INVESTIGATIONS ON VARIOUS STRUCTURAL TYPE S AND VALENCE STATES IN CERIUM CONTAINING HYDROTHERMAL SYSTEMS

By means of XRD, IR and XPS measurements, the structural types and val ence states of the products in cerium containing hydrothermal systems were investigated, The results show that, different starting species g ive different products with different stabilized valence states, such as direct formation of nanocrystalline CeO2 and a novel phase CeOHCO3, No structural transformation was found for sample CeOHCO3 after a coo l pressure treatment at 2 GPa, However, when CeOHCO3 was calcinated at high temperatures in air, high crystalline CeO2 with brown color, dif ferent from that of commercial one, was obtained.