Investigation of various SiC materials by means of EPMA/WDS techniques

Abstract

The microstructure and compositions of SiC materials from different sources and processing routes were investigated by means of EPMA/WDS and image analysis techniques. The influence of various sources of errors like carbon contamination and spectrometers defocusing on the analysis has been assessed.

The presence of dissolved sintering aids, or impurities, and their distributions were investigated by EPMA/WDS. In addition, inhomogeneities, porosity agglomerations and heterogeneous inclusions were found in almost all the SiC materials, which are known to influence the corrosion and mechanical behavior of the material.

Quantification of secondary phase contents was performed by means of image analysis, EPMA and, when possible, by density measurement. All methods are affected by errors of difficult assessment. In particular, the EPMA/WDS technique has to handle the problem of non homogeneous volumes of analysis. Two quantitative approaches were attempted, both based on the averaging of many points. In the first, the beam was highly focused. In the second approach, large areas (from 10 to 50 μm in diameter) were illuminated. The errors and limits of these methods are discussed and the results compared.