Fe-Si-O

Calculating the iron-saturated section in “FeO”-SiO2 (ac(fe,fcc)=1), there is still some amount of Fe2O3 in the liquid as is shown in this example using the TCS Metal Oxide Solutions Database (TCOX).

Calculated "FeO"-SiO2 phase diagram.

Figure 1: Calculated "FeO"-SiO2 phase diagram.

The upper part shows the Fe2O3 content in the slag at the liquidus.

Figure 2: Magnification of the calculated "FeO"-SiO2 phase diagram. The upper part shows the Fe2O3 content in the slag at the liquidus.

Reference

[1997Sel] M. Selleby, An assessment of the Fe-O-Si system. Metall. Mater. Trans. B. 28, 563–576 (1997).