State transition and electrocaloric effect of BaZr$_{x}$Ti$_{1-x}$O$_3$: simulation and experiment

TL;DR

This study combines simulations and experiments to analyze the electrocaloric effect and phase transitions in BaZr$_{x}$Ti$_{1-x}$O$_3$, revealing how Zr concentration influences its properties and potential applications.

Contribution

It provides a comprehensive analysis of BZT's electrocaloric effect across different Zr concentrations using both simulation and experimental methods, highlighting optimal compositions for applications.

Findings

ECE peaks decrease with increasing Zr concentration.

Relaxor features become prominent at intermediate Zr levels.

High Zr concentration results in almost nonpolar, low ECE materials.

Abstract

The electrocaloric effect (ECE) of BaZr$_{x}$Ti$_{1-x}$O$_3$ (BZT) is closely related to the relaxor state transition of the materials. This work presents a systematic study on the ECE and the state transition of the BZT, using a combined canonical and microcanonical Monte Carlo simulations based a lattice-based on a Ginzburg-Landau-type Hamiltonian. For comparison and verification, experimental measurements have been carried on BTO and BZT ($x=0.12$ and $0.2$) samples, including the ECE at various temperatures, domain patterns by Piezoresponse Force Microscopy at room temperature, and the P-E loops at various temperatures. Results show that the dependency of BZT behavior of the Zr-concentration can be classified into three different stages. In the composition range of $ 0 \leq x \leq 0.2 $, ferroelectric domains are visible, but ECE peak drops with increasing Zr-concentration harshly. In the range of $ 0.3 \leq x \leq 0.7 $, relaxor features become prominent, and the decrease of ECE with Zr-concentration is moderate. In the high concentration range of $ x \geq 0.8 $, the material is almost nonpolar, and there is no ECE peak visible. Results suggest that BZT with certain low range of Zr-concentration around $x=0.12 \sim 0.3 $ can be a good candidate with relatively high ECE and simutaneously wide temperature application range at rather low temperature.