Development of high-T_c superconducting Bi-2223 tape joints

High-T_c superconducting joints between Ag-clad Bi-2223 tapes have been developed for persistent current applications. Two presintered tapes with one side of the silver stripped were lapped and then wrapped by a silver foil. The complex was uniaxially pressed followed by appropriate sintering to form a high-T_c superconducting tape joint. 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. At liquid-nitrogen temperature 77 K, Icj/I_c = 99% has been achieved. 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 between the decay time of 120 and 3600 sec.