The relevance of the study and the scope of the materials based on oxides of rare earth elements are considered. The main results of the study of vaporization processes and thermodynamic properties in multicomponent systems containing oxides of rare earth elements, both by high-temperature mass spectrometry and using model approaches, are presented. The need for further study of the high-temperature behavior of systems containing rare earth elements both by experimental methods of high-temperature chemistry and within the framework of model approaches is shown in order to create a national database of thermodynamic properties and models for predicting the physicochemical properties in oxide systems and materials.