Thermodynamic study of sodium–iron oxides

Studies on ternary phase diagrams of the Na–Fe–O system have been carried out from the thermodynamic point of view. Thermodynamic data of main ternary Na–Fe oxides Na4FeO3(s), Na3FeO3(s), Na5FeO4(s) and Na8Fe2O7(s) have been assessed. A user database has been created by reviewing literature data together with recent DSC and vapor pressure measurements by the present authors. New ternary phase diagrams of the Na–Fe–O system have been constructed from room temperature to 1000 K. Stable conditions of the ternary oxides at 800 K were presented in predominance diagram as functions of oxygen pressure and sodium pressure.