Thermodynamic Properties of Wustite (FeO₁₊y)

Abstract

E.m.f. measurements of the cell, Pt/FeO₁₊y/ZrO₂ (CaO)/Ni-NiO/Pt, have been carried out to investigate the thermodynamic characteristics of wustite (FeO₁₊y). From these results, the relationship between temperature, oxygen pressure and composition of wustite and the phase boundaries of wustite phase in the binary system Fe-O were obtained and compared with those given by Darken and Gurry. The thermodynamic quantities such as activities of iron and oxygen in wustite, partial molar enthalpies and entropies of solution of oxygen in wustite and free energy of formation of magnetite were also evaluated. The defect sturcture of wustite was discussed in relation with the Po₂ dependence of cation vacancy concentration of wustite.