Electrical conductivity of pure and doped nanocrystalline cerium oxide

The authors have previously shown that dense nanocrystalline CeO24 of approximately 10 nm grain size exhibits enhanced electrical conductivity ad an enthalpy of reduction that is more than 2.4 eV lower than that for conventional ceria. These effects were attributed to preferential interface reduction. In this work, the authors investigated the relationship between interfacial area, heat treatment conditions, and conductivity by varying the grain size of dense samples through annealing at various temperatures. It is shown that the conductivity does not scale in direct proportion to interfacial area. Moderate temperature (700 C) anneals which change the grain size by only a few nanometers reduce the conductivity by three orders of magnitude. It is suggested that atomistic relaxation occurs at the interfaces, and eliminates many low energy defect sites