Sodium ion conduction in perovskite-type sodium lanthanum niobate ceramics

The electrical conductivity of Na x La (1− x )/3 NbO 3 ceramics has been studied over a composition range of 0.15 ≤ x ≤ 0.45 to identify optimal conductivity conditions and to elucidate the structural and chemical factors affecting the Na + ion conductivity. The composition with x = 0.25 achieves the highest total conductivity of 7.0 × 10 −4 S cm −1 at 350 °C, with Na + ion transference number of unity. The random distribution of Na, La and vacancy in the two crystallographically independent A sites in perovskite structures significantly impacts the conductivity. In addition, Na x La (1− x )/3 NbO 3 perovskite ceramics exhibit high dielectric constants (ε r = 220−470) and suppressed electronic conductivity, making them potentially beneficial as an interfacial material to mitigate chemical potential differences between electrolytes and electrode active materials. • Sodium ion conductivity of perovskite-type solid-state electrolyte. • Solid-state electrolyte ceramics with high dielectric constant. • Relationship between ionic conductivity and site occupancy.