Why Are There So Few Perovskite Ferroelectrics?

TL;DR

This paper investigates why ferroelectricity is rare in perovskites, revealing that cation displacements, rather than octahedral rotations, are key to suppressing or enabling ferroelectricity, guiding future material design.

Contribution

It identifies the critical role of cation displacements in suppressing ferroelectricity and provides strategies for designing new ferroelectric perovskites based on symmetry and first-principles calculations.

Findings

Cation displacements suppress ferroelectricity more than octahedral rotations.

Rotations alone do not fully suppress ferroelectricity at low tolerance factors.

Guidelines for designing new ferroelectric perovskite materials.

Abstract

We use a combination of symmetry arguments and first-principles calculations to explore the connection between structural distortions and ferroelectricity in the perovskite family of materials. We explain the role of octahedral rotations in suppressing ferroelectricity in these materials and show that, as the tolerance factor decreases, rotations alone cannot fully suppress ferroelectricity. Our results show that it is cation displacements (`hidden' in Glazer notation) that accompany the rotations, rather than the rotations themselves, that play the decisive role in suppressing ferroelectricity in these cases. We use the knowledge gained in our analysis of this problem to explain the origin of ferroelectricity in $R3c$ materials such as FeTiO$_3$ and ZnSnO$_3$ and to suggest strategies for the design and synthesis of new perovskite ferroelectrics. Our results have implications not only for the fundamental crystal chemistry of the perovskites but also for the discovery of new functional materials.