Isothermal crystallization kinetics and effect of crystallinity on the optical properties of nanosized CeO2 powder

The isothermal crystallization kinetics and effect of crystallinity on the optical properties of cerium dioxide (CeO2) nanopowders synthesized using a coprecipitation route at 293 K and pH 9 were investigated using X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and ultraviolet–visible absorption spectrophotometry. The activation energy of CeO2 crystallization from dried cerium dioxide precursor powders by isothermal method of 64.1±3.24 kJ/mol was obtained. The average value of the growth morphology parameter (n) is 1.94, meaning that two-dimensional growth with plate-like morphology was the primary mechanism of CeO2 crystallization from cerium dioxide precursor powders. The indirect band gap energy (Ei) of CeO2 decreased from 3.03 eV to 2.83 eV when the crystallinity increased from 18% to 82%, and the direct band gap energy (Ed) of CeO2 also decreased from 3.76 eV to 3.64 eV.