Experimental investigation and thermodynamic modeling of the ZrO2–MgO–Al2O3 system

Solid state equilibria of the ZrO2–MgO–Al2O3 system as well as the equilibria including liquid were investigated in the whole compositional range using high temperature DTA, X-ray diffraction (XRD) and scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM/EDX). Isothermal sections at 1523, 1873 and 2023 K were constructed and the formation of the ternary X-phase in the MgO-rich region was confirmed. According to our results it forms by the peritectic reaction MgO + Spinel + L ⇄ X at 2114 K and decomposes by the X ⇄ F + MgO + Spinel reaction at 1894 K. The ternary mixing parameter of liquid was assessed using the results of melting experiments. The obtained liquid thermodynamic description was used to derive enthalpy and entropy values of the X phase. The calculated liquidus and solidus representing 5 invariant processes as well as calculated isothermal and vertical sections show good consistency with the results obtained in this work and those available in the literature.