AN UNEXPECTED DOUBLE VALENCE CHANGE FOR CERIUM DURING THE THERMAL-DECOMPOSITION OF CEK2(NO3)(6)

Two successive changes of the oxidation state of cerium were observed when a mixed cerium potassium nitrate, CeK2(NO3)(6), was heated. The formation of a cerium (III) phase, Ce2K3(NO3)(9), together with CeO2 and KNO3, during the first stage of decomposition was clearly demonstrated by modeling the X-ray powder diffraction pattern. This cerium (III) compound decomposes into CeO, in a second stage. The processes of reduction of cerium (IV), induced by thermal decomposition, and of subsequent oxidation of cerium (III) are discussed. (C) 1995 Academic Press, Inc.