Thermodynamic analysis of the metal - oxygen systems

The method of thermodynamic modeling of systems involving phases of variable composition (solid metal and liquid solution, compounds with deviations from stoichiometry) is described. This method is demonstrated on the example of the metal - oxygen systems (Cr-O, Mn-O, Fe-O and Ni-O). The technique relies on the use of the sublattice model and the polynomial Redlich-Kister model. The approaches for thermodynamic description of liquid and solid oxygen solutions in a metal, as well as oxides of different composition and structural type (MeO, Me 3O 4 and Me 2O 3) are demonstrated. Expressions for the Gibbs energies of phases are presented. The phase diagrams of four systems, based on the described techniques, have been created, as well as the temperature dependences of the oxygen potential for the studied systems. The results of calculations are compared to experimental data. The provided information can be used in order to analyze the more complex systems, including those important in industry.