SANDWICH ROLLING, J(C), AND PINNING ENERGY IN AG-SHEATHED BPSCCO SUPERCONDUCTING TAPES

A ''sandwich rolling'' process was developed to prevent the formation of sausaging and cracks in the longitudinal direction. The stress-stra in state of the tape in ''sandwich'' rolling is the same as that of un iaxial pressed tape because the deformation of steel sheets is negligi ble in comparison to that of Ag-clad tape. Critical current densities of 3.2 x 10(4) A/cm(2) at 77K and 2.7 x 10(5) A/cm(2) at 4.2K and zero field Ag-sheathed Pi-based 2212 tapes have been achieved using a melt and atmosphere-controlled process. The comparison of pinning potentia l U-0(B) = U(T-0, B) for Bi-2212 tape and Bi-2223 tapes consisting of a different fraction of 2212 phase as well as Bi-2212 and Bi-2223 thin films shows that for the same fields, the U-0 for good quality 2223 t apes is at least 1.3 times that for the best 2212 tape and epitaxial t hin films after taking into account the difference of the T-c between 2223 tape and 2212 tape, indicating that in BSCCO compounds, in additi on to anisotropy, the specific pinning centers such as dislocations, i ntroduced during processing, affect the flux motion at lower B.