Low temperature processing of dense nanocrystalline yttrium-doped cerium oxide ceramics

Nanocrystalline cerium oxide ceramics of high homogeneity and nearly full density were prepared. The starting material was synthesized by the direct homogeneous precipitation method using hexamethylenetetramine (HMT). Two alternative routes for consolidation into green bodies were employed: (i) centrifugal casting of an electrostatically stabilized colloidal solution and (ii) cold isostatic pressing of dried ceria powder. The green bodies were sintered at temperatures between 700 and 1000degreesC. The sinter activities of both nanocrystalline materials were strongly enhanced if compared to microcrystalline ceria. Green bodies, which were generated by colloidal processing exhibited the highest sinter activities, associated with a unique pore structure. The effect of yttrium doping on the grain size after sintering at high temperatures was also investigated. The combination of yttrium doping and colloidal processing allowed for the synthesis of dense nanocrystalline cerium oxide ceramics by pressureless sintering. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.