Critical current density and pinning energy in Ag-clad BPSCCO tapes

A ''sandwich rolling'' process was developed to prevent the formation of sausaging and cracks in the longitudinal direction since the stress-strain state of the tape in ''sandwich'' rolling is the same as that of uniaxial pressed tape. Critical current densities of 3.2 x 10(4) A/cm(2) at 77 K and 2.7 x 10(5) A/cm(2) at 4.2 K and zero field Ag-sheathed Bi-based 2212 tapes have been achieved using a melt and atmosphere-controlled process. The comparison of pinning potential U-0(B) = U(T = 0, B) for Bi-2212 tape and Bi-2223 tapes consisting of different fractions of the 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 tapes is at least 1.3 times that for the best 2212 tape and epitaxial thin films, indicating that in BSCCO compounds, in addition to anisotropy, the specific pinning centres such as dislocations, introduced during processing, affect the flux motion at lower B.