Modeling of polar nanoregions dynamics on the dielectric response of relaxors

A master equation for describing the polar nanoregions (PNRs) dynamics with adaptive-volume-dependent activation energy barrier has been established based on mean field approximation to investigate the anomalous temperature-and frequency-dependent dielectric properties of relaxor ferroelectrics. In the proposed model, the activation energy was correlated with the applied electric field and mean volume of PNRs. By expressing the PNRs mean volume as a function of temperature and pressure, and then fitting it to some existing experimental data, the results obtained reproduced the experimentally observed dielectric response including the broad temperature- and frequency-dependent peaks, frequency shift and dispersion of susceptibility. Finally, it has been found that the pressure and applied electric field led to the decrease of the PNRs relaxation time, and thus the peak of the real part of the dielectric constant was shifted to a lower temperature, which is consistent with the existing experimental data. The present study shows that polar cluster dynamics provides a better understanding of the macroscopic dielectric properties of relaxor ferroelectrics. (C) 2013 AIP Publishing LLC.