Partial electronic and ionic conduction in nanocrystalline ceria: role of space charge

The total electrical conductivities of Gd-doped (0.15 mol%) and nominally pure nanocrystalline CeO2-x ceramics (similar to 30 nm grain size) were measured by impedance spectroscopy as a function of temperature and oxygen partial pressure. Careful separation of the partial ionic and electronic contributions using an electronically blocking cell allowed for a clear distinction between potential explanations. It is shown that unlike competing models the space charge model explains all the experimental features not only qualitatively but also quantitatively. (C) 2003 Elsevier Ltd. All rights reserved.