Synthesis and properties of nanocrystalline ceria powders

Nanocrystalline CeO₂ powder was synthesized by a citrate-nitrate autoignition process and characterized by thermal analysis, x-ray diffraction, and impedance spectroscopy measurements. Nanocrystalline (20–40 nm) ceria powder with fluorite structure had formed in situ during the citrate-nitrate autoignition process. The powder prepared could be sintered to density more than 98% of theoretical density at 1450 °C. The nanocrystalline CeO₂ exhibited an increase in conductivity in Ar and H₂ than air above 600 °C, suggesting a possible electronic contribution to the conductivity at low oxygen partial pressures. Impedance measurements on the sintered samples unequivocally established the potential of this process in developing phase pure ceria compositions.