Texture analysis in the thermo-mechanical processing of Bi-2223 tapes

We have investigated c-axis texture development in Bi-2223/Ag tapes made by American Superconductor Corp. at various points in a thermo-mechanical process using three methods: XRD rocking curves, the anisotropic field dependence of critical current density J_c, and the magnetization anisotropy. We assess the limitations of each technique, and uncover trends in texture development during the processing sequence. For the rocking curve measurement this involved establishing the uncertainty in measurement of the distribution width of misorientation angles, the variability in misalignment in successive adjacent sections of tape, and the impact of surface grinding on the measurement, while for the magnetic technique we have investigated methods to reduce the contribution from global transport currents, and also the effect of field sweep-rate on the derived texture. For a two-step heat treatment sequence, we find a large rise in texture after the first heating step, a drop after intermediate rolling, and almost complete recovery during the final heating step. The transport data does not show a strong correlation between texture and J_c across a variety of samples (J_c of 30 k-50 kA/cm², 77 K & self-field), within a limited range of texture.