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 4.2K and 7 7K for magnetic fields up to 12T, The superconducting current through the tape can be explained by assuming a network of platelike grains co upled by weak links, At high temperatures the critical current is gove rned by flux creep of pancake vortices within the grains. At temperatu res below 40K this intragrain critical current exceeds the intergrain Josephson current leading to a weak link limitation in the tape, In th is picture the differences between critical transport and magnetizatio n currents can be explained by a reduction of the geometrical length s cale of current loops, An improvement of the weak link current density is observed in multifilamentary wires and tapes with AgCu sheath mate rial.