New Research Trends of Fluorite-Based Oxide Materials : From Basic Chemistry & Materials Science to Engineering Applications

Fluorite-based oxide materials such as stabilised zriconias, doped cerias, and urania represent a group of the most important key engineering materials in our modern society, with their well-known various electrochemical, ceramic and nuclear etc. applications. This is primarily due to their multi-lateral excellent physical/chemical properties such as high chemical/structure stability, high oxide ion conductivity, superior mechanical strength, and unique nuclear properties, and so on. For example, urania UO2 and urania-plutonia mixed-oxide (U,Pu)O2 are almost exclusively used to represent nuclear fuels in commercial nuclear power plants throughout the world. Also in non-nuclear next-generation clean hydrogen energy technology such as solid oxide fuel cells (SOFCs), stabilised zirconias and doped cerias are the key solid electrolyes (oxide ion conductors) for their current and future more efficient versions. Stabilised zirconias, the most widely used fluorite materials, find other various practical and potential applications such as solid electrolytes for oxygen sensors/monitors/pumps, thermal barrier coatings, conventional and novel super-plastic and ultra-hard structural/refractory ceramics, high-pressure media, dielectric insulators/substrates, catalysts, synthetic teeth/jewels, etc. in non-nulcear areas and inert-matrix fuel and radioactive nuclear waste form in the nuclear area. Ceria-based systems have recently attracted increasingly more attention also as catalysts for pollution gas/liquid management and chemical substance syntheses.