EFFECT ON CRITICAL-CURRENT DENSITY AND IRREVERSIBILITY BEHAVIOR OF MECHANICAL DEFORMATION OF BI-(PB)-SR-CA-CU-O SUPERCONDUCTING TAPES

Comparative studies on the Ag-clad 27-filamentary Bi-2223 tapes deform ed under different conditions have been carried out using sc susceptib ility and critical current measurements. Hot pressing improves the gra in alignment and grain connectivity, resulting in a noticeable improve ment in the critical current density in the low field region. However, the irreversibility line for the cold pressed Ag/Bi-2223 tape is posi tioned at higher temperatures than that for the rolled tape which is i n turn positioned at higher temperatures than that for the hot-pressed tape. These results indicate that the hot deformation is only benefic ial to the improvement of weak links whereas the cold deformation indu ces more defects which act as pinning centres in these tapes, responsi ble for the improvement in flux pinning.