Calculation of multicomponent ceramic phase diagrams

Abstract

A data base is being developed for calculation of quasi-binary and quasi-ternary phase diagrams of ceramic systems. Previous segments of this base cover combinations of Cr 2O 3, MgO, Al 2O 3, SiO 2, CaO, Si 3N 4, AlN, BeO, Y 2O 3 and Ce 2O 3. Lattice stability, solution and compound phase parameters have been derived covering the liquid, spinel, corundum, periclase, crystobalite, tridymite, quartz, hexagonal and beta prime phases which appear in the binary systems composed of pairs of these compounds. Compound phases formed from specific binary combinations of these compounds (i.e. MgO·Cr 2O 3) have been characterized. This description is based on observed thermochemistry and phase diagrams for the binary systems of interest. Selected ternary systems have been computed using the foregoing data base for comparison with experimental sections in order to illustrate the usefulness of the data base. To date, 66 quasi-binary and 19 quasi-ternary systems have been calculated. The most recent set of papers extend the base to cover GeO 2, HfO 2, ZrO 2 and TiO 2. The components are the particular interest in recent developments of structural high temperature ceramics and applications requiring unusual toughness. The current work deals with four quasi-binary systems and four quasi-ternary systems which have been calculated over a wide range of temperatures. These samples demonstrate the capability of the data base and computational model for dealing with phase equilibria in multicomponent oxide systems over a wide range of conditions and compositions of practical interest.