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WDS Qualitative Analyses

Often when characterizing materials simply understanding the chemical constituents present within the material is critical. EPMA is one of the quickest and most accurate methods by which to determine the elements present within a solid material. Qualitative analyses are done by driving the WDS spectrometers over a predetermined wavelength range (specific elements can be targeted, or entire range of spectrometer can be covered) while bombarding the material with a high energy beam of electrons. Elements present within the materials will display higher X-ray counts than the background and will present themselves as distinct peaks on the spectrum (see figure below). WDS spectra can be collected on five spectrometers simultaneously allowing for the rapid characterization of elements in an unknown material. Commonly in materials characterization similar datasets are collected using energy-dispersive spectrometers (EDS). WDS differs from EDS in that WDS spectrometers have greater than an order-of-magnitude better spectral resolution allowing for energy peaks that typically overlap when analyzing using EDS to be clearly resolved. Common applications include identifying minerals, glasses, and various types of metal alloys to characterizing and identifying particles during failure analyses.

Chart
WDS spectrum illustrates the clear distinction between the Mn Ka and Cr Kb intensity peaks in a stainless steel sample