Sintering and electrical properties of coprecipitation prepared Ce0.8Y0.2O1.9 ceramics

Fine Ce0.8Y0.2O1.9 (YDC) powders were prepared by a chemical coprecipitatio n process. The effect of the calcination temperature on the sinterability a nd electrical conductivity of the resulting YDC ceramics was investigated. Broadening degrees of the X-ray peaks of YDC powders indicate that the crys tallite sizes of the powders significantly increase with the calcination te mperature from 500 to 1000 degrees C, which is consistent with the transmis sion electron microscopy (TEM) results. Scanning electron microscopy (SEM) photographs of the surface microstructures revealed that YDC ceramics from the powders calcined at temperatures 500-750 degrees C become highly dense (over 98% theoretical density) when sintered at 1500 degrees C, while the c eramic calcined at 1000 degrees C reached only 93% relative density. On the other hand, the average grain size of specimens obtained from powders obta ined at increasing calcination temperature decreased from 2.5 to 1 mu m, co rrespondingly. These results are attributed to the high sintering activity and grain growth rate at the same sintering condition for the finer powders calcined at lower temperature. The electrical measurement by ac impedance spectroscopy shows that the specimen from the powder calcined at 750 degree s C exhibits the highest electrical conductivity, approximately 4 Sm-1 at 7 50 degrees C in air. (C) 2000 Elsevier Science Ltd. All rights reserved.