Influence of Fe2O3 addition on the phase equilibrium for CaO-SiO2-TiO2 system at 1300 °C in air

Optimizing the Selective Crystallization and Phase Separation (SCPS) process is essential for improving the resource utilization of titanium-bearing blast furnace slag. However, the influence of Fe 2 O 3 addition on the phase equilibria of the CaO-SiO 2 -TiO 2 system remains insufficiently understood, particularly in Fe 2 O 3 -containing titanium-bearing slag systems. In this work, phase equilibria in the CaO-SiO 2 -TiO 2 system with 5 and 10 wt% Fe 2 O 3 additions were systematically investigated at 1300 °C in air using high-temperature equilibrium-quenching experiments, followed by characterization with XRD, SEM-EDS, and EPMA, along with thermodynamic calculations. Special attention was given to the influence of Fe 2 O 3 on the liquid-phase region and the liquid-CaTiO 3 two-phase coexistence region. The results show that the liquid region expands with increasing Fe 2 O 3 content, confirming its strong fluxing effect through stabilization of the liquid slag phase. Moreover, Fe 2 O 3 addition alters the liquid-CaTiO 3 phase equilibrium relationship and affects the distribution of Ti-bearing primary phase fields. Significant discrepancies were observed between the experimentally determined liquid-phase boundaries and FactSage predictions, with FactSage predicting a smaller liquid-phase region than that determined experimentally. The phase equilibrium data obtained in this study provide essential experimental information for thermodynamic model refinement of Fe 2 O 3 -containing CaO-SiO 2 -TiO 2 systems and offer theoretical guidance for optimizing the SCPS process and titanium-rich slag utilization.