Electric Properties Change during Morphological Evolution of CeO 2 Nanostructures: Synergy between Bulk and Surface Defects

CeO2 samples were synthesized via the polymeric precursor method at different calcination temperatures. Electric properties were investigated using positron annihilation lifetime spectroscopy, electron paramagnetic resonance spectroscopy, and complex impedance spectroscopy. Reduction in the specific surface area of the particles with increasing calcination temperature along with morphological changes were observed. PALS depicted doubly-ionized oxygen vacancies surrounded by two Ce3+ atoms, while the EPR spectroscopy showed a singly-ionized oxygen vacancy surrounded by Ce3+ and Ce4+ ions. Impedance measurements unraveled the presence of polarons, while thermal treatments led to a lower electrical conductance, as the calcination temperature increased.