Deformation state effects on the Jc of BSCCO tapes

Abstract

Developing long-length, high- J c superconducting tapes has been a major world-wide effort in recent years because of their potential applications in power-transmission lines, motors, and other devices. The superconducting tape is usually produced by co-deforming a ductile silver sheath containing a superconducting oxide. Since the conventional thermomechanical process has failed to yield sufficient J c values for most liquid-nitrogen temperature applications, new approaches are needed to improve the criticalcurrent density, J c. This study investigated the feasibility of improving J c by increasing the shear and compressive stresses in the silver-sheathed Bi 2Sr 2Ca 2Cu 3O 10 + x (BSCCO-2223) tapes during the rolling. To investigate the effects on the J c of the stress state during rolling, specific stress states were imposed by rolling the BSCCO tapes embedded at different locations within thick steel blocks. Pure compression loading was achieved in the center plane of the blocks, while a combined compression-shear loading state was produced away from the center plane. Higher compressive hydrostatic stress at the tape edge was obtained by confining the tape width. Tapes deformed with a shear stress component exhibited higher J c values than tapes subjected to pure compression. In addition, the compressive hydrostatic stress reduced the porosity in the oxide near the tape edge and, as a consequence, increased the J c value.