Energy dispersion quantitative X‐ray microanalysis on a scanning electron microscope

Abstract

In this work quantitative measurements performed by EDX on SEM, abd by WDX on EPMA are compared. The commerical SEM has been improved by the addition of a beam regulation and an anticontamination device. The spectra are detected by a Si(Li) detector (FWHM = 180 eV) and digitalized by an analog‐to ‐digital converter. The spectra obtained are treated by an on‐line minicomputer PDF 11/05 included in a NS 880 system. A teminal byilt‐in magnetic tape cassette functions as a storage device for the computer. The dialogue between the system and the operator and programmation are possible through a keyboard and a visualization screen. The programs used include: spectrun smoothing, background subtaction selected area totalizing and spectrum stripping. The count rate is maintained at the order of 3000 counts per second to avoid pulse pile up and dead time losses. The experimental intensities are then corrected through a ZAF method by the profgram C ø R on an IBM 360. Binary alloys TiA1, FeA1, ZrNi, NbA1 and TiZr have been studied by K and L lines at different values of the excitation voltage. Alloys MgA1, FeMn and TiVCr Presenting overlapping peaks, and a glass, have also been analysed. The errors, advantages and limits of the method are discussed: in a homgeneous bulk material the minimum detectable limit calculated by C(DL)A = 3I B½ CA/IA is of the order of 0.03 wt % with WDX and 0.2 Wt % with EDX for 100 seconds counting time. It could be improved by increasing the counting time and by using better electronics. The precision of the result is comparable to that obtained by WDX. With EDX on SEM the rapid and simultaneous quentitative micro analysis of all the elements of 11 < Z ≤ 92 can be performed with good precision. This method is very interesting for thin targets and dispersion of precipitates.

Segregation studies in low‐alloy steels by energy‐dispersive x‐ray spectrometry

“…For elements with concentrations above about 5-10 wt % , EDS systems are capable of analytical accuracies approaching those obtained using wavelength-dispersive systems (Beaman and Solosky 1974;Dunham andWilkinson 1978, 1980;Servant et al 1975), but, at lower concentrations, both the accuracy and precision of individual analyses are limited by the poorpeak-to-background ratios of EDS spectra. It was therefore not obvious that the EDS/SEM could be successfully applied to the analysis of low-alloy steels, although Mora (1979) had shown that good accuracy could be obtained for concentrations of less than 1 .O wt % in aluminium alloys.…”

Ferrous metallurgy

“…The widest applications of microprocessors and computers with the most sophisticated software and hardware have been in emission spectrometers (124,141,142,231,312,357,406,570,576,600,694,755,756), x-ray fluorescence spectrometers (41,107,120,155,273,336,357,368,533,576,605,645,710), and electron microprobes (207,384,397,425,427,606,700).…”