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 c omplemented at least by XRD geometries giving other information. There fore the following geometries are compared: conventional powder diffra ctometry in Bragg-Brentano geometry, asymmetric diffraction used for s tress measurement in the so-called OMEGA- and psi- goniometer geometri es, and Seemann-Bohlin diffractometry. Advantages and drawbacks of the methods are briefly estimated. A short review of basic methods for th e characterization of texture, stress and lattice defects is given. Sp ecific effects frequently observed for hard coatings (e.g. the anisotr opy of lattice parameters and XRD line broadening) are discussed, toge ther with some of the possible reasons. Quantitative estimations are g iven for different types of lattice defects and elastic anisotropy. Th e crystallite group method is found to be useful for thin films.