IRREVERSIBILITY BEHAVIOR OF DIFFERENT TYPES OF BI-(PB)-SR-CA-CU-O SUPERCONDUCTORS

Comparative studies on Bi-2212 single crystal, Ag/Bi-2212 tape and Ag/ Bi-2223 tape have been carried out using a.c. susceptibility measureme nts. The irreversibility line for the Ag/Bi-2223 tape is positioned at higher temperatures than that for the 2212 tape which is in turn posi tioned at higher temperatures than that for the 2212 crystals. A compa rison between multifilamentary Ag/Bi-2223 tapes shows that the positio n of the irreversibility line shifts from low temperatures to high tem peratures in the sequence of hot-pressed, rolled and cold pressed tape s. These results indicate that the defects induced by mechanical defor mation act as pinning centres in these tapes, responsible for the impr ovement in flux pinning. (C) 1997 Elsevier Science B.V.