Microstructure analysis of GdBa₂Cu₃O_7-δ coated conductors by the RCE-DR process

We report the microstructural features 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. Analysis results by X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that a lot of elongated round second phase particles of 70-150nm size within the GdBCO matrix were the Gd₂O₃ phase, a small amount of Cu-O phase were also trapped in the GdBCO matrix, and a thick layer of Cu-excessive Ba-Cu-O phase was found on the top surface of the GdBCO film, suggesting that the GdBCO film might be grown from Gd₂O₃ and liquid phase by a peritectic recombination. 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 Gd₂O₃ particles located at the interface between the GdBCO and LMO buffer layer exhibited the following crystallographic orientation relationship: LMO [010] // GdBCO [010] // Gd₂O₃ [110]; LMO [001] // GdBCO [001] // Gd₂O₃ [001].