It was recalled that this system was one of the more interesting of the fluorite oxides because its oxide ionic conductivity was higher than that of Y2O3-stabilized ZrO2 and other CeO2-based oxides. The maximization of oxide ionic conductivity in the present system was considered here. With regard to the crystallographic character of the fluorite structure, the O-vacancy level was combined with the ionic radius mismatch between host and dopant cations in order to yield criteria for fast ionic conduction. Samples of the form, SmxCe1-xO2 (where x was between 0.2 and 0.3), (Sm0.5Ca0.5)xCe1-xO2 (where x was between 0.175 and 0.3) and (Sm0.936Cs0.06Li0.004)xCe1-xO2 (where x was between 0.2 and 0.275) were prepared and characterized as examples having low, intermediate and high indices, respectively. It was found that the oxide ionic conductivity increased with increase in the effective index; thus confirming the validity of the index. The electrochemical properties of Sm0.25Ce0.75O1.88, (Sm0.5Cs0.5)0.25Ce0.75O1.84 and (Sm0.936Cs0.06Li0.004)0.25Ce0.75O1.86 were investigated at temperatures ranging from 700 to 1000C. It was noted that the oxide ionic conductivity in reducing atmospheres improved with increasing index. It was found that (Sm0.936Cs0.06Li0.004)0.25Ce0.75O1.86 had the highest-index value in the present system, and exhibited a high oxide ionic conductivity.

Application of a Crystallographic Index for Improvement of the Electrolytic Properties of the CeO2-Sm2O3 System. T.Mori, T.Ikegami, H.Yamamura: Journal of the Electrochemical Society, 1999, 146[12], 4380-5