Optimum Composition in 10% Zr-added GdYBCO Coated Conductor for Enhanced Flux Pinning at 30 K

(Gd, Y)Ba₂Cu₃O_x superconducting films with 10% Zr addition were grown by metal organic chemical vapor deposition (MOCVD) on hastelloy substrate tapes with IBAD-MgO based buffer. The critical current properties in an applied magnetic field up to 3 T were studied at temperatures of 30 K and 77 K, while systematically varying the film composition specified by atomic ratios of RE/Ba and Cu/Ba. The in-magnetic-field critical currents at 30K were found to be more sensitive to the variation in film composition than those at 77 K. At 77 K and zero applied magnetic field, the optimum film composition for high critical current density was found to be around (RE/Ba = 0.63, Cu/Ba = 1.62). At 30 K and 3 T, however, the highest critical current density was obtained with the film composition of (RE/Ba = 0.58, Cu/Ba = 1.5). Therefore, different composition recipes should be used for applications operating at different temperatures.