Isothermal phase diagram of CaO–SiO2–Nb2O5–La2O3 system at 1300 °C and 1200 °C

Thermodynamic properties of CaO–SiO2–Nb2O5–La2O3 slag system are of great significance for the utilization and application of niobium and rare earth resources. In the present work, the phase equilibria in CaO–SiO2–Nb2O5–La2O3 system at 1300 °C and 1200 °C have been experimentally investigated. A total of 12 equilibrium phase regions have been determined in the constructed isothermal spatial phase diagram, including five four-phase regions: Liquid + SiO2+CaNb2O6+LaNbO4, Liquid + CaNb2O6+Ca2Nb2O7+LaNbO4, Liquid + Ca2Nb2O7+CaO·3SiO2·2La2O3+LaNbO4, Liquid +10CaO·6SiO2·Nb2O5+Ca2Nb2O7+LaNbO4, Liquid + LaNbO4+SiO2+CaO·3SiO2·2La2O3; six three-phase regions: Liquid + SiO2+LaNbO4, Liquid + CaNb2O6+LaNbO4, Liquid + Ca2Nb2O7+LaNbO4, Liquid + CaO·3SiO2·2La2O3+Ca2Nb2O7, L + CaNb2O6+Ca2Nb2O7, Liquid + SiO2+CaNb2O6; four two-phase regions: Liquid + SiO2, Liquid + CaNb2O6, Liquid + LaNbO4, Liquid + Ca2Nb2O7. Subsequently, the isothermal section of CaO–SiO2–Nb2O5-(5%, 10%, 15%, 20%, 25%, 30%) La2O3 pseudo-ternary systems have been obtained.