Functional nanoceramics for intermediate temperature solid oxide fuel cells and oxygen separation membranes

This work reviews results of research aimed at design and characterization of mixed ionic–electronic conducting perovskite–fluorite nanocomposite oxide ceramics. Nanocrystalline oxides were prepared via Pechini route, nanocomposites – via ultrasonic dispersion of their mixture in organic solvents with addition of surfactants. Genesis of the real structure of nanocomposites at sintering by conventional as well as advanced (microwave or e-beam treatment) techniques was studied in details by structural methods. Applied preparation procedures ensured nano-sizes of perovskite/fluorite domains even in dense ceramics and a high spatial uniformity of their distribution. Redistribution of elements between perovskite and fluorite domains without formation of new phases was revealed. Characterization of nanocomposite transport properties by oxygen isotope heteroexchange and conductivity or weight relaxation demonstrated that perovskite–fluorite interfaces are paths for fast oxygen diffusion. Best perovskite–fluorite combinations tested as cathode layers or dense oxygen separation layers in asymmetric supported membranes demonstrated performance promising for the practical application.