Giant electrocaloric effect around T$_c$

TL;DR

This study reveals a giant electrocaloric effect in lithium niobate near its ferroelectric transition, with potential applications in cooling and energy harvesting, and suggests this behavior is universal among ferroelectrics and similar materials.

Contribution

The paper demonstrates the existence of a giant electrocaloric effect around T_c in LiNbO₃ using molecular dynamics and first-principles-based modeling, highlighting a universal behavior in ferroelectrics.

Findings

Giant electrocaloric effect occurs near T_c in LiNbO₃.

Maximum ECE aligns with the Widom line and ferroelectric instability.

The behavior is likely universal among ferroelectric materials.

Abstract

We use molecular dynamics with a first-principles-based shell model potential to study the electrocaloric effect (ECE) in lithium niobate, LiNbO$_3$, and find a giant electrocaloric effect along a line passing through the ferroelectric transition. With applied electric field, a line of maximum ECE passes through the zero field ferroelectric transition, continuing along a Widom line at high temperatures with increasing field, and along the instability that leads to homogeneous ferroelectric switching below $T_c$ with an applied field antiparallel to the spontaneous polarization. This line is defined as the minimum in the inverse capacitance under applied electric field. We investigate the effects of pressure, temperature and applied electric field on the ECE. The behavior we observe in LiNbO$_3$ should generally apply to ferroelectrics; we therefore suggest that the operating temperature for refrigeration and energy scavenging applications should be above the ferroelectric transition region to obtain large electrocaloric response. We find a relationship among $T_c$, the Widom line and homogeneous switching that should be universal among ferroelectrics, relaxors, multiferroics, and the same behavior should be found under applied magnetic fields in ferromagnets.