ABSTRACT
The sintering and grain growth of ultrafine ceramic powders (particle size 10-20 nm) synthesized under hydrothermal conditions are considered. Compared to coarse (micron-sized) powders, the densification rate of compacts formed from ultrafine powders increases significantly. A problem is that the rate of the non-densifying mechanisms that lead to coarsening of the microstructure can also be significantly enhanced. The production, by sintering, of dense solids with ultrafine grain size is therefore not guaranteed. However, processing techniques such as the control of the heating schedule and the use of dopants, commonly used for microstructural control in coarse powders, are also effective for ultrafine powders. The use of these techniques is outlined for the sintering of ultrafine powders of CeO2. Bulk solids and thin films with almost full density coupled with ultrafine grain size (<200 nm) can be produced below ~1350 °C.
