Oxidation driven decomposition of CeNbO4 in pure oxygen

Abstract

CeNbO4 possess oxygen hyper-stoichiometry at ambient and moderate temperature. At elevated temperature CeNbO4+δ is thermally reduced to near stoichiometric CeNbO4 accompanied by a structural phase transition. Above the phase transition temperature re-oxidation of the material occurred in pure oxygen atmosphere, and in-situ X-ray diffraction revealed that CeNbO4 decomposed to CeO2 and CeNb3O9. Upon further heating CeNbO4 reappeared by a solid state reaction between CeO2 and CeNb3O9. The present findings demonstrate that CeNbO4+δ is metastable with respect to CeO2 and CeNb3O9 at low temperature.