Issue 32, 2021

Unveiling the mechanisms behind the ferroelectric response in the Sr(Nb,Ta)O2N oxynitrides

Abstract

Oxynitride perovskites of the type ABO2N have attracted considerable attention thanks to their potential ferroelectric behavior and tunable bandgap energy, making them ideal candidates for photocatalysis processes. Therefore, in order to shed light on the origin of their ferroelectric response, here we report a complete analysis of the structural and vibrational properties of SrNbO2N and SrTaO2N oxynitrides. By employing first-principles calculations, we analyzed the symmetry in-equivalent structures considering the experimentally reported parent I4/mcm space group (with a phase a0a0c in Glazer's notation). Based on the I4/mcm reference within the 20-atoms unit-cell, we found and studied the ensemble of structures where different octahedral anionic orderings are allowed by symmetry. Thus, by exploring the vibrational landscape of the cis- and trans-type configuration structures and supported by the ionic eigendisplacements and the Born effective charges, we explained the mechanism responsible for the appearance of stable ferroelectric phases in both anionic orderings. The latter goes from covalent-driven in the trans-type ordering to the geometrically-driven in the cis-type configuration. Finally, we found in both cases that the biaxial xy epitaxial strain considerably enhances such ferroelectric response.

Graphical abstract: Unveiling the mechanisms behind the ferroelectric response in the Sr(Nb,Ta)O2N oxynitrides

Article information

Article type
Paper
Submitted
21 Apr 2021
Accepted
21 Jun 2021
First published
21 Jun 2021

Phys. Chem. Chem. Phys., 2021,23, 17142-17149

Unveiling the mechanisms behind the ferroelectric response in the Sr(Nb,Ta)O2N oxynitrides

J. S. Gelves-Badillo, A. H. Romero and A. C. Garcia-Castro, Phys. Chem. Chem. Phys., 2021, 23, 17142 DOI: 10.1039/D1CP01716K

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