Thermodynamic modelling in the ZrO2–La2O3–Y2O3–Al2O3 system

Abstract

Abstract The thermodynamic database for the ZrO2 – La2O3 – Y2O3 – Al2O3 system has been derived using previous descriptions for the six binary systems and the ternary ZrO2 – La2O3 – Al2O3 system. The parameters of the Y2O3 – Al2O3 system were adjusted due to changes in the Y2O3 thermody-namic parameters. The thermodynamic parameters of the La2O3 – Y2O3 system were slightly changed to get consistency between calculations and new experimental results for the ZrO2 – La2O3 – Y2O3 ternary system. Diverse kinds of phase diagrams of the ZrO2 – La2O3 – Y2O3 and La2O3 – Y2O3 – Al2O3 ternary systems have been calculated. The present thermodynamic description of the quaternary system is consistent with available experimental results for lower-order systems. It was used to calculate isoplethal sections for compositions related to thermal barrier coating (TBC) and its interaction with thermally grown oxide Al2O3. The T 0-lines have been calculated for diffusionless transformations between fluorite, tetragonal, monoclinic and pyrochlore phases in the ZrO2 – LaO1.5 system as well as driving forces for partitioning of non-equilibrium phase into equilibrium phase assemblages. These data could be applied for determination of desirable ranges of material composition for TBC.