Microstructural aspects of oxygen ion conduction in solids

The microstructure of solid electrolyte ceramics plays a key role in defining the level of ionic conduction of the material. The polycrystalline nature and the metastable state of most practically useful materials require that the conducting ion must negotiate a series of interfacial features during the conducting process. These features may either enhance or impede the conducting ions and include such things as precipitates, microdomains, various zone configurations and the ubiquitous grain boundaries. By combining the technique of impedance spectroscopy with extensive microstructural analysis, it has been shown that it is possible to develop a comprehensive picture of how some of these features influence the conductivity and to use this knowledge to improve the materials design. A number of examples to illustrate this approach will be discussed, including some recent results on the effect of Al2O3 additions to zirconia ceramics — work that began in Professor Steele’s group almost 20 years ago.