IR studies of cerium dioxide: influence of impurities and defects

An infrared study of CeO2 is presented which allows discrimination of the bands due to residual carbonaceous impurities from the bands arising from multiphonon absorption and electronic transitions induced by atomic defects. CO adsorption experiments show the presence of coordinatively unsaturated (cus) Ce3+ or Ce4+ surface ions depending on the nature of the pretreatment. The role of plasmon–phonon coupling in the infrared examination of semiconductors is also stressed.