Thermodynamic Assessment of the CaO-SiO2-Sc2O3 Ternary System.

Sustainable utilization of Sc₂O₃-containing metallurgical slag has attracted great interest in industries and the academic community in recent years. As the primary subsystem, the CaO-SiO₂-Sc₂O₃ ternary system plays an essential role in recovering Sc₂O₃ from metallurgical slag. However, few thermodynamic data have been reported for Sc₂O₃-containing metallurgical slag systems, which greatly limits the sustainable utilization of Sc₂O₃. Therefore, based on the current phase diagram, thermodynamic and crystal structure data, the thermodynamic modeling of the CaO-SiO₂, CaO-Sc₂O₃, and SiO₂-Sc₂O₃ binary systems and CaO-SiO₂-Sc₂O₃ ternary system. The thermodynamic parameters of CaO-SiO₂-Sc₂O₃ system over the whole composition range are optimized with computer coupling of phase diagrams and thermochemistry approach. The modified quasi-chemical model and polynomial expansions of the excess Gibbs energy were used to simulate the liquid slag and solid solution, respectively. The solid phases are treated as stoichiometric compounds. A thermodynamic description of the CaO-SiO₂-Sc₂O₃ ternary system and its Sc₂O₃-containing binary subsystem was given. The optimized phase diagram of the CaO-SiO₂-Sc₂O₃ ternary system is in good agreement with the experimental data. The thermodynamic database generated in this study can be used to predict the high-temperature metallurgical recovery of Sc₂O₃ from calcia- and silica-containing slags. [ABSTRACT FROM AUTHOR]