Characteristics of high-J_c GdBCO coated conductors fabricated by the RCE-DR process

We report the characteristics of GdBa₂Cu₃O _7-δ (GdBCO) coated conductors (CCs) on LaMnO₃ (LMO)-buffered IBAD MgO template, produced by the Reactive Co-Evaporation Deposition & Reaction (RCE-DR) process. The transport and magnetic critical current density (J_c) values of GdBCO CC samples were 3.7 and 2.92 MA/cm² at 77 K in self-field for B//c, respectively. Analyses by transmission electron microscopy revealed that a large amount of elongated round Gd₂O₃ particles with 70-150 nm size and a small amount of the Cu-O phase were trapped in the GdBCO matrix, and a thick layer of the Cu-O phase was also found on the top surface of the GdBCO film, suggesting that the GdBCO film must be grown by the peritectic recombination reaction between Gd₂O₃ and a liquid phase. While both the GdBCO film and some Gd₂O₃ particles grown on the LMO-buffer layer were biaxially textured, the Gd₂O₃ particles fully trapped in the GdBCO matrix were randomly oriented. The GdBCO film by RCE-DR possessed slightly degraded value of exponent α ∼ 0.84 in the power-law relationship J_c ∼ H^-a and rather large anisotropy in field-orientation dependence of J_c, J_c(θ), and thus refinement of Gd₂O₃ particles may be required for stronger flux pinning.