High Oxide-Ion Conductivity through the Interstitial Oxygen Site in Sillén Oxychlorides
Yaguchi, Hiroshi, Daisuke Morikawa, Takashi Saito, Kenji Tsuda, and Masatomo Yashima
Advanced Functional Materials
Oxide-ion conductors are gaining attention as future materials in energy applications, such as solid oxide fuel cells. Many Bi-containing compounds exhibit high oxide-ion conductivity via conventional vacancy mechanism. However, interstitial oxide-ion conduction is rare in Bi-containing materials. Herein, high oxide-ion conductivity is reported through interstitial oxygen sites in Sillén oxychlorides, LaBi2−xTexO4+x/2Cl (Bi2LaO4Cl-based oxychlorides). Oxide-ion conductivity of LaBi1.9Te0.1O4.05Cl is 20 mS cm−1 at 702 °C, and higher than best oxide-ion conductors as Bi2V0.9Cu0.1O5.35 below 201 °C. Despite of the presence of Bi and Te species, LaBi1.9Te0.1O4.05Cl shows extremely high chemical and electrical stability at 400 °C from oxygen partial pressure 10−25 to 0.2 atm and high chemical stability under CO2 flow, wet 5% H2 in N2 flow, and air with natural humidity. Neutron scattering length density analysis, DFT calculations, and ab initio molecular dynamics simulations indicate that the extremely high oxide-ion conduction is attributed to cooperative diffusion through interstitial oxygen sites (interstitialcy diffusion mechanism) in triple fluorite-like layers. The present findings demonstrate the ability of LaBi2−xTexO4+x/2Cl as superior oxide-ion conductors, which can open new horizons for oxide-ion conductors.
solid oxide fuel cells