Phase Equilibrium in the Y-Fe-O System at 1000℃

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Phase equilibrium was established in the Y-Fe-O system at 1000℃ with an oxygen partial pressure ranging from -log (Po2/atm)=0 to 16.15, allowing construction of a phase diagram of the Y2O3-Fe-Fe2O3 system at 1000℃. Y2O3, Fe, FeO, Fe3O4, Fe2O3, and YFeO3 were found to be stable in the system. Y3Fe5O12 and YFe2O4 were not found in the system. The present results were different form those of previous work at 1200℃, in which YFe2O4 and Y3Fe5O12 were stable together with YFeO3, and also different from those of previous work at 1100℃, in which only Y3Fe5O12 was stable together with YFeO3 as the ternay compounds. Nonstoichiometric ranges were found in the FeO phase, with the composition of FeO represented as a function of log (Po2/atm), No/NFe = 4.635 × 10-2 log Po2 + 1.747. Activities of components in the solid solution were calculated from the equation. YFeO3 lattice constants, prepared in air by the quenching method, were determined and compared with previous values. These were in good agreeement with previous values. The Gibbs energy changes of the reaction 1/2 Y2O3 + Fe + 3/4 O2 = YFeO3, appearing in the phase diagram, were calculated from the oxygen partial pressures in equilibrium, and the value obtained was compared with previous values.
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