Revealing the impact of acceptor dopant type on the electrical conductivity of sodium bismuth titanate
A combined experimental and theoretical study
2022/03/16 by K. Albe
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.
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Comparison of bulk conductivity at 500 °C for different dopants and concentrations. -
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Arrhenius plots of the bulk conductivity obtained from temperature dependent impedance spectroscopy of a) Mg-doped NBT, b) Fe-doped NBT, and c) Al-doped NBT. -
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Binding energy between the oxygen vacancy and an acceptor dopant (Mg, Al, and Fe) on the regular B-site after relaxation in the R3 structure. The schematic at the top illustrates the coordination shells on which the calculations have been performed.
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The work appeared here:
