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The thermodynamic properties of the Sm2O3–Y2O3–HfO2 system at 2500 K were modeled based on the generalized lattice theory of associated solutions using experimental data obtained by high-temperature mass spectrometry. A comparison was made between the results of the calculations of the thermodynamic properties of the Sm2O3–Y2O3–HfO2 system using two independent approaches to modeling based on this theory: from the experimental data on the properties of the ternary system and from the data on its boundary binary systems Sm2O3–Y2O3, Sm2O3–HfO2, and Y2O3–HfO2. It was shown that the chemical potentials of the components that were calculated in the studied ternary system using the above approaches much better fit the experimental data in the former case.

Ultrafine Nd2Hf2O7 powders with the pyrochlore structure are prepared by self-propagating hightemperature synthesis (in the Pechini version). The elemental and phase composition of the powder are studied. Microstructure is studied by scanning electron microscopy. BET specific surface areas are determined. Thermal behavior is studied by TGA/DSC/DTA up to 1473 K. The sintering kinetics of as-synthesized Nd2Hf2O7 powder at various temperatures is studied. Nd2Hf2O7 vaporization in the range 2400–2600 K is studied by Knudsen effusion/mass spectrometry, and the thermodynamic characteristics of this compound are determined.

Silicon evaporation has been investigated by high-temperature mass spectrometry, and the saturation vapor pressure of silicon over its melt has been determined over the temperature range from 1739 and 2326 K. The saturation vapor pressure data obtained via silicon evaporation from Knudsen cells made of molybdenum, tungsten, molybdenum disilicide-lined molybdenum, and graphite silicided by the gas-phase method are compared. Among these materials, silicided graphite is the most inert toward silicon vapor. The silicon partial pressures measured in the silicided graphite cell are close to the recommended values.

Spatial separation of activator oxides in MnO2 + PbO and MnO2 + V2O5 binary compositions helps to locate the interactions between the oxides that lead to nonlinear joint effects of the compositions on GaAs thermal oxidation. The mutual enhancement of the chemostimulating activity (a positive nonlinear effect) was discovered in the solid phase, whereas vapor-phase processes led to a considerable negative nonadditivity of the joint chemostimulating effect.

Spatial separation of the oxides in MnO2 + PbO and MnO2 + V2O5 binary compositions activating the thermal oxidation of GaAs has made it possible to locate the interactions between these oxides that are responsible for the nonlinear effects observed in their coaction. The solid-phase interactions enhance the chemostimulating activities of both oxides (a positive nonlinear effect takes place). The gas-phase interactions cause a marked negative deviation from the additive chemical stimulation effect.

The vaporization of individual lead and vanadium oxides and a wide range of compositions of PbO-V2O5 melts has been studied. The thermodynamic characteristics of the PbO-V2O5 system have been determined, PbO-V2O5 melts show negative deviations from the ideal behavior because of the formation of thermally stable compounds in their condensed phase. For gaseous lead vanadate PbV2O6, the thermodynamic functions have been calculated and the standard enthalpies of formation and atomization have been determined.