Synthesis and Low-Temperature Sintering of Gd-doped CeO2 Ceramic Materials Obtained by a Coprecipitation Process

Well-dispersed ceria-gadolinia oxide powders were obtained from thoroughly isopropanol-washed coprecipitated hydroxides and oxalates, followed by a controlled drying at low temperature and calcining at 550 degrees C. The characteristics of the calcined powders and the microstructure of the green compacts were found to be of great importance in the sintering behavior. Green bodies with high agglomerate sizes need higher sintering temperatures for attaining a final density >99% D-th, while those having soft agglomerates with lower sizes were almost fully densified at a sintering temperature as low as 1250 degrees C. The densification process was studied by isothermal and constant heating rate dilatometry, and microstructural development by scanning electron microscopy. By controlling the processing variables, it was possible to obtain this low-temperature, nearly fully dense (better than 99%) sample with a homogeneous microstructure.