Sintering analysis of undoped and cobalt oxide doped ceria solid solutions

Pure and CoO1-x-doped Ce0.8Gd0.2O1.9 (CGO) have been analyzed with constant heating rate dilatometry. Doping changes the grain boundary structure of CGO resulting in enhanced mass transport and in increased densification rates. Significant changes in activation energies have been detected. While pure CGO exhibits a significant amount of surface diffusion, cobalt oxide doping enhances grain boundary diffusion. The obtained activation energies are 4.70 +/- 0.32 eV for CGO and 6.24 +/- 0.32 eV for CoO1-x-doped CGO. The higher activation energy of CoO1-x-doped CGO is a result of the formation of intergranular films. It is suggested that sintering of CoO1-x-doped CGO occurs by rearrangement and grain boundary diffusion whereas grain boundary and volume diffusion govern the densification of pure CGO.