Through-thickness superconducting and normal-state transport properties revealed by thinning of thick film ex situ YBa2Cu3O7−x coated conductors

A rapid decrease in the critical current density (Jc) of YBa2Cu3O7−x (YBCO) films with increasing film thickness has been observed for multiple YBCO growth processes. While such behavior is predicted from two-dimensional collective pinning models under certain assumptions, empirical observations of the thickness dependence of Jc are believed to be largely processing dependent at present. To investigate this behavior in ex situ YBCO films, 2.0- and 2.9-μm-thick YBCO films on ion beam assisted deposition-yttria stabilized zirconia substrates were thinned and repeatedly measured for ρ(T) and Jc(H). The 2.9 μm film exhibited a constant Jc[77 K, self-field (SF)] through thickness of ∼1 MA/cm2 while the 2.0 μm film exhibited an increase in Jc(77 K, SF) as it was thinned. Neither film offered evidence of significant dead layers, suggesting that further increases in critical current can be obtained by growing thicker YBCO layers.