Effect of calcination conditions on microstructures and J_c of YBCO films fabricated by TFA-MOD method

YBCO films were grown on LaAlO₃ substrates by a metal organic deposition using trifluoroacetates (TFA-MOD). In the TFA-MOD method, a starting solution is coated on a substrate firstly, and then the coated film is calcined to form precursor and finally the precursor film is crystallized to form superconducting YBCO film. In this study, the effects of calcination conditions such as temperature on the microstructures and J_c properties of the YBCO films were studied. In the calcination step, spin coating and calcination were repeated three times for obtaining thick film under the maximum temperatures of 400-500 °C. The prepared precursor films were crystallized at a constant condition. The J_c values of the films calcined at 500 °C after at 400 °C × 2 times, 400 °C × 3 times and 500 °C × 3 times were about 1.49 MA/cm², 2.52 MA/cm² and 1.47 MA/cm², respectively. J_c depended strongly on the calcination temperature. The cross-sectional TEM images showed that the YBCO film calcined at 400 °C × 3 times had less pores than the others. Optimization of the calcination temperature was important to suppress the formation of large precipitates in precursor film, resulting in the suppression of the large pores in the YBCO film.