We describe the preparation and characterization of zirconia (ZrO2) thin films via sol-gel route by spin-coating method. By utilizing alkoxides Zr[O(CH2)(3)CH3](4) in the presence of ethanol (EtOH), nitric acid and acetylacetone as a chelating agent, a stable sol of ZrO2 was obtained. Smooth surface morphology with nano-cracks was exhibited for all ZrO2 thin films being fabricated. The film thickness varied from 39 to 206 nm depending on the molar ratio of EtOH during the sol preparation and also annealing temperature applied. All ZrO2 films possess high optical transmittance. Refractive index of the thin film was ranging from 1.6 to 2.4 depending on molar ratio of EtOH and annealing temperature. Tetragonal phase of ZrO2 was formed after annealed at 400 degrees C. Crystallinity of ZrO2 was enhanced by increasing molar ratio of EtOH. Crystallite size of tetragonal ZrO2 was ranged from 3.0 to 9.9 nm. A hot-water treatment reduced the film thickness and further improved crystallinity of the sol-gel derived oxide. (c) 2012 Elsevier B.V. All rights reserved.