CONCENTRATION WAVE APPROACH IN STRUCTURAL AND THERMODYNAMIC CHARACTERIZATION OF CERAMIC CRYSTALS

This review provides an account of a new approach to the theoretical determination of the structure of some ceramic compounds. It is an extension of a previous survey on ordering in substitutional and interstitial solid solutions. The authors reformulate the concentration wave concept used in the statistical thermodynamics and crystallography of order-disorder transformations and then apply it to new situations, namely, stoichiometric ceramic compounds. The ceramics structure determination, however, requires some extension of the concentration wave formalism, namely, the introduction of a stability criterion which is referred to as the maximum amplitude principle. The survey includes a general formulation of the concentration wave concept and the maximum amplitude principle, its applications to the structure determination of metal oxides based on the bcc host lattice (TiO//2, alpha -PbO//2, corundum, the Ti//nO//2//n// minus //1 series, etc. ) and oxides based on the fcc host lattice with octahedral and tetrahedral occupancies (CuO, Ag//2O, As//2O//3, Se//2O//3, Sc//4Ti//3O//1//2, pyrochlores, crystobalite SiO//2, CoWO//4, CaTiO//3, the Magneli phase series Mo//nO//3//n// minus //1, etc. ), and a discussion of the spinel structure stability.