Influence of porosity on densification and grain growth kinetics of Ce_0.9Gd_0.1O_1.95 tape

Gadolinium doped-ceria (CGO) is an important material that offers high stability, tolerance against harsh environments and high ionic and electronic conductivity at high temperatures. For most of its applications, CGO is applied as a thin dense layer on a porous support structure. However, highly porous layer allowing gas flow is necessary in catalytic and in gas purification devices. During the sintering with shrinkage, the total solid volume is maintained to be a constant value but the shape and size of each particle change with the formation of grain boundaries. This change in solid particles is accompanied by the change of shape, size and fraction of pores in a given volume. Therefore, porosity can be treated as an extra phase during sintering study. In this work, we presented the densification and grain growth behaviour of Ce_0.9Gd_0.1O_1.95 tape cast layers with different percentage of porosity. The emphasis was put on the effect of porosity on densification and grain growth kinetics. Derived from the sintering constitutive laws, the densification and grain growth kinetics were experimentally characterized and analyzed. Furthermore, the activation energies for viscous flow were determined from master viscosity curves, which are comparable to the kinetic values obtained from densification and grain growth. It is indicated that porosity has negligible effect on densification kinetics, but high porosity decreases the chance of particle contact, and grain boundary mobility is therefore slowed, which leads to slower grain growth.