Improvement of electrical conductivity in fluorite related Y2O3 and fluorite CeO2 systems based on a unique effective index

Y2O3 has a crystal structure of c-type rare-earth oxide. Y2O3 does not show an oxide ionic conductivity. On the other hand, CeO2 based oxide is one of the most interesting of the fluorite oxides since the ionic conductivity o f it is higher than that of yttria-stabilized zirconia. However, CeO2 based oxides are partially reduced and develop electronic conductivity under red uced atmosphere. In this study, the effective index for the improvement of ionic conductivit y in Y2O3 and CeO2 systems was defined using ionic radii from the viewpoint of crystallography. The utility of this effective index on some electrical properties was investigated.