The Influence of Pre-Existing Defects on the Bending Strain Behavior of Bi2Sr2Ca1Cu2Ox and (Bi,Pb)2Sr2Ca2Cu3Ox Ag-Sheathed Tapes

Abstract

The effect of pre-existing defects on the bend strain behavior in Bi2Sr2Ca,Cu2OX (Bi-2212) and (Bi,Pb)2Sr2Ca2Cu3OX (Bi-2223) Ag-sheathed tapes was studied. For Bi-2212 at 4.2 K, we found that the transport critical current (Ic) declined by only 1% at bending strains less than 0.15%. However, the magnetization critical current density was sensitive to small bending strains, as evidenced by a strain of ~ 0.08%, which reduced the magnetization by 25%. For pressed Bi-2223 tapes at 77 K, essentially no reduction in was observed for strains less than 0.1%. At strains greater than 0.2%, lc dropped to only 10% of its original value at a strain of ~0.4%. The magnetization of pressed Bi-2223 at 77 K responded similarly to that of Bi-2212 tapes. Using magneto-optical imaging, we observed that the strain tolerance of Bi-2212 and Bi-2223 is strongly dependent on the pre-existing defects found in the cores of the tapes.