Reduction of AC losses in Bi2223 tapes with interfilamentary oxide barriers

Abstract

In order to suppress the interfilamentary coupling under AC external magnetic field, increasing the transverse resistivity by using Ag-alloy sheath with high resistivity as a matrix or introducing oxide layers as resistive barriers among the filaments should be necessary, together with the filament twisting. In this paper, we fabricated twisted (Bi,Pb) 2Sr 2Ca 2Cu 3O x (Bi2223) tapes with interfilamentary oxide barriers and evaluated the effect of barrier introduction on AC loss properties in a perpendicular transverse field. The conventional powder-in-tube method was used for tape fabrication. To avoid the side effect on Bi2223 phase formation, SrZrO 3 was selected for barrier materials. In addition, 20 wt% Bi2212 was mixed with SrZrO 3 to improve its ductility for cold working. Monocore Ag-sheathed rods were dip-coated by the oxide barriers with slurry before stacking with multifilamentary structures. By applying both the tight twisting with twist pitch below 10 mm and introducing interfilamentary barriers, the coupling frequency in a perpendicular field was increased above 100 Hz and perpendicular field losses were reduced from the analytical prediction for fully coupled filaments around power-grid frequency range.