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

Fine Ce0.8Y0.2O1.9 (YDC) powders were prepared by a chemical coprecipitation process. The effect of the calcination temperature on the sinterability and electrical conductivity of the resulting YDC ceramics was investigated. Broadening degrees of the X-ray peaks of YDC powders indicate that the crystallite sizes of the powders significantly increase with the calcination temperature from 500 to 1000 degrees C, which is consistent with the transmission 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 ceramic calcined at 1000 degrees C reached only 93% relative density. On the other hand, the average grain size of specimens obtained from powders obtained at increasing calcination temperature decreased from 2.5 to 1 mu m, correspondingly. 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 degrees C exhibits the highest electrical conductivity, approximately 4 Sm-1 at 750 degrees C in air. (C) 2000 Elsevier Science Ltd. All rights reserved.