Theoretical estimate of critical transport current density in polycrystalline oxide superconductors

Abstract

Percolative critical transport current densities in polycrystalline high T c oxide superconductors with orientated and random textures are theoretically estimated at the liquid nitrogen temperature. The effect of depression of the current through grain boundaries recently found by Dimos et al. was taken into account in the estimation. The critical current density obtained in polycrystalline materials with orientated textures is of a comparable order of magnitude with the recent observation by Jin et al. and the result suggests a possibility of further improvement up to 10 9 A m −2 by increasing the pinning strength. As for randomly textured materials, the theoretical estimate of critical current density is much larger than values commonly observed. The depressing effect of the current by grain boundaries in randomly textured materials is deduced to be much more significant than that observed by Dimos et al.