SOLUTE EFFECT ON GRAIN-GROWTH IN CERIA CERAMICS

In the present work the preparation of CeO2 ceramics doped with Y2O3 (0-10 mol%) following the conventional mechanical mixing and solid state reaction of constituent oxides is described. Compositions were calcined at 1500-degrees-C for 3 h for solution formation and finely ground to maintain the average particle size at 0.5 mum in all cases. Characterization at different stages was performed for chemical composition, solid solution formation, powder particle size distribution and specific surface area. Densification behaviour was studied by high temperature dilatometry. Samples of near theoretical density were obtained by sintering at 1600-degrees-C for 6 h. Microstructural analysis showed a fine grain size (e.g. approximately 15 mum for 1.0 mol% Y2O3 compositions), having a narrow size distribution and an intergranular porosity. An inverse dependence of grain size on solute content was observed, suggesting the role of yttria as a grain growth inhibitor for the CeO2 matrix. This correlation has been explained on the basis of the currently accepted model of space charge induced grain boundary segregation of the solute ions.