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

Publication date: Available online 28 October 2019Source: Physics Letters AAuthor(s): M. Tarnaoui, M. Zaim, M. Kerouad, A. ZaimAbstractFerroelectric 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 primary on the magnitude of adiabatic temperature change, leading to volume expansion, and thus improvement of ECE. Invest...

Source: Physics Letters A - October 29, 2019 Category: Physics Source Type: research