A Study on the Processing Variables of the BSCCO-2212 Bulk Superconductors

Bi-2212/SrSO
₄
bulk superconductors were fabricated using a casting process, and the effects of the powder mixing method, annealing temperature, and SrSO
₄
content on the texture, microstructure, and critical properties were evaluated. The Bi-2212 powders were mixed with SrSO
₄
either by hand-mixing (HM) or planetary ball milling (PBM), followed by melting at 1100degC-1200degC, solidification, and annealing. The rod produced by PBM had a more homogeneous microstructure and smaller grain size of SrSO
₄
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 810degC. 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 SrSO
₄
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 SrSO
₄
addition.