Published online by Cambridge University Press: 11 February 2011
The effect of space charge layers in polycrystalline cerium oxide was analyzed by comparing experimental results of grain size-dependent electrical conductivity with theoretical models. Modeling included the calculation of space charge segregation of acceptor ions and of the effective electrical conductivity of polycrystalline cerium oxide in both the macroscopic and mesoscopic range of grain sizes. It is shown that an L-3 power law for the electronic conductivity in the nm-regime is characteristic for the equilibrium space charge model and different from the scaling behavior of alternative models. The origin of space charge potential was investigated by numerical calculation of the electrical potential in a two-phase model. It was found, that a positive excess charge at grain boundaries of cerium oxide is caused by an enhanced oxygen deficiency at the grain boundary core. The influence of acceptor ion doping in the dilute limit and of non-equilibrium distribution of acceptor ions on electrical conductivity was also studied.