Vacancy-Mediated Oxide-Ion Conduction in the Palmierite-like Layers of Ba6Nb2Na2V2O17

Abstract

Various hexagonal perovskite derivatives have recently been demonstrated to exhibit high oxide ion conductivity, with their conductivity properties repeatedly being linked to palmierite-like (P-L) structural layers. Here, we report an investigation into the crystal structure and electrical properties of the hexagonal perovskite derivative Ba6Nb2Na2V2O17. Ba6Nb2Na2V2O17 exhibits oxide ion conductivity, with a total conductivity of 1.8 × 10–6 S cm–1 at 650 °C under an atmosphere of flowing dry N2. Unlike other oxide ion conducting hexagonal perovskite derivatives, Ba6Nb2Na2V2O17 is shown not to feature interstitial oxygen, mixed coordination polyhedra, or isolated polyhedra. Regardless, oxide ion conductivity is still enabled by the P-L structural motif. These results hence further emphasize the utility and versatility of P-L layers in the context of ionic conductivity. Our atomistic modeling reveals a distinct vacancy-mediated oxide-ion conduction pathway, predominantly involving the O1 and O2 sites of the P-L layer.