Improved oxide-ion conductivity by substitution of Sr for Bi in Dion-Jacobson phase CsBi2Ti2NbO10

Abstract

Oxide ion conducting ceramics have attracted much attention due to their various applications such as solid oxide electrolysis cells (SOECs) and solid-oxide fuel cells (SOFCs). Herein, we present the first report on the preparation, electrical and structural properties of oxide-ion conducting Dion-Jacobson phases CsBi1.9M0.1Ti2NbO9.95 (M = Mg, Ca, Sr and Ba). It was found that partial substitution of Bi3+ by Sr2+ improves the conductivity of CsBi2Ti2NbO10. The electrical conductivity of CsBi1.9Sr0.1Ti2NbO9.95 is approximately 2 times higher than that of CsBi2Ti2NbO10 at 600–900 °C and is 1.65 × 10−2 S cm−1 at 900 °C. The improvement of oxide-ion conductivity in CsBi1.9Sr0.1Ti2NbO9.95 can be attributed to the increase of the carrier (oxygen vacancy) concentration and small size mismatch between the dopant Sr and host Bi cations. The electrical conductivities of CsBi1.9Sr0.1Ti2NbO9.95 are almost constant in the oxygen partial pressure region from 10−25 to 1 atm at 600 °C, indicating the predominant oxide-ion conduction and high chemical and electrical stability. Bond-valence-based energy landscapes of a test oxide ion in CsBi1.9Sr0.1Ti2NbO9.95 suggest that oxide ions migrate along the edges of the octahedra in the inner perovskite layers, leading to two-dimensional oxide-ion diffusion. This study demonstrates the successful improvement of oxide-ion conductivity by the substitution in Dion-Jacobson phase, which would develop the science and technology of Dion-Jacobson type oxide-ion conductors.