Thermodynamics of phase transitions in the subsolidus domain of the FeO–MgO–TiO2 system

Abstract

This paper gives consideration to the three-component FeO–MgO–TiO2 system that is a part of the four-component MgO–Al2O3–FeO–TiO2 system which serves to produce materials with valuable properties. The structure of binary FeO–TiO2 and MgO–TiO2 systems is described and the available data on the FeO–MgO–TiO2 system are analyzed. We present the thermodynamic data on all system compounds and calculate change of the free Gibbs energy in the temperature range of 800 to 1900 K for three exchange reactions. It was established that the triangulation of the FeO–MgO–TiO2 system changes in three following temperature ranges: at the temperatures of up to 1115 К, at 1115 to 1413 К (the restructuring of conodes here occurs) and above 1413 K (stable pseudobrookite is formed). It was shown that the following two-phase equilibria are stable: MgTi2O5–FeTiO3, FeTiO3–MgTiO3, MgTiO3–Fe2TiO4, Fe2TiO4–Mg2TiO4 and Mg2TiO4–FeO at the temperatures of up to 1115 K; MgTi2O5–FeTiO3, FeTiO3–MgTiO3, FeTiO3–Mg2TiO4, Fe2TiO4–Mg2TiO4 and Mg2TiO4–FeO in the temperature range of 1115 to 1413 K; and MgTi2O5–FeTi2O5, MgTi2O5–FeTiO3, FeTiO3–MgTiO3, FeTiO3–Mg2TiO4, Fe2TiO4–Mg2TiO4 and Mg2TiO4–FeO at the temperatures of above 1413 K.