Computer modelling of Bi12TiO20: Intrinsic defects, ion migration and rare earth ion incorporation

Abstract This paper reports a computer modelling study of Bi12TiO20, a material of interest for a range of optical applications. Using potentials transferred from studies of BGO and BaTiO3, the structure is modelled giving excellent agreement with experimental data. The intrinsic defect properties of the material are then calculated, leading to Frenkel and Schottky energies, and the prediction of the most likely form of defect disorder in the material. Oxygen ion migration is then studied, given the interest in the material as a potential oxygen ion conductor, and activation energies are reported. Finally, doping of the material by rare earth ions is considered, and solution energies are calculated for substitution at both bismuth and titanium sites. These enable the preferred substitution site to be predicted, and conclusions to be drawn about the relative ease of substitution of different rare earth ions.