Experimental Study on the Thermodynamics of the CaO-SiO₂-Ce₂O₃ System at 1873 K

The phase relations in the CaO-SiO₂-Ce₂O₃ system under the reducing atmosphere at 1873 K were determined by the conventional equilibrium and quenching method combined with scanning electron microscopy-electron probe microanalysis (SEM-EPMA) and X-ray diffraction (XRD) measurements on the quenched samples. Based on these analyses, a large part of the isothermal phase diagram was constructed. Furthermore, the thermodynamic activities of Ce₂O₃ in the melts at 1873 K were measured by the chemical equilibrium method. Using the measured activity data, an empirical formula to estimate the activity coefficient of Ce₂O₃ was proposed based on the regular solution model. It was found that, for the melts with the same Ce₂O₃ contents, the thermodynamic activities of Ce₂O₃ increase gradually with the rise of basicity (the ratio of CaO to SiO₂) of the melts. This implies that, from the thermodynamic point of view, the increase of basicity is favorable to the enrichment and precipitation of Ce-containing mineral phases.