BaTa_0.5Li_0.5O_2.5: a new highly oxygen deficient perovskite oxide-ion conductor

High oxide-ion and proton conductivity in perovskite oxides has been well documented in the literature. Herein, we report a highly oxygen deficient perovskite oxide BaTa0.5Li0.5O2.5 (BTLO) as a new oxide-ion conductor. The material exhibits a simple primitive cubic perovskite structure (S.G.: Pm3m) with lattice parameter a = 4.1024(1) angstrom and completely disordered Ta and Li cations on the B-site. The ionic conduction is predominated by oxide-ion over a wide range of oxygen partial pressure and temperature, with an ionic conductivity comparable to the state-of-the-art yttria-stabilized zirconia. Ab initio molecular dynamics (AIMD) simulations reveal that oxide-ion diffusion follows three-dimensional pathways, involving oxygen vacancy hopping along the edges of (Ta/Li)O-4 tetrahedra and (Ta/Li)O-6 octahedra. This work may inspire future work to discover new oxide-ion conductors in similar systems.