Redox stability of Ba2In2O5-doped compounds

High temperature cyclic voltammetry was successfully applied to the determination of the electrochemical stability range of several fast oxide ion conductors: Ba2In2O5 and the derived compounds Ba2In2-xMexO5-delta (ME=V, Mo, W). Experiments performed at 600 degrees C revealed a good stability for Ba2In2O5, Its redox stability extends up to -1 V-/ROE. This potential corresponds to a 8.10(-24) atm oxygen partial pressure. This material could then be compatible with the conditions of use of a fuel cell. In contrast, molybdenum and vanadium derivatives are more reducible. The Mo6+ -> Mo4+ and V5+ -> V3+ redox reactions are to be considered. For tungsten doped compounds, cyclic voltammetry revealed a better stability. But, a small shift of Bragg peaks was observed on a sample with composition x=0.1 after 20 It under an atmosphere containing 1.5% H-2. However, whatever the dopant, the reduction process doesn't reach the metal and, under a 1.5% H2 atmosphere at 600 degrees C, the crystal structure is maintained. All studied compositions exhibit p-type electronic conduction properties. (c) 2007 Elsevier B.V. All rights reserved.