Fabrication and characterization of microstructural evolution and properties of twisted Bi(Pb)-Sr-Ca-Cu-O superconductor tape

We fabricated 37 multi-filament Bi-2223 (BSCCO) superconductor tapes and evaluated the effect of twisting on the microstructural evolution such as grain size, grain alignment, and interface morphology, and on the resulting critical current. Twist pitches of the BSCCO tapes are in the range of 70 to 8 mm and uniformly deformed. It was observed that the grain size and the degree of texture decreased with decreasing pitch, probably due to the formation of the irregular interface between the Ag and the filaments. In addition, the critical current of the tapes decreased with decreasing pitch. For the tape having a twist pitch of 8 mm, approximately 50% of the critical current was maintained compared to that of the untwisted tape. The reduction of critical current may be related to the interface irregularity, smaller grain size, poorer texture and presence of cracks due to the induced strain during the twisting processing.