Revealing the impact of acceptor dopant type on the electrical conductivity of sodium bismuth titanate

Solid solutions of sodium bismuth titanate (NBT) belong to the most performant lead-free dielectric ceramics for energy storage. However, the defect chemistry of NBT is very complex, and acceptor doping can lead to an unexpected and extraordinarily high oxygen ionic conductivity. This can be attributed to a non-linear change in the formation of defect associates between acceptor and oxygen vacancy with increasing acceptor doping. Using different acceptor dopants with varying concentrations, we elucidate the interaction between acceptors and oxygen vacancies in this work. With the help of total energy calculations based on density functional theory and molecular dynamics simulations, the experimentally observed differences in conductivity can be rationalized.