A study on the processing variables of the BSCCO-2212 bulk superconductors

Bi -2212/SrSO₄ bulk superconductors were fabricated using a casting process, and the effects of the powder mixing method, annealing temperature, and SrSO₄ content on the texture, microstructure, and critical properties were evaluated. The Bi-2212 powders were mixed with SrSO₄ either by hand-mixing (HM) or planetary ball milling (PBM), followed by melting at 1100°C-1200°C, solidification, and annealing. The rod produced by PBM had a more homogeneous microstructure and smaller grain size of SrSO₄ and minor phases, resulting in increased I_c, than the rod made by HM. The I_c of the rod was also dependent on the annealing temperature with the highest I_c of 200 A being obtained at an annealing temperature of 810°C. This was attributed to the moderate density and 2212 texture as well as the smaller and less minor phase than that observed at higher temperature. In addition, the optimum SrSO₄ content was found to be 6 wt.% for an increased I_c. SEM, EPMA, and DTA analyses indicated that the differences in microstructural evolution caused the variations of the I_c with the powder mixing method, annealing temperature, and SrSO₄ addition.