Effect of fluorine on the intermediate phase evolution for GdBCO film growth

Four simple low fluorine solutions with different fluorine contents were developed to grow GdBa2Cu3Oy (GdBCO) superconducting films, and the total fluorine contents were adjusted from 0 to 19.2% in comparison with the standard trifluoroacetate acid (TFA) solution. The thermal decomposition and crystallization of low fluorine solutions were investigated to understand the role of fluorine on the intermediate phase evolution for the growth of GdBCO film. With increasing fluorine content, the decomposition reaction region became narrow. Fluorine could catalyze the reaction and make pyrolysis abruptly. Furthermore, the evolution of intermediate phase was great affected by the change of fluorine content, which might lead to the change of microstructure and performance of GdBCO film. At the case of 11.5%, the intermediate phases contained BaF2, BGF, Gd2O3 and copper oxide without BaCO3 residue. And GdBCO film with the epitaxial growth, uniform microstructure and Jc of 1.58 MA/cm2 could be acquired. The optimization of intermediate phase derived from precursor solution would be helpful for high performance of GdBCO films.