Structural–Transport Properties Relationships on Ce1–xLnxO2−δ System (Ln = Gd, La, Tb, Pr, Eu, Er, Yb, Nd) and Effect of Cobalt Addition

A large series of doped cerias have been \nprepared by the coprecipitation method combined with \nimpregnation and completely characterized in order to have \nan overall understanding of the structural, oxygen vacancy \nconcentration, and transport properties relationships. Several \nlanthanides were incorporated in the fluorite structure, and the \neffects of the final sintering temperature (1073 and 1573 K) \nand the addition of cobalt oxide on the structural properties \nwere studied. The chosen lanthanides (Gd, La, Tb, Pr, Eu, Er, \nYb and Nd) included a large range of ionic radii and different \nmetals exhibiting variable oxidation states under the typical \noperating conditions for these materials. The materials have been characterized by powder XRD, high-temperature XRD, micro- \nRaman spectroscopy, helium pycnometry, and dc conductivity. Transport properties were correlated with structural features \ninduced by the different ionic radii and variable oxidation state of the dopants. The highest ionic conductivity was obtained for \nthe less distorted cells (Gd- and Nd-doped ceria) which represent the optimum balance between Coulomb interactions, steric \neffects, and vacancy distribution. The lowest Ea value was found for materials with long cell parameters.