Nanocrystalline zirconia thin films have been deposited on borosilicate glass substrates at ambient temperature by direct current (dc) magnetron sputtering. The present study demonstrates the possibility of growing zirconium oxide films in 100% pure oxygen dc plasma. Films of thickness of the order of 500 nm have been grown using a metallic Zr target in pure oxygen plasma. Interestingly, the presence of high temperature polymorphs of ZrO(2) is observed in films deposited with 40, 60 and 80% oxygen in the sputtering gas, while only the monoclinic phase is observed at lower and higher oxygen percentages. The refractive index in this range of oxygen percentages peaks at 1.85 in the dispersion free region. The crystallite size in the films varies between 11-25 nm, as calculated from X-ray diffraction patterns and is dependent on oxygen percentage in the sputtering gas. The grain sizes observed in atomic force microscope images are in the range 38 to 45 nm. The dielectric constants of the films, measured at microwave frequencies [8-12 GHz] ranged between 13-19.2. (C) 2008 Elsevier B.V. All rights reserved.