Phase relationship in the system MgO-V2O3 between 1661 and 1873 K at PO2=(3.55±0.2)×10-6 and (3.55±0.3)×10-5 Pa

Abstract

The composition ranges of the phases in the pseudo binary system MgO-V2O3 were studied between 1661 and 1873 K and at controlled oxygen partial pressures of (3.55 ± 0.2) × 10-6 and (3.55 ± 0.3) × 10-5 Pa. The phase relationship was determined by equilibrating MgO-V2O3 pellets in a CO-CO2 mixture followed by quenching and electron-probe microanalysis. To ensure sufficient quenching, a new setup was designed and developed, so that the equilibrated samples can be quenched in oil directly under the same atmosphere inside the experimental setup. Three different phases were found in the samples, namely MgO, MgO-V2O3 spinel and V2O3. The phase boundaries were determined with good reproducibility. The solubility of V2O3 in the MgO phase increased with temperature and was significantly higher than literature data. The spinel as well as the V2O3 composition range were found to change only a little with temperature in the investigated temperature range. Decreased oxygen potential led to a slight increase of the V2O3 content in the spinel phase and V2O3 phase. Furthermore, decreased oxygen potential resulted in a significant increase of the solubility of V2O3 in the MgO phase at the higher temperatures, especially at 1873 K.