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Performing elemental microanalysis with high accuracy and high precision by scanning electron microscopy/silicon drift detector energy-dispersive X-ray spectrometry (SEM/SDD-EDS).

Newbury DE, Ritchie NW - J Mater Sci (2014)

Bottom Line: SDD-EDS throughput, resolution, and stability provide practical operating conditions for measurement of high-count spectra that form the basis for peak fitting procedures that recover the characteristic peak intensities even for elemental combination where severe peak overlaps occur, such PbS, MoS2, BaTiO3, SrWO4, and WSi2.Accurate analyses are also demonstrated for interferences involving large concentration ratios: a major constituent on a minor constituent (Ba at 0.4299 mass fraction on Ti at 0.0180) and a major constituent on a trace constituent (Ba at 0.2194 on Ce at 0.00407; Si at 0.1145 on Ta at 0.0041).Measurement of trace constituents with limits of detection below 0.001 mass fraction (1000 ppm) is possible within a practical measurement time of 500 s.

View Article: PubMed Central - PubMed

Affiliation: Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 USA.

ABSTRACT

Electron-excited X-ray microanalysis performed in the scanning electron microscope with energy-dispersive X-ray spectrometry (EDS) is a core technique for characterization of the microstructure of materials. The recent advances in EDS performance with the silicon drift detector (SDD) enable accuracy and precision equivalent to that of the high spectral resolution wavelength-dispersive spectrometer employed on the electron probe microanalyzer platform. SDD-EDS throughput, resolution, and stability provide practical operating conditions for measurement of high-count spectra that form the basis for peak fitting procedures that recover the characteristic peak intensities even for elemental combination where severe peak overlaps occur, such PbS, MoS2, BaTiO3, SrWO4, and WSi2. Accurate analyses are also demonstrated for interferences involving large concentration ratios: a major constituent on a minor constituent (Ba at 0.4299 mass fraction on Ti at 0.0180) and a major constituent on a trace constituent (Ba at 0.2194 on Ce at 0.00407; Si at 0.1145 on Ta at 0.0041). Accurate analyses of low atomic number elements, C, N, O, and F, are demonstrated. Measurement of trace constituents with limits of detection below 0.001 mass fraction (1000 ppm) is possible within a practical measurement time of 500 s.

No MeSH data available.


Related in: MedlinePlus

Comparison of the k-ratios measured simultaneously by SDD-EDS (red) and WDS (blue) in barium titantate, benitoite (Ba), and a series of Ba/Ti/Si glasses spanning a mass concentration range as high as Ba:Ti of 24:1 (Color figure online)
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Fig11: Comparison of the k-ratios measured simultaneously by SDD-EDS (red) and WDS (blue) in barium titantate, benitoite (Ba), and a series of Ba/Ti/Si glasses spanning a mass concentration range as high as Ba:Ti of 24:1 (Color figure online)

Mentions: Most of the examples reported in Table 5 involve the measurement of well-separated characteristic peaks with little overlap, with the exception of PbS, where the Pb M-family interferes with the S K-family. Performing quantitative analysis when severe overlap problems occur, such as for PbS, has traditionally required EPMA/WDS because of the superior spectral resolution of the diffractometer. This situation has now changed with the deployment of SDD-EDS because of the improved throughput and spectrum stability. The performance of SDD-EDS enables routine collection of high-count spectra, e.g., integrated counts from 0.1 keV to E0 exceeding 5 × 106 collected in 100 s or less while operating with an input count rate that produces a detector deadtime of approximately 10 %. This combination of high-count spectra with stable peak shape and position provides statistically robust peak references needed for MLLS fitting of spectral peaks to accurately extract the characteristic X-ray intensities, including situations in which severe peak overlap occurs, which are the critical input for the k-ratio protocol. Using the NIST DTSA-II EDS software engine to process spectra, it has been demonstrated that SDD-EDS can match WDS for determination of the k-ratio in severe overlap cases, such as that shown in Fig. 11 for the Ba L-family–Ti K-family interference near 4.5 keV [25]. In this study, barium titanate (BaTiO3), benitoite (BaTiSi3O9), and a series of Ba–Ti–Si–O glasses containing various Ba/Ti ratios were measured simultaneously by WDS and SDD-EDS, leading to the observation that the measured k-ratios were statistically indistinguishable, despite a Ba/Ti mass ratio as high as 24:1. Moreover, the SDD-EDS measurement was made with a factor of 3 lower dose (compared to an EPMA equipped with three WDS permitting simultaneous measurement of Ba, Ti, and Si, with the parallel measurements minimizing the WDS dose as much as possible). It is worth noting that the SDD-EDS on this instrument was mounted at a distance of 72 mm to accommodate the three WDS spectrometers that were co-mounted. In a different instrumental configuration designed to optimize the EDS measurement, the SDD-EDS could have been moved to a specimen-to-detector distance of 25 mm, gaining a factor of 10 in solid angle, thus permitting collection of the same spectra with another factor of 10 lower beam current, for an overall dose reduction of a factor of 30 compared to the EPMA with three WDS.Fig. 11


