OXIDE-IONIC AND PROTONIC CONDUCTORS BASED ON PEROVSKITE-TYPE OXIDES AND THEIR POSSIBLE APPLICATIONS

Some perovskite-type oxides exhibit high ionic conductivity at elevated temperatures. Mobile ions in these solids are oxide ions or/and protons and sometimes the ionic conduction is accompanied with electronic conduction. Conduction in calcium titanate doped with aluminum is mainly oxide-ionic whereas calcium titanate doped with iron shows oxide-ionic and electronic mixed conduction. The ceramics based on perovskite-type oxides ABO3 whose B-site cations are relatively large in size behave as protonic conductors in an atmosphere containing hydrogen gas or steam at high temperature. Ytterbium-doped SrCeO3 is a typical example. Some ceramics based on BaCeO3 are mixed ionic conductors of oxide ions and protons. The properties of these ion conducting ceramics found by us and their possible applications are described in this paper.