Complete thermodynamic description of the Mg-Ca-O phase diagram including the Ca-O, Mg-O and CaO-MgO subsystems

A complete thermodynamic description of the Mg-Ca-O system and phase diagrams is developed. It is based on our extensive thermodynamic analysis of solid CaO and MgO data and validation of the low-temperature Mg-Ca-O phase diagram up to 1050 K. This work presents the high- temperature oxygen solubilities and revisions of calculated melting points of the oxides. An extension of the empirical schemes for predicting the activity coefficient of oxygen in liquid elements is proposed to predict data for the Mg-O system. Consistent thermodynamic descriptions of the complete binary Ca-O and Mg-O systems are developed. It is shown that this framework is crucial to understand recently measured significantly different melting points of CaO under oxidizing versus reducing conditions. The revised description of the MgO-CaO quasibinary oxide system considers all experimental data, revealing significantly different melting equilibria compared to all previous publications.