Predicting Dielectric Properties of Ferroelectric Materials with Point Defects by a Phase-Field Model

Relaxor ferroelectrics, designed through the doping of point defects in normal ferroelectrics, exhibit remarkable dielectric properties. Nevertheless, the precise mechanism underlying the impact of point defect doping on the dielectric properties remains enigmatic, particularly in materials harboring a morphotropic phase boundary. Based on the phase-field model, we conducted simulations to investigate the influence of point defects on the dielectric constants of two materials: doping BaTiO₃ and PbZrTiO₃. A diagram illustrating the ferroelectric-relaxor ferroelectric domain was constructed, elucidating the intricate relationship among the temperature, defect concentration, and polarization states. Notably, the dielectric constant peaks with an increase in defect points, gradually shifting toward lower temperatures. Furthermore, by constructing a free energy surface, we uncovered the root cause of the elevated dielectric constant associated with defect points. The findings of this study offer profound insights into the role of point defects in influencing the dielectric constant, providing valuable knowledge for future materials design and optimization.