Improvement of grain-boundary conduction in gadolinia-doped ceria by the addition of CaO

This study examined the effect of CaO addition on grain-boundary conductivity in 10 mol % Gd2O3-doped CeO2 containing 500 ppm SiO2 as an impurity. The addition of CaO increased the grain-boundary conductivity similar to 50 times without affecting the grain-interior conductivity significantly. CaO was incorporated into the CeO2 lattice completely, which means that a scavenging reaction between a large CaO-related second phase and siliceous impurity was not the reason for the increased conductivity. After adding CaO, grain boundary structure changed from random to faceted. Configuration change in the grain-boundary segregation in relation to the boundary-structure variation is suggested as a possible reason. (c) 2006 The Electrochemical Society.