Journal
JOURNAL OF MATERIALS CHEMISTRY A
Volume 5, Issue 41, Pages 21658-21662Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c7ta07667c
Keywords
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Funding
- EPSRC [EP/L027348/1]
- Science and Technology Facilities Council [1620186]
- CONACYT under Becas CONACYT al extranjero [327115]
- EPSRC [EP/L027348/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [EP/L027348/1] Funding Source: researchfish
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Na0.5Bi0.5TiO3 (NBT) perovskite is often considered as a potential lead-free piezoelectric material but it can also be an excellent oxide-ion conductor (M. Li et al., Nature Materials, 13, 2014, 31-35). Here we report the non-stoichiometry and oxide-ion conductivity of undoped and acceptor-doped NBT. A range of acceptor-type ions with varying doping levels are selected to incorporate into NBT or Bi-deficient NBT (nominal Na0.5Bi0.49TiO2.985; NB0.49T). Low levels of acceptors (typically < 2 at%) can be doped on both cation sites of NBT by an ionic compensation mechanism to create oxygen vacancies and are therefore effective in enhancing the bulk oxide-ion conductivity to values of similar to 2 mS cm(-1) at 400 degrees C. A maximum enhancement of less than 1 order of magnitude is achieved using either A-site Sr (or Ca) or B-site Mg doping in NB0.49T. This conductivity maximum is in good agreement with an oxygen-vacancy diffusivity limit model in a perovskite lattice proposed by R. A. De Souza (Advanced Functional Materials, 25, 2015, 6326-6342) and suggests that optimisation of the ionic conductivity in NBT has been achieved. Our findings on NBT illustrate that this approach should be applicable to other acceptor-doped perovskite oxides to determine their electrolyte (oxide-ion) conductivity limit.
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