Strain engineering on electrocaloric effect in PbTiO3 and BaTiO3

In isothermal processes, applying the electric field to ferroelectric materials will cause the vibrational entropy change (Delta S-vib) along with the corresponding adiabatic temperature change (Delta T-vib) induced by the intrinsic structure response, i.e., part of the electrocaloric effect (ECE). Most previous investigations only focused on the total ECE in different materials, but we found that strain engineering can regulate the ECE significantly in the typical ferroelectrics PbTiO3 and BaTiO3. In this paper, Delta S-vib and Delta T-vib in PbTiO3 and BaTiO3 are extracted using first-principles calculations and the effects of strains on the ECE are then studied. The results show that the isotropic compressive and tensile strains of up to 5% could regulate the thermodynamic properties of these materials effectively. Additionally, we find that compression can cause a positive ECE, while tension can cause a negative ECE, which is further verified by the change of Born effective charge. The calculations are accelerated (> 4x) by graphics processing units (GPUs) using the Compute Unified Device Architecture (CUDA). This method thus provides a new strategy for the regulation of Delta S-vib in the ECE.