The problems of studying low-temperature phase formation in systems, which are the basis for obtaining functional materials, are selected. The use of salt fluxes (alkali metal nitrates and sulfates) is an effective method of accelerating the achievement of equilibrium in fluoride and oxide systems. Extrapolation of phase equilibria to absolute zero temperature, taking into account the requirements of the third law of thermodynamics, is a powerful method for obtaining relevant information. Summary phase diagrams of the ZrO2-Sc2O3 and albite — anorthite systems are proposed.