Fabrication of YBCO coated conductor by TFA-MOD method in route of dissolving Y211 and Ba₃Cu₅O₈ powders in TFA

We fabricated YBCO coated conductors using a new TFA-MOD method and evaluated the phase formation, texture evolution, and critical properties as a function of the firing temperature and oxygen heat treatment time, in order to explore its possible application in CCs fabrication. In the fabrication process, Y₂Ba₁Cu₁O_x and Ba ₃Cu₅O₈ powders were used as precursors, instead of Y-, Ba- and Cu-based acetate or organics, and dissolved in trifluoroacetic acid followed by firing and oxygen heat treatment. We observed that for the films fired at 725 °C, BaF₂ and other second phases formed and T_c was measured to be 66.5 K. In contrast, when the film was fired at 775 °C, strong and sharp (0 0 l) diffraction peaks of YBCO were observed, without the formation of the BaF₂ phase. In addition, X-ray pole-figure analysis indicated that a strong biaxial texture was developed and the full-width at half-maximums of in-plane and out-of-plane textures were 4.38° and 4.26°, respectively. The critical temperature and current were also increased to 85.3 K and 35.8 A/cm-width, respectively, at 77 K when the oxygen heat treatment time was increased to 20 h. Microstructure observation indicated that a crack-free surface was obtained and that there was no a-axis grain growth.