XPS study on the influence of calcination conditions to cerium ion valence

For the system of Ce(NO_3 )_2·6H_2O and urea solution during homogeneous precipitation method,X-ray diffraction (XRD),infrared spectrum(IR) and especially X-ray photoelectron spectroscopy(XPS) were used to study and characterize the product structure,variety of cerium ion valence,compound surface character and kernel electronic configurations.The results of XRD and IR showed that calcination temperature had a great effect on the cerium ion valence.The products are orthorhombic Ce_2O(CO_3 )_2·H_2O with valenceⅢby using homogeneous precipitation method directly.When heated from the temperature 200℃to 250℃,the product of CeO(CO_3)_2·H_2O with valenceⅥwas finally changed into stable CeO_2 with valenceⅣ.XPS was used to study the surface character and kernel electronic configurations of the three different compounds through fine scanning of O(1s),Ce(3d) and Ce(4d) apices,and the results approved that the compounds with different valences are caused by the different valence electronic configurations of the products.