Thermodynamic properties of quaternary systems based on hafnia: a high-temperature mass spectrometric study and modeling

The composition of vapor over ceramic samples of the La 2 O 3 −Sm 2 O 3 −Y 2 O 3 −HfO 2 and La 2 O 3 −Sm 2 O 3 −ZrO 2 −HfO 2 systems, the vaporization rates of the samples, and the thermodynamic properties of components of the systems mentioned above were studied for the first time by Knudsen effusion mass spectrometry at T = 2330 K. The lanthanoid oxide activities in these systems demonstrated negative deviations from ideal behavior. The experimental lanthanoid oxide activity values were compared with the results of calculations by the semiempirical Kohler, Redlich-Kister, and Wilson methods as well as based on the generalized lattice theory of associated solutions carried out using the data for corresponding binary systems. It was established that, among the semiempirical methods considered, Wilson’s approach provides the best agreement with the experimental data when calculating the thermodynamic properties of multicomponent systems.