Phase Diagram of the System La2O3-Fe2O3

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The phase diagram of the system La2O3-Fe2O3 was determined by X-ray diffraction, melting point measurements and microscopic observations. Since the dissociation of Fe2O3 into Fe2O4+1/2O2 was observed above 1400°Cin air, specimen materials were treated at 1 atmospheric pressure of oxygen in the case of heating above 1400°C. The dissociation pressure of Fe2O3 attains to 1 atm. at 1490°C, so even the use of 1 atmospheric pressure of oxygen is insufficient to prevent the thermal reduction of Fe2O3 above this temperature, especially in the case of heating the specimens to melting points. But the measurements were carried out with the expectation that the melting points would not differ seriously even if the oxygen defects are introduced by the dissociation. LaFeO3 is the only intermediate compound found in this system, which melt incongruently at 1850°C. The eutectic reaction, LaFeO3+Fe2O3 ?? liquid, was also observed at 1490°C, 83.3 mol% Fe2O3. The mutual solid solubilities between compounds in this system (i.e. La2O3, LaFeO3 and Fe2O3) were not observed. Ferromagnetic compound, which is producible by heating at 1400°-1420°C in air accom-panied with the dissociation of a part of Fe2O3, is not confirmed in our present experiments performed at 1 atmospheric pressure of oxygen.
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