Characterization of oxygen deficiency and trivalent zirconium in sol-gel derived zirconia films

Zirconia films were prepared on silica glass substrates from the precursor solution of zirconium oxychloride octahydrate and acetic acid. The films were baked at 450 degrees C. The existence of oxygen deficiency and Zr(III) in the sol-gel derived zirconia films was characterized by UV and ESR spectral studies. The films baked in air, as well as in oxygen atmospheres, exhibited different UV absorption behaviours. The electronic transition at 5.45 eV of the air-baked film was identified with oxygen deficiency by studies of the functional dependence of the optical absorption coefficient on photon energy. The fundamental electronic transition at 5.80 eV of the films baked in different atmospheres was also identified by the same technique. The non-stoichiometric formula of zirconia (ZrO1.63) was calculated from the relative change of the absorption coefficients (at 5.80 eV) of films of the same thickness 1818+/-20 Angstrom cured in different atmospheres. The size of zirconia particles was determined by transmission electron microscopy (TEM) and found to be below 150 Angstrom. Electron diffraction patterns suggested that the structure of the metastable zirconia was cubic.