Fabrication of YBCO coated conductor by TFA-MOD using the "211 process"

YBCO film was fabricated by the TFA-MOD method based on the "211 process" in which precursors of Y₂Ba₁Cu₁O_x (Y211) and Ba₃Cu₅O₈ powders, instead of Y-, Ba-, and Cu-based acetates, were dissolved in trifluoroacetic acid (TFA) in order to explore its possible application in coated conductors. We evaluated the effects of the humidity and firing temperature on the phase formation, texture formability, and critical temperature (T_c) and current (I_c) of the YBCO film. We successively synthesized pure YBCO films of which those fired in 12.1-20.0% humidified Ar gas showed the highest critical properties, viz. a T_c-zero of 88.6 K and I_c of 30 A/cm width. These improvements in the critical properties were attributed to the formation of pure YBCO phase, to the improved density and the large grain size. In addition, we observed that the I_c varied significantly with the firing temperature. The variation of the I_c with the firing temperature was correlated with the microstructural evolution.