Characterization of Ag-Sheathed Bi2223 Tapes with Interfilamentary Oxide Barriers AC Loss Reduction under AC Perpendicular Transverse Magnetic Field

Abstract

Synopsis:Low AC loss Ag-sheathed Bi2223 tapes with oxide barriers among the twisted filaments were successfully fabricated using the powder-in-tube method. SrZrO 3 was selected as the barrier material for its compatibility with Bi2223 oxide.Moreover, a small amount of Bi2212 was mixed with SrZrO 3 to improve its ductility for cold working. By controlling barrier thickness and reducing the final tape width down to 2.7 mm, transport critical current densities J c at 77 K and self-field attained 17-23 kA/cm 2 for twisted barrier tapes with twist lengths L t between 4 and 9 mm. For barrier tape with the shortest L t = 4 mm, a coupling frequency f c , which is related to inverse of coupling time constant W c , of 270 Hz was attained in an AC transverse field perpendicular to a broader face of the tape. To our best knowledge, f c = 270 Hz under a perpendicular field is the highest ever reported value for Bi2223 tapes with self-field J c > 15 kA/cm 2 at 77 K. According to these achievements, perpendicular field losses around 50 Hz for barrier tape were 70-80% lower than those for conventional 4 mm-width tape with fully coupled filaments.