+DELTA TAPES BY POSTANNEALING

A significant enhancement of J(c) in a magnetic field for Ag-sheathed Bi-Pb-Sr-Ca-Cu-O (BPSCCO) tapes has been achieved by post-annealing at reduced temperature after processing. This post-annealing at reduced temperature introduced extra oxygen into the oxide superconductor. Weak links were eliminated and J(c) has been increased in the post-annealed tapes by a factor of 1.5 to 3 at 0 T over the normally processed tapes without post-annealing. The optimized J(c) values for the post-annealed tapes ranged from 30 000 to 57 000 A CM-2 at 77.3 K and 0 T. The irreversibility lines measured by a DC SQUID exhibited an improvement in flux pinning in the post-annealed tapes compared with that in normally processed tapes. The introduced oxygen ions are responsible for the enhanced J(c) and may affect two dimensionality in superconductivity for the BPSCCO system.