A. LaBaInO, C. ruddlesden-popper structure, D. proton conductivity, E. IR spectroscopy, SYSTEM, TRANSPORT-PROPERTIES, CHEMICAL-STABILITY, proton conductivity, IR spectroscopy, OXYGEN, LaBaInO4, DOUBLE PEROVSKITES, ruddlesden-popper structure, FLUORINE, OXIDE-ION CONDUCTIVITY, BA2IN2O5, CELL