Random local strain effects in homovalent-substituted relaxor ferroelectrics: a first-principles study of BaTi0.74Zr0.26O3

TL;DR

This study uses first-principles calculations to analyze how local strain effects from homovalent Zr substitution influence Ti displacements in relaxor ferroelectrics, revealing the role of cation size differences in structural disorder.

Contribution

It provides a detailed first-principles analysis of local strain effects and Ti displacement types in BaTi0.74Zr0.26O3, elucidating the structural mechanisms behind relaxor behavior.

Findings

Four types of Ti displacements identified, influenced by Zr/Ti distribution.

Local strain from size differences drives disordered Ti displacements.

Results applicable to understanding relaxor behavior in similar materials.

Abstract

We present first-principles supercell calculations on BaTi0.74Zr0.26O3, a prototype material for relaxors with a homovalent substitution. From a statistical analysis of relaxed structures, we give evidence for four types of Ti-atom polar displacements: along the < 1 1 1 >, < 1 1 0 >, or < 1 0 0 > directions of the cubic unit cell, or almost cancelled. The type of a Ti displacement is entirely determined by the Ti/Zr distribution in the adjacent unit cells. The underlying mechanism involves local strain effects that ensue from the difference in size between the Ti4+ and Zr4+ cations. These results shed light on the structural mechanisms that lead to disordered Ti displacements in BaTi(1-x)Zr(x)O3 relaxors, and probably in other BaTiO3-based relaxors with homovalent substitution.