Preparation of epitaxial YBa2Cu3O7−y films on CeO2-buffered yttria-stabilized zirconia substrates by fluorine-free metalorganic deposition

Epitaxial YBa2Cu3O7−y (YBCO) films of 120–550 nm thickness have been prepared by fluorine-free metalorganic deposition using a metal acetylacetonate-based coating solution on yttria-stabilized zirconia (YSZ) substrates with an evaporated CeO2 buffer layer. The YBCO films were highly (0 0 1)-oriented by X-ray diffraction θ–2θ scanning and ϕ scanning. The YBCO films 120–400 nm in thickness demonstrated high critical current densities (Jc) with an average in excess of 3 MA/cm2 at 77 K using an inductive method. In particular, a 210-nm-thick film showed a Jc of 4.5 MA/cm2. These excellent properties are attributed to the high crystallinity, small in-plane fluctuation due to high epitaxy and to the microstructure free from grain boundaries in the YBCO films. Further increase of film thickness increased the fraction of irregularities, i.e., precipitates and micropores, in the film surfaces, resulting in lower Jc values.