Instability of supercritical porosity in highly doped ceria under reduced oxygen partial pressure

The thermomechanical behavior and microstructural evolution of low relative density (∼0.40) gadolinium-doped ceria are characterized under oxidative and reducing conditions at high temperatures. The electronic defects generated in the structure by Ce4+ to Ce3+ reduction play an important role on all mass diffusion phenomena, including densification and grain growth. Thermodynamically stable porosity (supercritical porosity) is dominant for isothermal sintering treatments in air. Conversely, the facilitated diffusion of ions through the lattice in reducing conditions results in a nearly full densification.