The effect of forming stresses on the sintering of ultra-fine Ce0.9Gd0.1O2−δ powders

The effect of particle and pore arrangement on sintering and densification of ultra-fine (∼130 nm) Ce0.9Gd0.1O2−δ powder was evaluated. The common understanding that higher initial density of a ceramic network leads to a higher sintered density is not valid for fine powders, which have extremely good sinterability when there is a favourable particle packing. The effect of the applied stresses during forming (which produce different particle packing arrangements) was investigated by forging green bodies by different shaping techniques, including casting, and cold isostatic pressing. Samples formed with techniques that apply low levels of stress had a particle arrangement which significantly enhanced sintering at low temperature, compared to those prepared by high stress techniques. The sample geometry, heat treatment for organic removal and the initial density of the green body had a negligible effect on the final density when the ratio of the pore size to particle size was around 1.