[en] This paper considers the interrelation between the thermal stability of the resonance frequency and electronegativity of the constituent elements of the solid solutions, taken in the appropriate degree of oxidation. It is shown that the thermal stability of the resonance frequency of solid solutions of multicomponent systems increases with increasing electronegativity of the cations, i.e., with increasing degree of covalence of the chemical bonds and the attendant ferroelectric elastance of the solid solutions