Finite-Temperature Properties of Ba(Zr,Ti)O$_3$ Relaxors From First Principles

TL;DR

This paper introduces a first-principles-based method to study Ba(Zr,Ti)O$_3$ relaxor ferroelectrics across temperatures, addressing key questions about their microscopic mechanisms and the nature of polar nanoregions.

Contribution

It develops a novel ab-initio-based computational scheme to analyze relaxor ferroelectrics' properties and mechanisms, providing new microscopic insights.

Findings

Clarifies the nature of critical temperatures in relaxors

Provides evidence on the existence and formation of polar nanoregions

Questions the role of random fields and strains in relaxor behavior

Abstract

A first-principles-based technique is developed to investigate properties of Ba(Zr,Ti)O$_3$ relaxor ferroelectrics as a function of temperature. The use of this scheme provides answers to important, unresolved and/or controversial questions, such as: what do the different critical temperatures usually found in relaxors correspond to? Do polar nanoregions really exist in relaxors? If yes, do they only form inside chemically-ordered regions? Is it necessary that antiferroelectricity develops in order for the relaxor behavior to occur? Are random fields and random strains really the mechanisms responsible for relaxor behavior? If not, what are these mechanisms? These {\it ab-initio-based} calculations also leads to a deep microscopic insight into relaxors.