High-T_c superconducting joints for Ag-clad Bi-2223 tapes

A high-T_c superconducting tape joint between two Ag-clad Bi-2223 tapes has been fabricated and characterized. Two pre-sintered tapes with one side of the silver striped were lapped and then wrapped by a silver foil. The complex was uniaxially pressed and followed by appropriate sintering to form a high-T_c superconducting tape joint. Transport critical current through the joint (I_cj) was determined at liquid nitrogen temperature. It was found that the ratio of critical currents through the joint to that of the tape, I_cj/I_c, depended on the uniaxial pressure and the sintering conduction. For a test sample, I_cj/I_c reached 99%. Persistent current loops formed by Bi-2223 tapes have also been fabricated and tested. Joint resistance of a loop was determined to be ∼ 4 × 10^-13 Ω after the initial decay time of 2 minutes.