The novel brownmillerite-type oxyfluorides Ba2-0.5xIn2O5-xFx (x <= 0.30) were synthesized by solid state method. Their structure, microstructure, electrical properties and thermal stability have been investigated. These phases are capable of dissociative dissolution of water and can exhibit proton transport. Electrical conductivity and transport numbers were measured with varying T and pO(2) in dry (pH(2)O = 4.5 10(-4) atm) and wet (pH(2)O = 1.42 10(-2) atm) atmospheres. The F--transport numbers increase with increasing x and the temperature, although at the temperature T<600 degrees C the F--transport numbers are negligible. The concentration dependencies of the partial conductivities were discussed. It was established that small F--concentrations can improve the oxide-ion and the proton conductivities. (C) 201 1 Elsevier B.V. All rights reserved.