Uniaxial viscosity of gadolinium-doped ceria determined by discontinuous sinter forging

The sintering behaviour of nanocrystalline gadolinium-doped ceria was investigated. The uniaxial viscosity determined from isothermal discontinuous sinter forging experiments. It increased dramatically during sintering from a few GPa·s at 85% to ∼120 GPa·s at 97% relative density. These values, however, are much lower than those measured for other oxide materials with submicron sizes because of much finer grain size. Since the experiments were done under isothermal conditions, it is possible to evaluate separately the effects of the relative density and the grain size. Due to grain coarsening, the effect of grain size becomes significant at high relative density, as some available models predict. It was found that Rahaman's model best fit the experimental data.