STUDY ON PHASE-EQUILIBRIA IN THE NI-FE-O SYSTEM AT 1273-K

Phase equilibria were established between 1153 and 1213 K by varying the oxygen partial pressures. Besides thermogravimetric and quenching methods, electromotive force (EMF) measurements using calcia-stabilized zirconia were adopted to determine oxygen partial pressures in a CO//2-H//2 mixture. A nonstoichiometric spinel and metallic phases are observed in oxygen partial pressures between 10** minus **1**1**. **4**6 and 10** minus **1**2**. **4**5 Pa at 1153 K. The spinel-type solid solution is converted into FeO phase at lower pressures.