Phase equilibrium in the system Y-Fe-O at 1100 deg. C

Phase equilibrium was established in the Y-Fe-O system at 1100 deg. C by varying the oxygen partial pressure from -log(PO2/atm)=15.00 to 0, allowing construction of a phase diagram at 1100 deg. C for the system Y2O3-Fe-Fe2O3. In the system, two ternary compounds, YFeO3 and Y3Fe5O12, were stable and had nonstoichiometric composition, whereas YFe2O4 was not found to be stable. The present result was different from that of previous studies at 1200 degree sign C, in which YFe2O4 was stable, along with the above two ternary compounds. Lattice constants of YFeO3 and Y3Fe5O12, prepared in air by a quenching method, were determined and compared with previous values, and showed close agreement. The standard Gibbs energy changes of the reactions in the Fe-O system, Fe+1/2O2=FeO, 3FeO+1/2O2=Fe3O4, and 2/3Fe3O4+1/6O2=Fe2O3, were determined, and the obtained values were compared with the previous values. The standard Gibbs energy changes of the reactions, Fe+1/2Y2O3+3/4O2=YFeO3, and 3YFeO3+2/3Fe3O4+1/6O2=Y3Fe5O12, were calculated from the oxygen partial pressures in equilibrium