Design of a low band gap oxide ferroelectric: Bi₆Ti₄O₁₇

¹ Physics Department, National University of Singapore - 2 Science Drive 3, Singapore 117542, Singapore
² College of Physics and Communication Electronics, Jiangxi Normal University - Nanchang, Jiangxi 33022, PRC
³ Materials Science and Technology Division, Oak Ridge National Laboratory - Oak Ridge, TN 37831-6114, USA

^a singhdj@ornl.gov

Received: 15 March 2011
Accepted: 1 April 2011

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 Bi₆Ti₄O₁₇, which is an alternate stacking of the ferroelectric Bi₄Ti₃O₁₂. We find that this compound is ferroelectric, similar to Bi₄Ti₃O₁₂ 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 Bi₄Ti₃O₁₂. Therefore, Bi₆Ti₄O₁₇ is predicted to be a low band gap ferroelectric material.