X-ray Spectrometry

X-ray spectrometry is one of the most common techniques implemented in SEM for microanalysis. Energy Dispersive X-ray Spectroscopy (EDX) and Wavelength Dispersive X-ray Spectroscopy (WDX) are two of these techniques in which characteristic X-rays generated from the electron beam-sample interaction are analysed to provide elemental composition of the sample in the form of spectra (histograms) in which individual elements can be identified. Peaks in the EDX and WDX spectra correspond to characteristic X-rays lines from a specific element. Thus, the spectra provide quantitative chemical characterisation of the samples.
In an EDX analysis, the whole range of energies of the characteristic X-rays is simultaneously measured as opposed to WDX in which only a single wavelength (corresponding to one energy value) is measured at a time. Therefore, EDX analysis is faster compared to WDX.

In terms of energy resolution, WDX offers significantly better resolution than EDX. Peaks absent in an EDX analysis are clearly resolved in a WDX spectrum. This is especially useful when analysing trace elements.

EDX and WDX data can simultaneously.be collected without compromising either technique. For unknown samples, it is convenient to perform an initial EDX analysis that will identify the main elements present in the sample, followed by a more sensitive WDX analysis in order to resolve overlapping peaks and detect trace elements that beyond the detection limit of the EDX detector.

In order to best fit your particular analytical needs, a variety of third-party spectrometers can be integrated into TESCAN SEM and FIB-SEM systems.
X-ray Spectrometry
EDX map of structure with carbides

Related Application Notes

Analysis of Self-Compacting Concrete
SEM helps scientists and technologists study different kinds of morphological changes in materials during their compaction such as ettringite formation. Practical information on the chemical composition of concrete as well as phases created during dehydration processes can be investigated with a SEM system equipped with an energy dispersive spectrometer (EDS). The available low vacuum mode allows the study of sample of concrete in their natural state without the need of coating the sample, thus eliminating possible sources of interference in analysis.
pdf – 2.6 MB
SEM in the Cement Industry
A scanning electron microscope (SEM), equipped with an energy dispersive X-ray (EDS) detector, is an effective instrument for in-depth analysis of various materials. The combination of SEM with EDS microanalysis is particularly used in the construction industry for quality control and verification of material composition. Samples of cement and cement additives (powdered gypsum and fly ash), from Israel’s sole cement producer, were examined by using the powerful VEGA3 SEM with a lanthanum hexaboride (LaB6) electron source. Compared to a heated tungsten (W) filament, LaB6 provides higher resolution and brightness and longer lifetime. The chemical composition of a fly ash particle and the element distribution over the sample surface was determined by EDS.
pdf – 1.6 MB