Epitaxial growth of biaxially aligned Y-Ba-Cu-O superconductors by spray pyrolysis on textured Ag ribbons and single crystal substrates

The deposition of Y-123 films by spray pyrolysis at room pressure on textured Ag ribbons was studied as an alternative to the high vacuum coated tapes techniques. It is shown that an epitaxial growth, at a rate of 0.35 μm/min, is obtained on rolled and annealed {110}⟨011⟩ textured Ag ribbons, without buffer layers. Processing parameters are optimized in order to get biaxially aligned Y-123 films with a thickness of a few micrometers. A nitrate solution of Y, Ba and Cu was sprayed on the substrate heated at 850°C-900°C. The films were then annealed in air in the same temperature range and then oxygen loaded in flowing oxygen. By a careful control of the nitrate stoichiometry in the aqueous initial solution, phase pure Y-123 films were deposited on (110) oriented Ag single crystals, {110}⟨011⟩ Ag textured tapes and (100) SrTiO₃ substrates. X-ray investigations show a high degree of c-axis alignment. A biaxial orientation is found from X-ray pole figures and φ-scans. FWHM values as small as 1°, 4° and 11° are measured on SrTiO ₃, (110) Ag single crystal and {110}⟨011⟩ Ag textured ribbons, respectively. The critical temperature was 90 K