Progress in Reducing AC Losses of Bi2223 Tapes with Interfilamentary Resistive Barriers

This paper presents our recent progress for the development of low-AC loss Bi2223 tapes with interfilamentary oxide barriers. For the compatibility with Bi2223 phase formation during sintering, SrZrO₃ was selected as barrier materials. Moreover, small amount of Bi2212 was mixed with SrZrO₃ to improve its ductility for cold working. Although some breakages of barrier layers still existed, the effective transverse resistivity was approximately 10 times higher than a tape with pure Ag matrix. By controlling barrier thickness, reducing a tape width below 3 mm and twisting the filaments with its length below 5 mm , coupling frequency f_c attained to 260 Hz in an AC perpendicular transverse field. Critical current densities J_c of our twisted barrier tapes were ranged in 12-15 kA/cm² at 77 K and self-field, which was 25-30 % lower than non-twisted one (=18 kA/cm²). In our knowledge, this is the first report to achieve both J_c >; 12 kA/cm² and f_c 250 Hz simultaneously in a single Bi2223 tapes. Our barrier tapes showed 60-70% lower perpendicular field losses than a conventional 4 mm-width tape with fully coupled filaments at 50 mT and 50 Hz. These results are promising for remarkable improvement in AC performance for Bi2223 tapes in future.