ON THE ROLE OF BI2SR2CA1CU2O8 AND BI2SR2CU1O6 ON THE WEAK LINKS AND CRITICAL CURRENTS IN (BI,PB)(2)SR2CA2CU2O10 AG SUPERCONDUCTING TAPES/

Silver-sheated (Bi,Pb)(2)Sr2Ca2Cu3O10 (Bi2223) Superconducting tapes w ith different Bi2Sr2Ca-Cu2O8 (Bi2212) and Bi2Sr2Cu1O6 (Bi2201) concent rations, were prepared by using a two-step sintering processing and by varying cooling rates in the fabrication of the superconductors. The effect of res:dual Bi2212 and Bi2201 phases on weak links and critical currents of the Bi2223;Ag tapes was investigated. It was found that r esidual Bi2201 caused weak links at grain boundaries and limited the c urrent-carrying capacity of the tapes. Comparatively, the residual Bi2 212 phase had much less influence on both weak links and critical curr ents. Elimination of Bi2201 by sintering tapes at a low temperature in the final thermal cycle, or by cooling the tapes slowly, increased cr itical current by a factor of two. Flux pinning property was also impr oved by removing the residual Bi2201 phase. (C) 1998 Elsevier Science Ltd. All rights reserved.