Fluorine-free water-based sol–gel deposition of highly epitaxial YBa2Cu3O7−δfilms

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) YBa 2 Cu 3 O 7−δ (YBCO) films were dip coated on SrTiO 3 (STO) single-crystal substrates. After gelation at 60 °C, the amorphous gel was transformed to the desired crystalline superconducting phase. Sintering was conducted at 815 °C under a 200 ppm oxygen partial pressure, followed by a pure oxygen annealing at 400 °C. Highly textured (Δω = 0.2°, Δφ = 6.5°) YBCO films with a T c,onset of 92 K, a Δ 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.