First-principles study of oxygen vacancies in LiNbO 3 -type ferroelectrics.

LiNbO 3 -type ferroelectric oxides, as an important class of non-centrosymmetric compounds, have received great attention due to their important and rich properties. Although oxygen vacancies are widely present, studies of them in LiNbO 3 -type ferroelectric oxides are rare. In this article, we consider three representative LiNbO 3 -type ferroelectric oxide materials LiNbO 3 , ZnTiO 3 and ZnSnO 3 to study the impact of oxygen vacancy doping using first principles calculations. LiNbO 3 and ZnTiO 3 have ferroelectrically active cations Nb 5+ and Ti 4+ , while ZnSnO 3 does not have ferroelectrically active cations. The distribution of the oxygen vacancy induced electrons are quite different in the three materials even though they have similar structures. In oxygen deficient LiNbO 3- δ ( δ = 0.083/f.u.), electrons are itinerant, while in ZnTiO 3- δ and ZnSnO 3- δ ( δ = 0.083/f.u.) the electrons are localized. These results provide guidance for the application of oxygen vacancies in LiNbO 3 -type ferroelectric material devices.