A TMA and DSC study of the kinetics of the solid-state reaction in an Al2O3–Y2O3 system

Abstract

This study focuses on the kinetic analysis of the solid-phase reactivity of mixtures of Al₂O₃ and Y₂O₃ powders, introduced in stoichiometric proportions for the formation of the YAG phase (Y₃Al₅O₁₂). Structural and microstructural analyses using XRD, TEM, STEM, and SEM provided a better understanding of the reaction mechanism of the formation of the YAG phase, which appears to be of a heterogeneous nucleation-growth type. The second part of this study focused on a kinetic analysis of these reactions, using the Kissinger model applied to data obtained by differential scanning calorimetry (DSC) and thermomechanical analysis (TMA). Activation energies equal to 560 kJ mol⁻¹ for the formation of YAP and 660 kJ mol⁻¹ for the formation of the YAG phase were obtained by both methods, meaning that the reaction should be limited by the diffusion of Y³⁺ ions.