TRANSPORT CRITICAL CURRENT DENSITY DISTRIBUTIONS IN Ag/Bi-2223 TAPES

摘要

IV characteristics have been studied for monocore Ag sheathed Bi-2223 tapes, fabricated from both sol-gel and mechanically-milled precursor powders. Results have been obtained with the c-axis of the sample both parallel and perpendicular to the applied field, together with the force-free orientation. The angular dependence of the critical current has also been measured. The IV characteristics have been analysed in terms of their n-value and second-differential. The spatial dependence of the critical current has been measured using a scanning Hall probe. The results suggest that the transport current follows a percolative path which is limited by current flow in the c-axis direction, and that most of the current flows in a thin layer of highly aligned Bi-2223 grains near to the Ag sheath. The limiting mechanism in the c-axis direction is thought to be weak-link grain boundaries.