Optimization of fluorine content in TFA-MOD precursor solutions for YBCO film growth

Several low fluorine solutions containing different contents of fluorine were prepared by a chemical process. The fluorine contents in these solutions with respect to the conventional all-trifluoroacetate solution were calculated as 0%, 7.7%, 15.4%, 23.1%, 30.8%, 38.5% and 53.8%. YBa2Cu3O7−x (YBCO) films were deposited on LaAlO3 and CeO2/MgO/Al2O3/Hastelloy substrates using these low fluorine solutions. The phase formation, texture and microstructure of the YBCO films were characterized by x-ray diffraction and scanning electron microscopy. The decomposition mechanism of the low fluorine solution was also discussed. The results indicate that the ratio of F/Ba and the carbon content in decomposed powders could be controlled by adjusting the fluorine content in the precursor solutions. Fluorine had a great influence on the phase transformation, nucleation and growth of YBCO film during the crystallization process. The optimization of fluorine content was in the range of 15.4%–23.1%, which contributed to the good texture, homogeneous microstructure and high J c value of the YBCO crystallized films.