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-sheat hed 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 fra ctions of the 2212 phase as well as Bi-2212 and Bi-2223 thin films sho ws that, for the same fields, the U-0 for good quality 2223 tapes is a t least 1.3 times that for the best 2212 tape and epitaxial thin films , indicating that in BSCCO compounds, in addition to anisotropy, the s pecific pinning centres such as dislocations, introduced during proces sing, affect the flux motion at lower B.