Electrophysical properties investigation of Ba$_{0.8}$Sr$_{0.2}$TiO$_{3}$ ferroelectric films in paraelectric state

Phenomenological analytical expressions relating the ferroelectric film capacity to the coefficients of free energy decomposition in accordance to the degrees of substance polarization in paraelectric state are obtained. High-frequency capacitance-voltage characteristics of metal–Ba$_{0.8}$Sr$_{0.2}$TiO$_{3}$–metal structures have been measured at the temperatures above the transition point from ferroelectric phase to paraelectric one. The comparison of theoretical and experimental data has been resulted in plotting the dependences of Ba$_{0.8}$Sr$_{0.2}$TiO$_{3}$ film polarization on external voltage and determining the values of the parameters of the theory of phase transitions of second kind of Ginsburg–Landau for the objects under investigation.