CHARACTERIZATION OF EPITAXIAL ZrO₂ BY X-RAY DIFFRACTOMETRY WITH PARALLEL BEAM GEOMETRY.R. Guinebretiere, A. Dauger, O. Masson, B. Soulestin Laboratoire de Materiaux Ceramiques et Traitements de Surfaces UA CNRS ndeg.320-ENSCI-47 Av. A. Thomas - 87065 Limoges France

The epitaxial growth of tetragonal zirconia produced via a metal-organic precursor route and deposited on the (h00) planes of MgO substrates was characterized with an original X-ray diffractometer. A parallel CuK[[alpha]]₁ X-ray radiation incident beam is provided by a rotating anode source through a four reflections monochromator made of two chapel-cut germanium single crystals. The flat specimen is fixed at controlled incidence angle on the four circle diffractometer. Data are collected with a Curved Position Sensitive Detector (INEL CPS 120). The CPSD angular calibration procedure first proposed for capillary sample setting has been extended to the case of flat plate samples. A specific specimen positioning procedure is used and the d-spacing measurement accuracy has been checked using NIST Silicon standard sample.

A zirconia precursor sol was first prepared in the zirconium n-propoxide - acetylacetone - n-propanol system, deposited by dip l coating on the polished (100) face of a MgO crystal and then heat treated l for 1.5 hour at successive temperatures ranging from 600 to 1400deg.C. A polycristalline thin film of tetragonal zirconia nanosized grains first appeared. Sintering and normal grain growth simultaneously occurred. Then the film began to break up into isolated islands. At high temperature, the size of single grained islands increased rapidly, up to about 1um after 1.5 hour at 1400deg.C, and complete epitaxial orientation with respect to the substrate was observed: <100>_zr02 //<100> _mg0 and { l00} _zr02//{ 100} _mg0. The breadth of t-ZrO₂ (200) rocking curve demonstrated the very low level of misorientations. The modification of the substrate (200) and (400) rocking curves was related to surface strains. The interface was imaged by transmission electron microscopy on cross sectional thin samples.