POLYMER-DERIVED SI-BASED BULK CERAMICS .2. MICROSTRUCTURAL CHARACTERIZATION BY ELECTRON SPECTROSCOPIC IMAGING

The microstructure of polymer-derived Si-based ceramic materials was characterised with elemental distribution images produced by electron spectroscopic imaging. Depending on the processing conditions, a variety of different microstructures were obtained from the same precursor. without sintering additives, amorphous silicon carbonitride which is stable against crystallisation lip to 1400 degrees C is formed In the presence of Al2O3 and Y2O3 as sintering additives, Si3N4/SiC-composite materials and Si2N2O ceramics ape produced. Sintering a mixture of Si(3)N4 powder with additional polysilane leads to a Si3N4SiC-composite comprising nano-sized SiC inclusions in the Si3N4 grains. The development of the microstructure of the Si3N4/SiC composite materials was investigated as a function of the sintering temperature and of the concentration of the sintering additives. The observed microstructural changes lead to conclusions on the processes which occur curing the sintering of the materials.