Electromagnetic connectivity and microstructure in YBa₂Cu₃O_7-δ films on rolling-assisted biaxially-textured substrates

Biaxially-textured YBa₂Cu₃O_7-δ (YBCO) coated conductors are a central thrust of current efforts to fabricate high-critical-current-density (J_c) wire for large-scale applications of high-T_c superconductivity. Encouragingly high J_c values are obtained in laboratory-length samples. However, magneto-optic imaging indicates that the supercurrent path is percolative even in the best materials. Thus, it seems clear that the full potential current carrying capability of these composites has not been reached. This paper describes coupled magneto-optic imaging and microstructural studies of RABiTS^TM type coated conductors that indicate (1) the important roles of other microstructural features in addition to grain boundaries and (2) the need to explore the roles of the oxide buffer layer microstructure in optimizing the composite.