COMPLEX XRD MICROSTRUCTURAL STUDIES OF HARD COATINGS APPLIED TO PVD-DEPOSITED TIN FILMS .1. PROBLEMS AND METHODS

Conventional X-ray powder diffractometry is often insufficient for the study of the specific microstructure of hard coatings. It should be complemented at least by XRD geometries giving other information. Therefore the following geometries are compared: conventional powder diffractometry in Bragg-Brentano geometry, asymmetric diffraction used for stress measurement in the so-called OMEGA- and psi- goniometer geometries, and Seemann-Bohlin diffractometry. Advantages and drawbacks of the methods are briefly estimated. A short review of basic methods for the characterization of texture, stress and lattice defects is given. Specific effects frequently observed for hard coatings (e.g. the anisotropy of lattice parameters and XRD line broadening) are discussed, together with some of the possible reasons. Quantitative estimations are given for different types of lattice defects and elastic anisotropy. The crystallite group method is found to be useful for thin films.