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Paper No. 33-7
Presentation Time: 3:05 PM
QUANTITATIVE WDS COMPOSITIONAL MAPPING USING THE ELECTRON MICROPROBE
Quantification of pixels in X-ray intensity maps requires the same level of rigor applied in traditional point analysis. Accordingly, X-ray map quantification should include pixel-level corrections for WDS detector deadtime, corrections for changes in beam current (beam drift), changes in standard intensities (standard drift), high accuracy removal of background intensities (off-peak or mean atomic number), quantitative matrix corrections, quantitative correction of spectral interferences, and, if required, time dependent intensity corrections (for beam and/or contamination sensitive materials). The purpose of quantification at the pixel level is to eliminate misinterpretation of intensity artifacts, inherent in raw X-ray intensity signals, which distort the apparent abundance of an element. Major and minor element X-ray signals can contain significant artifacts due to absorption and fluorescence effects. Trace element X-ray signals can contain significant artifacts where phases with different average atomic number produce different X-ray continuum (bremsstrahlung) intensities, or where a spectral interference, even an apparently minor one, can produce a false-positive intensity signal. The methods we propose for rigorous pixel quantification requires calibration of X-ray intensities on the instrument using standard reference materials, as we already do for point analysis, which are then used to quantify multiple X-ray maps, and thus the relative time overhead associated with such pixel by pixel quantification is small.
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