Nanocrystalline Ce0.8Gd0.2O1.9 (GDC20) powder was synthesized by ammonia co-precipitation combined with supercritical ethanol drying route, followed by characterizations with TG/DSC, XRD, BET, HR-TEM, and FESEM techniques. After calcination at 600 degrees C, the powder has a high specific surface area of 146.5 m(2) g(-1) and an average crystal size of similar to 5 nm without hard-agglomeration. The nano-GDC powder showed excellent sinterability, where by pressureless sintering at 900 degrees C for 4 h, the relative density of more than 98% and average grain size of 84 nm have been attained, which is attributed to the powder's ultrafine nanocrystal size, weak agglomeration and high homogeneity. Investigations indicate that in the initial sintering stage, grain growth behavior is mainly controlled by volume diffusion mechanism with an activation energy of similar to 5.4 eV. (C) 2009 Elsevier B.V. All rights reserved.