Study for AC Loss Reduction in Bi2223 Tapes by Introducing Oxide Barriers

This paper presents our recent activities for the development of low-loss Bi2223 tapes with interfilamentary oxide barriers. In order to suppress the side effect on Bi2223 phase formation during sintering process, SrZrO(3) was selected as barrier materials. Moreover, small amount of Bi2212 was mixed with SrZrO(3) to improve their ductility for cold working. By controlling coating thickness of oxide barriers before stacking, reducing a tape width below 3 mm and careful twisting of the filaments with its length below 5 mm, coupling frequency f (c) exceeded 250 Hz even in an AC perpendicular magnetic field. Critical current densities J (c) of tightly twisted barrier tapes were ranged in 12-14 kA/cm(2) at 77 K and self-field, which was 25% lower than the nontwisted one (=18 kA/cm(2)). To our knowledge, this is the first result to achieve both J (c)> 12 kA/cm(2) and f (c)> 250 Hz simultaneously for Bi2223 tapes in an isolated state. These twisted 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.