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

Several applications of high-temperature super-conducting 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 (∼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.