Design of a low band gap oxide ferroelectric: Bi$_6$Ti$_4$O$_{17}$

TL;DR

This paper proposes a method to design low band gap oxide ferroelectrics using charge imbalance, demonstrated through first principles studies of a hypothetical compound Bi$_6$Ti$_4$O$_{17}$, which is predicted to be ferroelectric with a reduced band gap.

Contribution

The study introduces a new design strategy for low band gap oxide ferroelectrics and predicts a novel compound with desirable electronic properties.

Findings

Bi$_6$Ti$_4$O$_{17}$ is ferroelectric with reduced polarization.

The band gap of Bi$_6$Ti$_4$O$_{17}$ is significantly lower at 1.83 eV.

First principles calculations support its potential as a low band gap ferroelectric.

Abstract

A strategy for obtaining low band gap oxide ferroelectrics based on charge imbalance is described and illustrated by first principles studies of the hypothetical compound Bi$_6$Ti$_4$O$_{17}$, which is an alternate stacking of the ferroelectric Bi$_4$Ti$_3$O$_{12}$. We find that this compound is ferroelectric, similar to Bi$_4$Ti$_3$O$_{12}$ although with a reduced polarization. Importantly, calculations of the electronic structure with the recently developed functional of Tran and Blaha yield a much reduced band gap of 1.83 eV for this material compared to Bi$_4$Ti$_3$O$_{12}$. Therefore, Bi$_6$Ti$_4$O$_{17}$ is predicted to be a low band gap ferroelectric material.