Oxide ion conduction in indium-oxide-substituted calcium zirconate

Indium-oxide-substituted calcium zirconate of the nominal composition CaZr0.9In0.1O3-delta is an important perovskite-type high-temperature proton conductor. In the present study, the transition from proton conduction to oxide ion conduction in this material has been investigated experimentally. A specially designed galvanic cell was employed, in which the oxygen chemical potential at the electrodes is determined by appropriate metal/metal-oxide mixtures while the hydrogen chemical potential is fixed by a gas atmosphere of known hydrogen partial pressure. Through cell voltage measurements at different temperatures proton and oxide ion conduction were discriminated, and conditions were identified under which virtually pure oxide ion conduction occurs despite the presence of a significant hydrogen partial pressure. Conductivity measurements allowed the determination of the activation energy of oxide ion conduction. The impact of a variable oxide ion vacancy concentration on the ion conducting properties of the solid electrolyte is discussed. (c) 2006 The Electrochemical Society.