Study on reaction mechanism of YBa₂Cu₃O_7-x film by TFA-MOD process

This paper systematically investigates the intermediate phases of YBa₂Cu₃O_7-x (YBCO) film prepared by metalorganic deposition method using trifluoroacetates (TFA-MOD). According to x-ray diffraction and Raman analyses, the precursor film decomposed in a mixture of BaF₂, Y₂O₃ and CuO after the pyrolysis process. Then these intermediate phases converted into tetragonal YBa₂Cu₃O_6.5 at about 725 °C. The influence of water vapour pressure on the YBa₂Cu₃O_7-x film growth on LaAlO₃ single-crystal substrates was also studied. The films prepared at low water vapour pressures (40--140 hPa) showed poor electrical performance due to the a-axis grain structure and impurity phases. However, the films prepared at 190 hPa exhibited the highest critical temperature of 90 K and the highest J_c of 3.8 MA/cm², which was attributed to the formation of a purer YBCO phase and stronger biaxial texture.