Effects of firing temperature and film thickness on the critical properties of YBCO film by the "211 process"

We fabricated by metal organic deposition (MOD) using trifluoroacetic acid (TFA) via the "211 process", and then evaluated the phase formation, texture evolution, and critical properties as a function of the firing temperature and film thickness. In the fabrication process, Y₂Ba ₁Cu₁O_x and Ba₃Cu₅O ₈ powders were used as precursors instead of Y-, Ba- and Cu-based acetates. The films were fired in the temperature range of 750°C -800°C and the film thickness of films was controlled by repeating the number of coating cycles. The microstructure varied significantly with the firing temperature. The grains size increased, the film became denser, and the degree of the texture and phase purity varied with increasing firing temperature. The films fired at 775°C after calcining at 400 showed the highest critical current (I_c) of 18 A/cm-width, which corresponds to a critical current density (J_c) of 0.9 MA/cm². For multi-coated films, the I_c increased from 18 in the singly coated film to 100 A/cm-width with the triply coated film. In contrast, the corresponding J _c were in the range of 0.9-1.2 MA/cm². Both I_c and J_c values decreased as the coating number repeated further as a result of the degraded microstructure.