The effect of post-annealing on the critical current recovery of bending-deformed (Bi,Pb)-2223/Ag tapes

(Bi,Pb)-2223/Ag tape fabricated by PIT methods is a promising candidate for electrical power application. In these applications, the tape often undergoes a winding process, which leads to the degradation of the critical current. In this paper, we report the effect of post-annealing on the critical current (I-c) recovery of bent-deformed (Bi,Pb)-2223/Ag multi-filamentary tapes. The tapes were bent at room temperature with different curvatures, then straightened and post-annealed with different processing parameters, including post-annealing temperature, dwelling time and oxygen partial pressure. The experiment results show that rather high I-c value could be obtained by post-annealing even for the tapes whose bending strain was 0.8%. SEM observation shows that the decreasing in I-c value is caused by the formation and propagation of transverse micro-cracks in the (Bi,Pb)-2223 filaments and the effect of post-annealing could be related to the healing of micro-cracks caused by bending strain as well as the improving of grain connectivity. (C) 2007 Published by Elsevier B.V.