We present an approach to the modeling of phase diagrams in coordinate electric fields versus temperature for model antiferroelectrics (AFE) ${\mathrm{PbZrO}}_3$ (PZO) and ${\mathrm{PbHfO}}_3$ (PHO). The essence of this method is the approximate restoration of the planar difference in the Gibbs energy $\left[\mathrm{\Delta }G\right(T,E)$] between different phases (i.e., $Pbam$, $R3c$, $R3m$, $Cm2m$) using experimental phase diagrams. This allows to recalculate $E\text{−}T$ diagrams for an arbitrary field direction. The calculated diagrams have a predictive ability, so it will be useful for future experimental works, while the analysis of the obtained thermodynamical parameters emphasizes interesting peculiarities of PZO-like AFE materials. Among them are (i) the presence of low-polarization (that may be ferrielectric) phases below and above room temperature, (ii) the presence of both a positive and negative electrocaloric effect in the different parts of the wide $E\text{−}T$ area, and (iii) the physical reason for phase boundary linearity in perovskite PZO-like materials. Since our method uses a combination of experimental data and modeling, it could serve as the bridge between experimental data and atomistic modelings, which, as we show, do not match well the experimental part so far. We are convinced that the Gibbs energy approach itself is rather general and portable on other materials (e.g., ${\mathrm{BaTiO}}_3$) and coordinates, such as pressure ($p$) and concentrations ($x$). It also can be supplemented with ferrielectric phases from current related works with the aim to solve the pending problem of the description of their energy balance.

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• Dielectric properties
• Electric polarization
• Ferroelectricity
• Phase transitions
• Thermodynamics
• Antiferroelectrics
• Ferroelectrics