Mixed ionic–electronic conductors: effects of ceramic microstructure on transport properties

Recent experimental data clearly show that microstructure has a significant influence on the minor contributions to the total conductivity, following similar trends observed for the major conductivity components, in oxide semiconductors and solid-electrolyte ceramics. As for microcrystalline solid-electrolyte materials, increasing grain size in ceramics with predominant electronic transport often leads to a higher ionic conductivity. Interaction of the components in oxide composite materials may play a critical role—decreasing oxygen ionic conduction. Both ionic transport in materials with dominant electronic conductivity and electronic conduction in solid electrolytes should be analyzed not only as properties of an oxide phase, determined by the overall composition, oxygen partial pressure and charge carrier mobility, but also as functions of the ceramic microstructure—the latter becoming an increasingly important tool in the design of materials performance.