Ultrafast phase-field model of frequency-dependent dielectric behavior in ferroelectrics

Relaxor ferroelectrics have applications in transducers and capacitors owing to their dielectric relaxation. Although the existence of polar nanoregions (PNRs) inside the relaxor ferroelectrics contributes to enhancing the dielectric response, the dielectric relaxation mechanism remains unclear in the wide frequency range from kHz to THz. In this study, we investigated the frequency-dependent (10³–10¹² Hz) dielectric properties using ultrafast phase-field simulations. The dielectric response is divided into the matrix response, the “collinear” PNR response, and the “non-collinear” PNR response. Among them, the collinear PNR response accounts for 90% of the dielectric constant enhancement. The response behavior of collinear PNRs has a higher frequency limitation than that of non-collinear PNRs. The different relaxation times of the collinear PNR lead to a corresponding distinct rotation for the polar vectors. Finally, we investigate the different response behaviors of the polarization in the PNR from the aspect of energy barriers. This study not only promotes the understanding of wide-range frequency-dependent dielectric relaxation processes but also guides the design of ultrafast relaxor ferroelectric devices in the future.