Silica Activity and Raman Spectra of the CaO-SiO2-TiOx System

The thermodynamic activity of SiO 2 in CaO-SiO 2 -TiO x slags was measured by the slag-metal-gas equilibrium method. Slags containing up to 43 mol% TiO x , were equilibrated with molten copper in molybdenum crucibles in H 2 -H 2 O-Ar gas atmosphere. The oxygen partial pressure and temperature were maintained at ∼10 -12 atm and 1873 K, respectively. In the equilibrated slags, the proportion of titanium in the reduced Ti 3+ state ranged from 16% to 54% of total Ti by mass. Results showed that at a given CaO/SiO 2 ratio, the activity coefficient of SiO 2 increases with increasing TiO x concentration. Samples of CaO-SiO 2 -TiO x slags were also examined by Raman spectroscopy. Raman spectra obtained for oxidised and reduced CaO-SiO 2 -TiO x slags show that the Ti 4+ ion has a tetrahedral coordination, while the coordination of Ti 3+ appears to be predominantly octahedral. These findings are consistent with the observed effect of titania on the silica activity in the CaO-SiO 2 -TiO x slags.