Principles of X-Ray Energy-Dispersive Spectrometry in the Analytical Electron Microscope

Williams, David B.; Goldstein, Joseph I.; Fiori, Charles E.

doi:10.1007/978-1-4899-2037-9_4

Cited by 15 publications

(8 citation statements)

References 10 publications

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“…The "In-Hole" Spectrum A classic procedure to evaluate the nature of and extent of stray radiation sources in a SEM is determination of the "in-hole" spectrum, measured by placing the beam in the blind hole of a Faraday cup, as shown schematically in Figure 5 (Williams & Goldstein, 1981). Electrons in the focused beam placed in the blind hole cannot escape after backscattering so that any contributions to the spectrum must originate from "stray" electrons scattered out of the focused beam or from X-rays created at the final aperture.…”

Section: Evaluating Generation Of Stray Radiationmentioning

confidence: 99%

Measurement of Trace Constituents by Electron-Excited X-Ray Microanalysis with Energy-Dispersive Spectrometry

Newbury

Ritchie

2016

Microsc Microanal

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Electron-excited X-ray microanalysis performed with scanning electron microscopy and energy-dispersive spectrometry (EDS) has been used to measure trace elemental constituents of complex multielement materials, where "trace" refers to constituents present at concentrations below 0.01 (mass fraction). High count spectra measured with silicon drift detector EDS were quantified using the standards/matrix correction protocol embedded in the NIST DTSA-II software engine. Robust quantitative analytical results for trace constituents were obtained from concentrations as low as 0.000500 (mass fraction), even in the presence of significant peak interferences from minor (concentration 0.01≤C≤0.1) and major (C>0.1) constituents. Limits of detection as low as 0.000200 were achieved in the absence of peak interference.

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Section: Evaluating Generation Of Stray Radiationmentioning

confidence: 99%

Measurement of Trace Constituents by Electron-Excited X-Ray Microanalysis with Energy-Dispersive Spectrometry

Newbury

Ritchie

2016

Microsc Microanal

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“…High-energy electrons hitting metal components in the illumination system produce bremsstrahlung X rays that can penetrate fixed and movable apertures. Thus, a wide X-ray beam from the electron column bathes the entire specimen and excites fluorescent X rays from regions of the specimen not under the electron probe~Williams & Goldstein, 1981;Allard & Blake, 1982!. This problem can be controlled at 100 kV by installing 1-mm-thick beam-limiting apertures in the condenser lens system, but this effect may still be a problem in AEMs operated at 200-400 kV.…”

Section: Effect Of "Hole Count" In Aemmentioning

confidence: 99%

Tutorial Review: X-ray Mapping in Electron-Beam Instruments

Friel

Lyman

2006

Microsc. Microanal.

124

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This review traces the development of X-ray mapping from its beginning 50 years ago through current analysis procedures that can reveal otherwise obscure elemental distributions and associations. X-ray mapping or compositional imaging of elemental distributions is one of the major capabilities of electron beam microanalysis because it frees the operator from the necessity of making decisions about which image features contain elements of interest. Elements in unexpected locations, or in unexpected association with other elements, may be found easily without operator bias as to where to locate the electron probe for data collection. X-ray mapping in the SEM or EPMA may be applied to bulk specimens at a spatial resolution of about 1 mm. X-ray mapping of thin specimens in the TEM or STEM may be accomplished at a spatial resolution ranging from 2 to 100 nm, depending on specimen thickness and the microscope. Although mapping has traditionally been considered a qualitative technique, recent developments demonstrate the quantitative capabilities of X-ray mapping techniques. Moreover, the long-desired ability to collect and store an entire spectrum at every pixel is now a reality, and methods for mining these data are rapidly being developed.

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“…Nevertheless, AEM/TEM techniques have limitations, in part because of spurious scattering of beams in the area of the sample (Williams et al 1989). Specimen tilting may change the spatial relations of mineral aggregates with respect to the electron beam.…”

Section: Relations Between Mixtures Of Minerals and Excess Octahedralmentioning

confidence: 99%

Chlorite Geothermometry?—Contamination and Apparent Octahedral Vacancies

Jiang

Peacor

Buseck

1994

Clays and clay miner.

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Abstract--The large contents of octahedral vacancies in published formulae of chlorite from hydrothermal systems and clastic sequences are shown to be largely caused by inclusion of other minerals. Verification is provided by analytical electron microscope (AEM) analyses of chlorite in pelitic rocks from the Gasp6 Peninsula, Quebec and the Gulf Coast, Texas. The Gasp6 chlorite occurs as discrete crystals locally coexisting with corrensite, and the Gulf Coast chlorite is free of mixed layers other than local serpentinelike 7-~ layers. Unlike most electron microprobe analyses (EMPA), but like other AEM analyses, the reported chlorite formulae do not have significant octahedral vacancies, are not Si-rich and (Fe + Mg)-poor relative to classic metamorphic chlorite, and have nearly equal amounts oftetrahedral and octahedral AI. The studied chlorites and those in metabasites and clastic rocks that could be positively identified as containing no or minimal mixed layering or submicroscopic intergrowths have little or no Ca or alkalis. In contrast, EMPA of chlorite reported for other clastic sequences show variable amounts ofNa + K + 2Ca that exhibit a poorly defined positive correlation with the proportion of octahedral vacancies. The EMPA of chlorite from the Salton Sea and Los Azufres geothermal fields that were suggested to contain temperature-dependent amounts of tetrahedral A1 (and thus used as "'chlorite geothermometers") show compositional characteristics similar to those reported for several saponite-chlorite transition series in metabasites.Continuous increases in octahedral occupancy and tetrahedral Al with increasing metamorphic grade are attributed to decreases in abundance of mixed layers or fine-grained intergrown minerals that commonly occur as a result of increasing crystal size and homogeneity in prograde sequences. Use of"chlorite geothermometry'" based on the proportion of apparent octahedral vacancies or tetrahedral A1 is therefore unwarranted and leads to inaccurate temperature estimates.

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Principles of X-Ray Energy-Dispersive Spectrometry in the Analytical Electron Microscope

Cited by 15 publications

References 10 publications

Measurement of Trace Constituents by Electron-Excited X-Ray Microanalysis with Energy-Dispersive Spectrometry

Measurement of Trace Constituents by Electron-Excited X-Ray Microanalysis with Energy-Dispersive Spectrometry

Tutorial Review: X-ray Mapping in Electron-Beam Instruments

Chlorite Geothermometry?—Contamination and Apparent Octahedral Vacancies

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