Activity determination in the alumina–dysprosia system by Knudsen effusion mass spectrometry

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.

► Vaporization of Al-Dy-O mixtures has been investigated by KEMS.
► The problem of attainment of thermodynamic equilibrium has been described.
► The activities of Al2O3 and Dy2O3 have been measured at T = 2130 K.
► The Gibbs energies and enthalpies of compound formation have been determined.