Absorption Effects in STEM Microanalysis of Ceramic Oxides

A scanning transmission electron microscope (STEM) equipped with an X‐ray energy dispersive spectrometer (EDS) was used for quantitative X‐ray tnicroanalysis of an MgO‐10 mol% NiO ceramic. Using the Cliff‐Lorimer standardless ratio technique for quantitative X‐ray microanalysis, absorption of the Mg characteristic X rays, particularly by oxygen in the specimen, was found to be a critical problem and corrections were required. This problem is characteristic of low atomic number oxide ceramics. However, preferential absorption of characteristic X rays by carbon contamination buildup during X‐ray analysis was negligible. A grain‐boundary composition profile, corrected for absorption, showed no segregation of the Ni to the grain boundary, in agreement with current segregation theory.