FABRICATION AND CHARACTERIZATION 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. Th e powder was heated to the partial melt state, cooled to 855 degrees C to develop superconducting phase, annealed in N-2 rich atmosphere, an d finally cooled in N-2 from 700 degrees C. This process has been opti mised to achieve smooth surface finish and uniform thickness in the ri ngs. Microstructure studies suggest that the as-processed Bi-2212 ring s are highly densified and consist of random oriented Bi-2212 grain bu ndles. 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.