Microanalytical investigation of sintered SiC

The microstructures and compositions of Al- and B-doped pressureless sintered SiC-materials from four different sources were investigated by the combined usage of several microanalytical techniques. Besides the fundamental ceramography and chemical analysis the methods of Auger electron spectroscopy (AES), wavelength dispersive analysis of X-rays (WDX), microautoradiography and scanning transmission electron microscopy (STEM) were used. In transgranular fractured surface regions the stoichiometric Si/C relation was found by AES. The grain boundaries, however, are enriched with C and O, and also partly with B and Al. Additives and impurities are distributed in an inhomogeneous manner; the heterogeneous inclusions are very differently sized from less than 0.1 μm (STEM) to 10 to 20 μm (WDX on polished specimens) and 200 μm (AES on fracture surfaces). These results reveal the need for improving the production process. (author)