The Effect of Growth Temperature on Coated Conductors Fabricated by the RCE-DR Process

We investigated the effect of the growth temperature on the microstructures and superconducting properties of GdBa₂Cu₃O_7-δ (GdBCO) coated conductors (CCs) deposited by the Reactive Co-Evaporation Deposition and Reaction process on the LaMnO₃-buffered IBAD MgO template. For the growth of GdBCO films with ~1.5μm thickness at the oxygen pressure of 150 mtorr, we employed three different growth temperatures of 840, 860, and 880 °C. By decreasing the growth temperature, the critical current densities Jc at 65 and 77 K were improved due to enhanced pinning properties, which are attributable to refined Gd₂O₃ particles trapped in the GdBCO matrix. Analyses by transmission electron microscopy revealed that the average particle size of Gd₂O₃ is 126.5 nm in the 840 °C sample, which is smaller than that of 171.4 nm in the 860 °C sample and 217.8 nm in the 880 °C sample. Interestingly, although (103)-misoriented GdBCO grains existed together with biaxially textured grains in the film grown at 840 °C, they exhibited higher J_c values in magnetic fields compared with other films composed of only biaxially textured grains, suggesting that the increase in J_c due to pinning by refined Gd₂O₃ particles surpasses the degradation of Jc by (103)-oriented grains present at the film surface.