Fabrication and characterisation of superconducting rings for fault current limiter application

Bi-2212 supercondcuting rings (380 mm in diameter) were processed in a rotating furnace in flowing oxygen using Ag foil as the substrate. The powder was heated to the partial melt state, cooled to 855 degrees C to develop superconducting phase, annealed in N-2 rich atmosphere, and finally cooled in N-2 from 700 degrees C. This process has been optimised to achieve smooth surface finish and uniform thickness in the rings. Microstructure studies suggest that the as-processed Bi-2212 rings are highly densified and consist of random oriented Bi-2212 grain bundles. The Bi-2212 rings show a high T-c onset of 96K and a typical J(c) of 1500 Acm(-2) with I-c of 2500 A.