Critical current in silver sheathed Bi-2223 tapes

Silver sheathed Bi-2223 tapes have been investigated by transport and magnetization measurements in the temperature range between 4.2 K and 77 K for magnetic fields up to 12 T. The superconducting current through the tape can be explained by assuming a network of platelike grains coupled by weak links. At high temperatures the critical current is governed by flux creep of pancake vortices within the grains. At temperatures below 40 K this intragrain critical current exceeds the intergrain Josephson current leading to a weak link limitation in the tape. In this picture the differences between critical transport and magnetization currents can be explained by a reduction of the geometrical length scale of current loops. An improvement of the weak link current density is observed in multifilamentary wires and tapes with AgCu sheath material.