Tetragonal La2BaIn2O7 belongs
to the stoichiometric n = 2 members of the Ruddlesden–Popper
(RP) structure, with La3+ and Ba2+ cations ordered
in the rock salt and octahedral layers, respectively. Herein, a series
of alkaline-earth-metal-doped materials La2–x
M
x
BaIn2O7–0.5x
(M = Ca, Sr, Ba) were prepared by the traditional
solid-state reaction method. The results revealed that the substitutions
of Ca/Sr/Ba for La introduced oxygen vacancies and led to good oxide
ion conduction, e.g., ∼1.21 × 10–3–1.38
× 10–2 S/cm within 600–900 °C for
the specimen La1.7Ba1.3In2O6.85, which was more than 2 orders of magnitude higher than the parent
material. However, both the parent and acceptor-doped La2BaIn2O7 showed very limited proton conductions.
The energetics of defect formation and oxygen vacancy migrations in
La2BaIn2O7-based materials was studied
through the static lattice and molecular dynamics (MD) atomistic simulations
based on the interatomic potential approach. The defect formation
energy calculations for the electrons and holes in La2BaIn2O7 rationalized the experimentally observed pure
ionic conduction under low pO2 and mixed ionic and p-type
electronic conductions under high pO2, respectively. The
MD simulations indicated two-dimensional oxygen vacancy migration
within the perovskite slab for the acceptor-doped La2BaIn2O7.