Grain and grain-boundary critical currents in coated conductors with noncorrelating YBa_2Cu_3O_7 and substrate grain-boundary networks

摘要

The superconducting grain-boundary (GB) network of coated conductors (CCs) is usually assumed to be a replica of the substrate network. In this letter, we analyze IBAD and RABITS CCs, where such replica either do or do not exist. We have analyzed the effect of GB overgrowth on the critical currents by quantifying the average superconducting grain size and determining the intragrain and grain-boundary critical current densities, J_c~G and J_c~(GB). We have employed a recently developed inductive methodology enabling the simultaneous determination of these three parameters. We show that the percolative J_c~(GB) may be reduced by 50% if the GB networks do not correlate, while J_c~G and the grain pinning properties appear unaffected.