Engineering ceramics are often difficult to prepare for observation
because of their hardness, wear resistance and chemical inertness. Different
silicon nitride containing Y2O3 and Al2O3 are prepared and etched using
several different techniques and the most efficient methods are identified.
The microstructure and grain-boundary composition were examined by
electron microscopy (SEM, TEM), electron diffraction and energydispersive
X-ray microanalysis. A method has been developed to quantify
microstructure consisting of elongated, rod like -grains to discuss the
interdependence between starting materials composition, processing
condition, microstructure and resulting mechanical properties of dense Si3N4
materials. It is shown that post-sintering heat-treatment in air in the
temperature between 1100-1450 C results in substantial crystallisation of
the glassy phase.