Epitaxial zirconia films on sapphire substrates

The epitaxial development of undoped zirconia films produced via the solution precursor route and deposited by dip-coating on (11 (2) over bar 0) planes of sapphire is investigated. After drying and firing at 600 degrees C, polycrystalline 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}(tZrO2)//(11 (2) over bar 0)(sapphire) and {111}(tZrO2)//(11 (2) over bar 0)(sapphire). In-plane growth of flat {100} oriented crystals can be favored by varying the thickness and firing conditions of the films. The heteraepitaxial orientation of the pseudo single crystalline him and the interface structure are examined through X-ray diffraction experiments (low incidence XRD, omega-rocking curves) and cross sectional HRTEM observations. (C) 1998 Elsevier Science S.A. All rights reserved.