Protonic Conduction in Oxides at Elevated Temperatures and Their Possible Applications

Protonic conduction in oxide ceramics under hydrogen-containing atmosphere at elevated temperatures is reviewed with respect to oxide materials, their electrochemical properties, conduction mechanism and possible applications. These oxides are unique in respect of the fact that they have no protons as a host component, but incorporate protons via reactions with the atmosphere. The materials of this class are some perovskite-type oxides and other oxides which contain crystal defects. Defect equilibria for proton formation in these kinds of oxides are discussed citing some experimental results. Possible electrochemical devices using proton conducting ceramics are briefly introduced.