Epitaxial zirconia films on sapphire substrates

The epitaxial development of undoped zirconia films produced via the soluti on precursor route and deposited by dip-coating on (11 (2) over bar 0) plan es of sapphire is investigated. After drying and firing at 600 degrees C po lycrystalline films are made of nanosized randomly oriented tetragonal ZrO2 grains. Firing at higher temperatures promotes grain growth and islanding, so producing a layer of heteroepitaxial but isolated grains. Two families of single crystalline islands are identified: {100}(iZro2)//(11 (2) over ba r 0)(sapphire) and {111}(tZrO2)//(11 (2) over bar 0)(sapphire). In-plane gr owth of flat {100} oriented crystals can he favored by varying the thicknes s and firing conditions of the films. The heteroepitaxial orientation of th e pseudo single crystalline film and the interface structure are examined t hrough X-ray diffraction experiments flow incidence XRD, omega-rocking curv es and cross sectional HRTEM observations. (C) 1998 Elsevier Science S,A. A ll rights reserved.