Voltage vs. current characteristics of Bi-2212/Ag tapes and coils

Recently: we developed as: Pre-Annealing and Intermediate Rolling (PAIR) process which significantly increased J(c) values of Br-2212/Ag tapes. In this paper, we evaluate E-J characteristics of PAIR-processed and non-PAIR-processed Bi-2212/Ag tapes. Slope of the log E-log J curve (n-value) of short tapes was much enhanced by the PAIR process. Comparison of E-J curves measured by the resistive method and magnetic method suggests that this improvement is due to the improvement of the microstructure rather than to the improvement of flux pinning characteristics. n-Values of an XO-m-long PAIR-processed tape were also larger than those of a non-PAIR-processed tape. However, the n-values of 80-m-long tape were smaller than those of the short tape, although the PAIR process was applied. (C) 2000 Elsevier Science B.V. All rights reserved.