Oxygen ion conductors

Ionic conductors have always provided a fascinating interdisciplinary field of study ever since their discovery by Faraday at the Royal Institution in London over 200 years ago. More recently, and particularly in the past decade, the pace of research has been rapid, driven by the requirements for new clean energy sources, sensors, and high energy density batteries. A very interesting subgroup of this class of materials are the oxides that display oxygen ion conductivity. As well as the intrinsic interest in these materials, there has been a continued drive for their development because of the promise of important technological devices such as the solid oxide fuel cell (SOFC), oxygen separation membranes, and membranes for the conversion of methane to syngas1. All of these devices offer the potential of enormous commercial and ecological benefits provided suitable high performance materials can be developed. In this article we will review the materials currently under development for application in such devices with particular reference to some of the newly discovered oxide ion conductors.