Fluorine-free water-based sol-gel deposition of highly epitaxial YBa2Cu3O7-δ films

In this work a fluorine-free sol-gel method based on low-cost materials and water as primary solvent is developed, resulting in a sustainable superconducting film. Using a 0.6 M 'AWAT' precursor (M-acetates, water, acetic acid and tri-ethanolamine, patent pending) YBa2Cu3O7-delta (YBCO) films were dip coated on SrTiO3 (STO) single-crystal substrates. After gelation at 60 degrees C, the amorphous gel was transformed to the desired crystalline superconducting phase. Sintering was conducted at 815 degrees C under a 200 ppm oxygen partial pressure, followed by a pure oxygen annealing at 400 degrees C. Highly textured (Delta omega = 0.2 degrees, Delta phi = 6.5 degrees) YBCO films with a T-c,T- onset of 92 K, a Delta T-c of 5 K, a J(c) of 0.55 MA cm(-2) and an I-c of 25 A cm(-1) width at 77.3 K and self-field were achieved. Experimental results on film synthesis, morphology, microstructure and superconducting properties are presented.