Fabrication of high-quality epitaxial YBCO films prepared by fluorine-free MOD

High-quality epitaxial YBa₂ Cu₃ O_7-δ (YBCO) films were successfully fabricated on LaAIO₃ (LAO) (001) substrates by fluorine-free metal-organic deposition (MOD). YBCO powder was dissolved into a fluorine-free source to prepare the coating solution. The solution was dip-coated on LAO, dried at 80 ° for 10 min, pyrolized at the temperature up to 400 ° in humid O₂ atmosphere, subsequently fired to produce YBCO in an oxygen partial pressure of 300 ppm, and finally oxygenated in a pure O₂ atmosphere at 450 ° for 1 h. While, in addition to -axis oriented grains, the formation of randomly oriented polycrystalline grains was unavoidable when as-pyrolized films were simply fired at 825 ° for 2 h, high-quality epitaxial YBCO films with only a small amount of -axis oriented grains were obtainable when as-pyrolized films were heated up to 850 ° at first and then cooled down to 825 ° and held for 2 h at the firing stage. Although our best YBCO film had a T_c,zero value of 87.5 K and J_c value of 0.47 MA/cm² at 77 K in a self-field at the present stage, this fluorine-free MOD is a promising alternative to conventional TFA-MOD since further improvement in J_c is possible through the processing optimization.