Development of Low-Loss (Bi,Pb)-2223 Tapes with Interfilamentary Resistive Barriers

Abstract

This paper presents our recent activities for the development of low-loss (Bi,Pb)-2223 tapes with interfilamentary resistive barriers. To suppress the side effect on the phase formation in the filaments during sintering, SrZrO3 were selected as barrier materials. Moreover, small amount of Bi-2212 was mixed with SrZrO3 to improve their ductility for cold working. For non-twisted barrier tapes, transport critical current densities Jc at 77 K and self-field were ranged between 18 and 21 kA/cm2 and its uniformity within 4% along a 1 m length. By combining the barrier introduction, reducing the tape width (< 3 mm) and twisting the filaments tightly, coupling frequency fc exceeded 250 Hz even in an AC perpendicular field at 77 K. Transport Jc of the barrier tapes with tightly twisted filaments were in the range of 1214 kA/cm2 at 77 K and self-field. In our knowledge, this is the first result to achieve both Jc > 12 kA/cm2 and fc > 250 Hz simultaneously in an isolated (Bi,Pb)-2223 tape. At 50 mT and 50 Hz, our twisted barrier tapes showed 60-70% lower perpendicular field losses than a conventional 4 mm-width tape with fully coupled filaments.