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

Abstract

Abstract The thermodynamic database for the ZrO 2 – La 2 O 3 – Y 2 O 3 – Al 2 O 3 system has been derived using previous descriptions for the six binary systems and the ternary ZrO 2 – La 2 O 3 – Al 2 O 3 system. The parameters of the Y 2 O 3 – Al 2 O 3 system were adjusted due to changes in the Y 2 O 3 thermody-namic parameters. The thermodynamic parameters of the La 2 O 3 – Y 2 O 3 system were slightly changed to get consistency between calculations and new experimental results for the ZrO 2 – La 2 O 3 – Y 2 O 3 ternary system. Diverse kinds of phase diagrams of the ZrO 2 – La 2 O 3 – Y 2 O 3 and La 2 O 3 – Y 2 O 3 – Al 2 O 3 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 Al 2 O 3 . The T 0 -lines have been calculated for diffusionless transformations between fluorite, tetragonal, monoclinic and pyrochlore phases in the ZrO 2 – LaO 1.5 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.