“…Crystallographic features of the structure [14][15][16][21][22][23][24], functional properties [4,5,8,15,22] and thermal expansion [21,25,26] of simple and complex metastable oxide systems remain a subject of particular attention due to future prospects for their practical application. At the same time, systematic studies of thermal stability of metastable solid solutions depending on the nature of the substituent cations have not been performed, and such data are absent in the literature.…”