Oxide-ion conduction in the Dion–Jacobson phase CsBi2Ti2NbO10−δ

Oxide-ion conductors have found applications in various electrochemical devices, such as solid-oxide fuel cells, gas sensors, and separation membranes. Dion–Jacobson phases are known for their rich magnetic and electrical properties; however, there have been no reports on oxide-ion conduction in this family of materials. Here, for the first time to the best of our knowledge, we show the observation of fast oxygen anionic conducting behavior in CsBi 2 Ti 2 NbO 10− δ . The bulk ionic conductivity of this Dion–Jacobson phase is 8.9 × 10 −2 S cm −1 at 1073 K, a level that is higher than that of the conventional yttria-stabilized zirconia. The oxygen ion transport is attributable to the large anisotropic thermal motions of oxygen atoms, the presence of oxygen vacancies, and the formation of oxide-ion conducting layers in the crystal structure. The present finding of high oxide-ion conductivity in rare-earth-free CsBi 2 Ti 2 NbO 10− δ suggests the potential of Dion–Jacobson phases as a platform to identify superior oxide-ion conductors. Oxide ion conductors are an exciting class of materials with applications in various domains. Here, the authors show that Dion–Jacobson Phases are a structure supporting high O 2− mobility. The bulk conductivity of CsBi 2 Ti 2 NbO 10− δ even exceeds that of YSZ, offering new possibilities in electrolyte discovery.