Redox stability of Ba 2In 2O 5-doped compounds

Abstract

High temperature cyclic voltammetry was successfully applied to the determination of the electrochemical stability range of several fast oxide ion conductors: Ba 2In 2O 5 and the derived compounds Ba 2In 2 − x Me x O 5 + δ (ME = V, Mo, W). Experiments performed at 600 °C revealed a good stability for Ba 2In 2O 5. 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 Mo 6+ → Mo 4+ and V 5+ → V 3+ 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 h 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% H 2 atmosphere at 600 °C, the crystal structure is maintained. All studied compositions exhibit p-type electronic conduction properties.