Enhancement of grain-boundary conduction in gadolinia-doped ceria by the scavenging of highly resistive siliceous phase

This paper proposes MgO as a new scavenger material that can mitigate the harmful effects Of SiO2 impurity on the grain-boundary conduction in 10 mol.% gadolinia-doped ceria (GDC). The addition of 0.3-10 mol.% of MgO resulted in an up to similar to 45-fold increase in the grain-boundary conduction of a GDC specimen containing 500 ppm Of SiO2 impurity. The solubility limit of MgO in GDC was found to be as low as similar to 0.1 mol.% and most of the MgO existed as a second phase. Electron energy-loss spectroscopic analysis indicated the formation of forsterite (MgSiO4), due to a reaction between MgO and the siliceous intergranular phase, to be the scavenging mechanism. (c) 2007 Acta Materialia, Inc. Published by Elsevier Ltd. All rights reserved.