PNNL

Abstract

Oxygen uptake and conductivity were measured by nuclear reaction analysis and ac impedance technique at the intermediate temperature range on sol-gel grown nanocrystalline ceria films with average grain-sizes 7 nm and 38 nm synthesized at 723 K and 1173 K, respectively. Higher oxygen uptake and lower ionic conductivity are observed in ceria films with ~7 nm grain-size. High permeation-assisted oxygen diffusion in nanocrystallites combined with oxygen trapping in the disordered region contributes in higher oxygen uptake. However the lower ionic conductivity in the film results from absence of long-range lattice ordering. Relationship between oxygen uptake and conductivity in ceria is discussed in details by considering grain-size dependent defect density, related surface area and enhanced oxygen mobility.