Divergent electrostriction at ferroelectric phase transitions: example of strain-induced ferroelectiricty in KTaO3

TL;DR

This paper reveals that electrostriction in ferroelectrics like KTaO3 diverges at phase transitions, leading to giant responses, and introduces new calculation methods and design principles for advanced electromechanical materials.

Contribution

It challenges the assumption of constant electrostriction across phase boundaries and provides a microscopic explanation for giant electrostrictive responses in ferroelectrics.

Findings

Electrostriction diverges with permittivity at the transition.

Giant electrostrictive responses are achievable in KTaO3.

New calculation methods for ferroelectric electrostriction are proposed.

Abstract

We investigate the electrostrictive response across a ferroelectric phase transition from first-principles calculations and refute the prevailing view of constant electrostriction across the ferroelectric phase boundary. We take as a case study the epitaxial strain-induced transition from para- to feroelectricity of \ce{KTaO3}. We show that the magnitude of the electrostriction diverges with the permitivity at the transition, hence exhibiting giant responses through a calculation of both the M and Q electrostrictive tensors. We explain the origin of this giant electrostrictive response in \ce{KTaO3} using a microscopic decomposition of the electrostriction coefficients, and use this understanding to propose design rules for the development of future giant electrostrictors for electromechanical applications. Finally, we introduce a further means to calculate electrostriction, specific to ferroelectrics, and not yet utilised in the literature.