DEFORMATION-INDUCED TEXTURE IN COLD-ROLLED AG SHEATHED BI(2223) TAPES

We have found that the Bi(2212) grains in unreacted Ag/Bi(2223) tapes at the end of the cold-rolling process show already a high degree of texture. X-ray diffraction analysis and current transport measurements at 77 K in magnetic fields up to 0.5 T have been performed before and after reaction on tapes with thicknesses in the range from 75 to 286 mu m (filament thicknesses between 30 and 115 mu m) The critical current density j(c) increases for smaller tape thicknesses, a maximum being found for a tape thickness of about 90 mu m, below which sausaging effects are observed. The mean misalignment angles of Bi(2223) grains in these tapes have been determined by angle-dependent transport critical current data at 77 K. We have found that the main reason for the enhancement of j, for thin tapes is due to the higher average texture of the Bi(2223) grains when compared to thick tapes. This is a direct consequence of the high degree of texture of Bi(2212) grains after the cold-rolling process, which has been observed here on 90 mu m thick tapes with j(c)(77 K, 0 T) reaching between 25 and 30 kA/cm(2).