Revisiting the Kittel's model of antiferroelectricity: phase diagrams, hysteresis loops and electrocaloric effect.

We revisit the Kittel's model of antiferroelectricity by extending the model to study the phase transitions, hysteresis loop behaviors and electrocaloric effect (ECE) of antiferroelectrics (AFEs). By considering both the first- and second-order AFEs, explicit expressions for the physical and staggered polarizations of AFEs in the stable states are derived. We also obtain the analytical solutions for describing the dielectric susceptibilities of AFEs in the AFE and paraelectric (PE) phases. Coercive fields in AFE are also derived and studied. To verify the usefulness of the Kittel's model of antiferroelectricity, we apply the model to systematically investigate the phase transitions, hysteresis loops and ECEs of PbZrO(PZO). By adopting appropriate values of the Kittel's parameters for first-order transition, analytical and numerical results are obtained and discussed. Our results show that PZO exhibits a complex temperature ()-electric field () phase diagram, consisting of the AFE, ferroelectrics, ferrielectric, PE and mixed phases. Thephase diagram is qualitatively agreed with the new AFE model that was derived based on symmetry by Tolédano and Khalyavin (2019B024105). We found that the calculated zero-field dielectric susceptibility is qualitatively and quantitatively agreed with experimental results. We show that the polarizations and dielectric susceptibilities of PZO in heating and cooling deviate from each other, as expected for the first-order materials. Our calculated results also reveal that the ECE in PZO has an electro-heating of Δ≈ +6.5 °C and an electro-cooling of Δ≈ -4.0 °C, respectively, which are comparable to the experimental results.