The frequency-dependent polarization switching in nanograined BaTiO₃ films under high-strength electric field

The polarization reorientation in ferroelectric nanomaterials under high-strength AC electric fields is intrinsically a frequency-dependent process. However, the related study is not widely seen. We report a phase-field investigation regarding the dynamics of polarization switching and the electromechanical characteristics of a polycrystalline BaTiO₃ nanofilm under applied frequency from 0.1 to 80 kHz. The grain boundaries and the in-plane strains are considered in the model. The obtained hysteresis and butterfly loops exhibit a remarkable variety of shapes with the changing frequency. The underlying mechanism for the observed frequency-dependent physical properties was discussed via domain structure-based analysis. In addition, we examined the influence of the kinetic coefficient in the Ginzburg-Landau equation as well as the influence of the electric-field amplitude to the frequency dependency. It was found that a higher value of kinetic coefficient or field amplitude tends to enhance the mobility of polarization switching and to transform high-frequency characteristics to low-frequency ones.