PROTON-CONDUCTIVE AND ELECTRON-CONDUCTIVE CERAMIC

A mixed proton-electron conducting ceramic is a metallic oxide having a perovskite type structure, includes at least one member selected from the group consisting of chromium (Cr) , manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and ruthenium (Ru) in a range of from 0.01 or more to 0.8 or less when a molar-ratio sum of metals constituting the metallic oxide is taken as 2, and has proton conductivity and electron conductivity.