CHARACTERIZATION OF CERIUM OXIDES PREPARED IN WATER AND SODIUM-HYDROXIDE MIXTURES

Non-stoichiometric cerium oxides were prepared in NaOH-H2O mixtures of various compositions at room temperature from hydrated cerium(III) nitrate and cerium(IV) sulphate as precursors. The resulting products were characterized by their compositions (chemical, thermogravimetric and energy-dispersive spectrometry analysis) and by their morphology (X-ray diffraction, granulometry and electron microscopy). The compounds obtained by bubbling oxygen in cerium(III) nitrate solutions are amorphous. Their oxidation states are close to 3.8 and their average grain size is 7.6-mu-m. In contrast, those obtained from cerium(IV) sulphate solutions are better crystallized and have lower oxidation states. These compounds are formed of grains of about 9.2-mu-m.