Activity Determination in the Alumina-Dysprosia System by Knudsen Effusion Mass Spectrometry

Abstract

The vaporization of Al-Dy-O mixtures has been investigated by the Knudsen effusion mass spectrometry technique. The saturated vapor has been found to consist of the atoms Al, O and the molecules AlO, Al2O, DyO. At the initial stage the vaporization of Dy2O3 and Al2O3-Dy2O3 mixtures was found to be incongruent and accompanied by some loss of oxygen. An attainment of congruently vaporizing composition and equilibrium state takes quite a long time. The activities of binary oxides have been measured at T = 2130 K. The Gibbs energies and enthalpies have been derived for formation of the compounds Dy4Al2O9, DyAlO3 and Dy3Al5O12 from sesquioxides.