Phase equilibria in the titanium-iron-oxygen system

Phase relations and the equilibrium partial pressures of oxygen in the titanium-iron-oxygen ternary system have been studied in the temperature range of 1173 to 1373 K by means of a thermogravimetric method in a CO-CO₂ gas mixtures and X-ray diffraction technique for the quenched samples after the equilibrium experiments. The objective of this study is both to clarify the relation between the phase relations in the Ti-Fe-O ternary system and the equilibrium partial pressures of oxygen, and to discuss the possibility of upgrading natural ilmenite ore to a rutile substitute for extractive metallurgy of titanium. The results are summarized as follows: The phase diagram and isobars of oxygen in the titanium-iron-oxygen ternary system at 1173, 1273 and 1373 K have been determined. From the present results upgrading ilmenite (FeTiO₃) to a rutile (TiO₂) substitute is possible thermodynamically. Both the activities of magnetite and ulvospinel show negative deviations from Raoult's law in the Fe₃O₄-Fe₂TiO₄ solid solutions coexisting with metallic iron at 1173-1373 K.