Study on Phase Equilibria in the Ni–Fe–O System at 1273 K

Abstract

The phase equilibria in the Ni–Fe–O system were established at several temperatures between 1153 and 1213 K by varying the oxygen partial pressures. Besides thermogravimetric and quenching methods, electromotive force (EMF) measurements composed of calcia-stabilized zirconia were adopted in order to determine the oxygen partial pressures in an atmosphere of a CO₂–H₂ mixture.
A nonstoichiometric spinel and metallic phases are observed in the oxygen partial pressures between 10^−11.46 and 10^−12.45 Pa at 1153 K. The spinel-type solid solution is converted into FeO phase at much lower oxygen pressures.