Electrical conductivity in rare-earth cation co-doped ceria solid-solution systems

Abstract

It is known that Sm-doped ceria shows the highest electrical conductivity among the ceria solid-solution systems with various rare-earth cation dopants. In order to clarify the ionic size effect on the oxide-ion conductivity, in the rare-earth co-doped ceria system, Ce0.8(Ln″1-xLn′x)0.2 O1.8 (Ln′ = Y, Gd and Ln″ = Nd, La), the compositional fraction (x) of the co-doped cations was determined so that the average ionic size agreed with that of Sm3+. The lattice constants of the four ceria-based compounds, which were prepared with various combinations of rare-earth dopants, agreed well with the lattice constant of the Sm-doped sample. However, the electrical conductivity decreased abruptly with increasing difference of the two cationic radii. The electrical conductivity of these co-doped materials was discussed on the basis of the local ionic arrangement in the fluorite-type structure.