Fabrication of TFA-MOD YBCO films using the y₂Ba ₁Cu₁O_x and Ba₃Cu₅O ₈ powders

We fabricated YBCO film using a TFA-MOD method and evaluated the phase formation, texture evolution, and critical properties as a function of the firing temperatures. In order to enhance the reaction kinetics and to control the formation of the second phases, Y₂Ba₁Cu ₁O_x and Ba₃Cu₅O₈ powders were used as precursors (the so called "211 process"), instead of Y-, Ba-, and Cu-based acetate, and dissolved in trifluoroacetic acid (TFA). The films were calcined at 460°C and then fired at 750°C-800°C in a 12.1% humidified Ar-O₂ atmosphere. We found that the microstructure varied significantly with the firing temperature; the grain grew further and the film became denser as the firing temperature increased. The textures of all of the films were similar and mainly biaxial. On the other hand, the intensity of the major and minor texture components differed from each other. For the film fired at 775°C, the critical current was obtained to be 39 A/cm-width (corresponding critical current density is 2.0 MA/cm²), which was probably attributed to such factors as the enhanced phase purity and out-of-plane texture, the moderate film density and grain size, and crack-free surface.