High-temperature reduction thermochemistry of SrVO3−δ

Abstract

Cubic SrVO3 perovskite oxide is an attractive candidate for high-temperature energy applications due to its favorable features such as multiple oxidation state cations, high structural and thermal stabilities, ability to accommodate a large number of oxygen vacancies, and cost-effectiveness. Herein, the temperature-dependent reduction properties of SrVO3 have been studied using accurate first-principles calculations to reveal the effects of oxygen vacancies and temperature on the reduction potential of SrVO3−δ , δ = 0–0.125. The reduction potential of SrVO3−δ was found to be significantly impacted by increasing oxygen vacancy concentration and temperature. Analysis of the electronic and vibrational properties of SrVO3−δ for differing δ revealed the origin of this reduction behavior. The electronic structure analysis shows that the reduction of SrVO3−δ upon oxygen vacancy formation is highly localized to the neighboring V4+ t2g states in the vicinity of the oxygen defect, irrespective of δ. A comparison of the vibrational density of states of defect-free and reduced SrVO3 demonstrated that the ionic contributions to the phonon density of states, and hence to the thermal contributions to the SrVO3−δ lattices, were significantly altered by the introduction of oxygen vacancies, which ultimately impacted the temperature-dependent reduction behavior of SrVO3−δ .