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

The microstructure of polymer-derived Si-based ceramic materials was c haracterised with elemental distribution images produced by electron s pectroscopic imaging. Depending on the processing conditions, a variet y of different microstructures were obtained from the same precursor. without sintering additives, amorphous silicon carbonitride which is s table against crystallisation lip to 1400 degrees C is formed In the p resence 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 c omprising nano-sized SiC inclusions in the Si3N4 grains. The developme nt of the microstructure of the Si3N4/SiC composite materials was inve stigated as a function of the sintering temperature and of the concent ration of the sintering additives. The observed microstructural change s lead to conclusions on the processes which occur curing the sinterin g of the materials.