Phase evolution during post-annealing and its influence on critical currents of (Bi,Pb)-2223/Ag tapes

摘要

Post-annealing (PA) has been performed on fully reacted multifilamentary (Bi,Pb)-2223/Ag tapes in 8.5% O-2 atmosphere. The tapes were sintered within 770-800 degrees C for 10 h and at 795 degrees C for 5-50 h. The measurements showed that I-c (77 K,SF) was increased by 12-19% after PA within 790-800 degrees C. It was found by means of XRD that the Pb-3(Bi0.5Sr2.5)Ca2CuOx (3321) phase appeared after PA, its amount decreasing with increasing PA temperature. There was an optimum 3321 content to achieve the maximum I-c. T-c was increased by PA, and then decreased with increasing temperature. The field dependent I-c and n value measurements performed at 4.2 K, 10 K, 30 K and 77 K suggested that PA improves grain connectivity and collective flux pinning. (c) 2006 Elsevier B.V. All rights reserved.