Influence of defects on ferroelectric and electrocaloric properties of BaTiO$_3$

TL;DR

This study investigates how various defects influence the ferroelectric and electrocaloric behaviors of BaTiO₃, revealing that defects can modify transition temperatures, polarization, and caloric effects, including inducing an inverse caloric response.

Contribution

It combines ab initio molecular dynamics with defect modeling to show how defects alter ferroelectric and electrocaloric properties of BaTiO₃, including transition temperature shifts and inverse caloric effects.

Findings

Defects modify transition temperatures and polarization.

Large caloric response persists despite defects.

Polar defects broaden the caloric response and induce inverse effects.

Abstract

We report modifications of the ferroelectric and electrocaloric properties of BaTiO$_3$ by defects. For this purpose, we have combined \textit{ab initio}-based molecular dynamics simulations with a simple model for defects. We find that different kinds of defects modify the ferroelectric transition temperatures and polarization, reduce the thermal hysteresis of the transition and are no obstacle for a large caloric response. For a locally reduced polarization the ferroelectric transition temperature and the adiabatic response are slightly reduced. For polar defects an intriguing picture emerges. The transition temperature is increased by polar defects and the temperature range of the large caloric response is broadened. Even more remarkable, we find an inverse caloric effect in a broad temperature range.