Member, American Ceramic Society.
Blocking Grain Boundaries in Yttria-Doped and Undoped Ceria Ceramics of High Purity
Article first published online: 20 DEC 2004
Journal of the American Ceramic Society
Volume 86, Issue 1, pages 77–87, January 2003
How to Cite
Guo, X., Sigle, W. and Maier, J. (2003), Blocking Grain Boundaries in Yttria-Doped and Undoped Ceria Ceramics of High Purity. Journal of the American Ceramic Society, 86: 77–87. doi: 10.1111/j.1151-2916.2003.tb03281.x
E. Wachsman—contributing editor
- Issue published online: 20 DEC 2004
- Article first published online: 20 DEC 2004
- Manuscript No. 187513. Received August 20, 2001; approved August 23, 2002.
- cerium/cerium compounds;
- grain boundaries;
CeO2 samples doped with 10, 1.0, and 0.1 mol% Y2O3 and undoped CeO2 samples of high purity were studied by impedance spectroscopy at temperatures <800°C and under various oxygen partial pressures. According to microstructural investigations by SEM and analytical STEM (equipped with EDXS), the grain boundaries were free of any second phase, providing direct grain-to-grain contacts. An amorphous siliceous phase was detected at only a few triple junctions, if at all; as a result, its contribution to the grain-boundary resistance was negligible. Nevertheless, the specific grain-boundary conductivities were still 2–7 orders of magnitude lower than the bulk conductivities, depending on dopant concentration, temperature, and oxygen partial pressure. The charge carrier transport across the grain boundaries occurred only through the grain-to-grain contacts, whose properties were then determined by the space-charge layer. The space-charge potential in acceptor-doped CeO2 was positive, causing the simultaneous depletion of oxygen vacancies and accumulation of electrons in the space-charge layer. The very low grain-boundary conductivities can be accounted for by the oxygen-vacancy depletion; the accumulation of electrons became evident in weakly doped and undoped CeO2 at high temperatures and under low oxygen partial pressures.