As reported by Ming Li et al., the A-site non-stoichiometry as well as the B-site acceptor doping of Na0.5Bi0.5TiO3 (NBT) shows a significant impact on the oxygen vacancy concentration and hence the ionic conductivity [1, 2]. Mg acceptor doped NBT, for instance, shows extremely high ionic conductivity comparable with conventionally used solid ion conductor materials. Related to the experience with other lead based or lead free ferroelectric ceramics, this behavior was a rather unexpected result. The origin and defect chemical reasons for these results are part of important ongoing research approaches. In this work, we will discuss the formation and effect of oxygen vacancies B-site acceptor doped Na0.5Bi0.5TiO3. With the help of temperature dependent impedance spectroscopy (IS) the defect chemistry and the charge carrier migration process is investigated. Furthermore, phase and charge carrier dependent simulations are discussed to reach a deeper understanding of the origin for this unexpected conductivity behavior . From these results we are able to propose how the investigated changes to NBT may affect other NBT related materials.
. M. Li, M. J. Pietrowski, R. A. De Souza, H. Zhang, I. M. Reaney, S. N. Cook, J. A. Kilner, and D. C. Sinclair, Nat. Mater, 13, pp 31-35 (2014)
 M. Li, H. Zhang, N. S. Cook, L. Li, J. A. Kilner, I. M Reaney, and D. C. Sinclair, Chem. Mater., 27, pp 629-634, (2015)
 L. Koch, S. Steiner, K.-C. Meyer, I.-T. Seo, K. Albe, T. Frömling, J. Mater. Chem. C, 5, 8958-8965 (2017)