MIXED PROTONIC-ELECTRONIC CONDUCTION IN TRANSITION-METAL-DOPED PEROVSKITE-TYPE OXIDES

Protonic-electronic mixed conductors are of particular interest due to their variety of possible applications. Some acceptor-doped perovskites known as high-temperature proton conductors (HTPCs) are counted as solid electrolytes because they have quite small electronic conductivities in moist reducing atmospheres. In this paper, mixed protonic-electronic conduction has been investigated for transition-metal doped perovskite-type oxides, intending to add electronic conductivity to the base HTPCs. The mixed conduction was experimentally suggested for Y-doped BaCeO₃ and SrZrO₃ when they are co-doped with ruthenium. These materials actually showed hydrogen permeability with respect to the ambipolar diffusion ensuring the ionic-electronic mixed conduction. The mixed-conducting mechanism is revealed by electrochemical and spectroscopic measurements.