Compaction of ceramic powders with increasing fineness for obtaining bodies low in defects as a prerequisite for high-strength ceramics

The continuous development of high-performance ceramics and the manufacturing of more precise components require an improvement in their mechanical characteristics. This in turn leads to better use of the theoretical potential of these material properties and helps meet extraordinary high demands for reliability. The key to success here is the decrease in crystallite size and in the size of defects in the material structure. A smaller crystallite size can only be achieved by processing starting materials which have very good sintering capability and are thus very finely dispersed and which, moreover, allow the use of very low sintering temperatures and times during thermal treatment. Thus, the shaping of these finely dispersed particle systems with narrow, monomodal size distribution through uniaxial dry pressing is a technological challenge. The narrow particle size distribution lowers bulk density of the powder; it also increases the density gradients in the green bodies during shaping due to greater friction among the finer particles themselves and between the particles and the die wall in particular. This also leads to lower body density caused by the unfavourable packing conditions within the narrow, densely packed primary particles spectrum.