Modification of space charge transport in nanocrystalline cerium oxide by heterogeneous doping

[摘要] (cont.) After annealing either with or without a diffusion source at temperatures of 700-8000C, both the ionic and electronic partial conductivities decreased. The ionic transferene numbers with and without a diffusion source were 0.26 and 0.76, respectively. Based on the existing framework of charge transport in polycrystalline materials, carrier profiles associated with the Mott-Schottky and Gouy-Chapman models were integrated in order to predict conductivity values based on parameters such as grain size and the space charge potential. Mott-Schottky profiles with a space charge potential of 0.44V were used to describe the behavior of the ceria thin films in the as-deposited state. It is proposed that annealing at temperatures of 700TC and above resulted in segregation of acceptor impurity ions to the grain boundary, resulting in GouyChapman conditions. The best fit to the annealed data occurred for a space charge potential of 0.35 V: a decrease of approximately 90 mV from the as-deposited state. In addition, a high-conductivity interfacial layer between the CeO2 and substrate was detected and was determined to influence samples with no surface diffusion source to a greater degree than those with NiO or Gd203.

[发布机构] Massachusetts Institute of Technology