First-principles effective Hamiltonian calculations of the electrocaloric effect in ferroelectric BaxSr1−xTiO3

Abstract

Ferroelectric materials possess largest thermal response upon variations of the applied electric field, however, the magnitude corresponding to electrocaloric effect (ECE) is relatively too small for cooling applications. Theoretical insight is therefore required to provide additional information, leading to better understanding of the electrocaloric effect with enhanced performance. In this work, electrocaloric effect in BaxSr1−xTiO3(BST) ferroelectric ceramics is calculated from first-principles based effective Hamiltonian. The influence of the electric field and concentration on ferroelectric properties of BaxSr1−xTiO3 are investigated in detail. In particular, we have studied the polarization and pyroelectric coefficient as a function of temperature in order to examine the ECE. With increasing amount of Ba, the critical temperature Tc is diffused and shifted towards higher temperature range. In addition, the adiabatic temperature change ΔT of BaxSr1−xTiO3 is also predicted with particular focus on the applied electric field and concentration x. Hence, the electrocaloric effect performance was determined by the feature of the phase transition. Our results also reveal particular contribution of the field gradient primarily on the magnitude of adiabatic temperature change, leading to volume expansion, and thus improvement of ECE. Investigations in a wide temperature range also revealed large ECE shifted towards higher temperature to achieve ΔT⋍ 3.0 K for x = 1.0. An enhancement of ECE is therefore envisaged to show the usefulness of this material, which will be a step forward to experimentally synthesis this compound for more elucidations.