Insulating improper ferroelectric domain walls as robust barrier layer capacitors

TL;DR

This study demonstrates that insulating domain walls in improper ferroelectric h-ErMnO₃ create a stable internal barrier layer, leading to colossal dielectric permittivity suitable for advanced capacitor applications.

Contribution

It introduces a novel approach to engineer high-permittivity materials using topologically protected domain walls in improper ferroelectrics, unlike proper ferroelectrics.

Findings

High dielectric permittivity due to internal barrier layer capacitance

Insulating domain walls are topologically protected and stable under high electric fields

Volume fraction of internal BLC matches insulating domain wall volume fraction

Abstract

We report the dielectric properties of improper ferroelectric h-ErMnO$_3$. From the bulk characterisation we observe a temperature and frequency range with two distinct relaxation-like features, leading to high and even 'colossal' values for the dielectric permittivity. One feature trivially originates from the formation of a Schottky barrier at the electrode-sample interface, whereas the second one relates to an internal barrier layer capacitance (BLC). The calculated volume fraction of the internal BLC (of 8 %) is in good agreement with the observed volume fraction of insulating domain walls (DWs). While it is established that insulating DWs can give rise to high dielectric constants, studies typically focused on proper ferroelectrics where electric fields can remove the DWs. In h-ErMnO$_3$, by contrast, the insulating DWs are topologically protected, facilitating operation under substantially higher electric fields. Our findings provide the basis for a conceptually new approach to engineer materials exhibiting colossal dielectric permittivities using domain walls in improper ferroelecctrics with potential applications in electroceramic capacitors.