Temperature and magnetic field dependence of critical currents in YBCO coated conductors with processing-induced variations in pinning properties

Several applications of high-temperature superconducting wire require high currents at intermediate magnetic fields B and over a range of orientations; however, such conditions are at present achievable only at low temperatures (similar to 30 K). The goal of this study is to determine the feasibility of higher operating temperatures for these applications by investigating temperature dependent, low- and high-field pinning properties of YBCO coated conductor samples. The YBCO films were grown on RABiTS templates by a PVD ex situ BaF2 process. Variations in pinning properties were induced by introducing excess yttrium (Y) in the precursor and controllably increasing the growth rate. The main result is a more uniform dependence of J(c) over all orientations of B, along with high irreversibility field B-irr and high critical current densities J(c). Results also show that for films with various pinning properties and processed under different conditions the self-field J(c) at 77 K is an effective indicator of performance in the temperatures and fields of interest.