Filament decoupling and magnetization loss of multifilamentary Bi2223 superconducting tapes

Several types of multifilamentary Bi2223 superconducting tape were fabricated to study the filament decoupling and its effect on the magnetization loss reduction. First, twisted and untwisted multifilamentary Bi2223 tapes with pure silver matrix were prepared. The spacing between filaments was increased to ensure the suppression of the inter-filament bridging. Therefore, the engineering current density decreased, while the critical current density was kept at 150 A/mm/sup 2/. Measured magnetization loss of the tapes indicates that filaments are decoupled by twist in the parallel magnetic field, and the hysteresis loss is reduced. Second, the inter-filament resistive barriers were introduced. Several materials were tested as the barrier material to study their compatibility with the formation of Bi2223 phase during the fabrication process. The tapes with resistive barrier were fabricated successfully with a couple of meters of piece-length. DC magnetization of the fabricated tapes was measured by a SQUID magnetometer. The magnetization-temperature curves indicate that Bi2201, not superconducting at 77 K, and the Al/sub 2/O/sub 3/ do not affect the formation of Bi2223 superconducting phase. The transverse resistivity of a Bi2201-barrier tape, estimated from the measured coupling time constant, is 4.7/spl times/10/sup -8/ /spl Omega/m. Results of AC magnetization loss measurement indicate that the filaments can be decoupled by the Bi2201 barrier.