Abstract
It is established that during the domain structure relaxation process after its removal from the equilibrium state by an alternating electric field, the sign of the coefficient c of the electric energy density decomposition in powers of a single polarization component changes from “+” to “–“. The signs of the coefficient c, obtained experimentally and assumed from the Landau-Ginzburg-Devonshire theory, coincide at the initial moment after “electric field annealing”.