Mixed valency in cerium oxide crystallographic phases: Determination of valence of the different cerium sites by the bond valence method

摘要

We have applied the bond valence method to cerium oxides to determine theoxidation states of the Ce ion at the various site symmetries of the crystals.The crystals studied include cerium dioxide and the two sesquioxides along withsome selected intermediate phases which are crystallographically wellcharacterized. Our results indicate that cerium dioxide has a mixed-valenceground state with an f-electron population on the Ce site of 0.27 while boththe A- and C-sesquioxides have a nearly pure f^1 configuration. The Ce sites inmost of the intermediate oxides have non-integral valences. Furthermore, manyof these valences are different from the values predicted from a naiveconsideration of the stoichiometric valence of the compound.