Vaporization in the Al2O3–MgO system

Abstract

The pseudobinary system Al₂O₃–MgO has been studied in the temperature range 1750–2100 K by the Knudsen effusion method in combination with mass spectrometric analysis of the vapor phase. Over the entire composition range, except for the 100 mol % Al₂O₃ boundary, the vapor phase over the system consists of three species: Mg, O₂, and O. The partial pressures obtained have been used to construct a p–x section through the Al₂O₃–MgO phase diagram at 1900 K. The standard enthalpy of formation of the MgAl₂O₄ spinel at 298 K has been determined by third-law calculations:–2301.61 ± 11.00 kJ/mol. We have derived equations for the temperature dependences of the partial pressures of the vapor species over the Al₂O₃–MgO system.