Study on reaction mechanism of YBa2Cu3O7–x; film by TFA-MOD process

This paper systematically investigates the intermediate phases of YBa2Cu3O7−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 YBa2Cu3O6.5 at about 725°C. The influence of water vapour pressure on the YBa2Cu3O7−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 Jc of 3.8 MA/cm2, which was attributed to the formation of a purer YBCO phase and stronger biaxial texture. (condensed matter: electronic structure, electrical, magnetic, and optical properties)