Performing elemental microanalysis with high accuracy and high precision by scanning electron microscopy/silicon drift detector energy-dispersive X-ray spectrometry (SEM/SDD-EDS).

Newbury DE, Ritchie NW - J Mater Sci (2014)

Comparison of the k-ratios measured simultaneously by SDD-EDS (red) and WDS (blue) in barium titantate, benitoite (Ba), and a series of Ba/Ti/Si glasses spanning a mass concentration range as high as Ba:Ti of 24:1 (Color figure online)
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4555346&req=5

Fig11: Comparison of the k-ratios measured simultaneously by SDD-EDS (red) and WDS (blue) in barium titantate, benitoite (Ba), and a series of Ba/Ti/Si glasses spanning a mass concentration range as high as Ba:Ti of 24:1 (Color figure online)
Mentions: Most of the examples reported in Table 5 involve the measurement of well-separated characteristic peaks with little overlap, with the exception of PbS, where the Pb M-family interferes with the S K-family. Performing quantitative analysis when severe overlap problems occur, such as for PbS, has traditionally required EPMA/WDS because of the superior spectral resolution of the diffractometer. This situation has now changed with the deployment of SDD-EDS because of the improved throughput and spectrum stability. The performance of SDD-EDS enables routine collection of high-count spectra, e.g., integrated counts from 0.1 keV to E0 exceeding 5 × 106 collected in 100 s or less while operating with an input count rate that produces a detector deadtime of approximately 10 %. This combination of high-count spectra with stable peak shape and position provides statistically robust peak references needed for MLLS fitting of spectral peaks to accurately extract the characteristic X-ray intensities, including situations in which severe peak overlap occurs, which are the critical input for the k-ratio protocol. Using the NIST DTSA-II EDS software engine to process spectra, it has been demonstrated that SDD-EDS can match WDS for determination of the k-ratio in severe overlap cases, such as that shown in Fig. 11 for the Ba L-family–Ti K-family interference near 4.5 keV [25]. In this study, barium titanate (BaTiO3), benitoite (BaTiSi3O9), and a series of Ba–Ti–Si–O glasses containing various Ba/Ti ratios were measured simultaneously by WDS and SDD-EDS, leading to the observation that the measured k-ratios were statistically indistinguishable, despite a Ba/Ti mass ratio as high as 24:1. Moreover, the SDD-EDS measurement was made with a factor of 3 lower dose (compared to an EPMA equipped with three WDS permitting simultaneous measurement of Ba, Ti, and Si, with the parallel measurements minimizing the WDS dose as much as possible). It is worth noting that the SDD-EDS on this instrument was mounted at a distance of 72 mm to accommodate the three WDS spectrometers that were co-mounted. In a different instrumental configuration designed to optimize the EDS measurement, the SDD-EDS could have been moved to a specimen-to-detector distance of 25 mm, gaining a factor of 10 in solid angle, thus permitting collection of the same spectra with another factor of 10 lower beam current, for an overall dose reduction of a factor of 30 compared to the EPMA with three WDS.Fig. 11

Bottom Line: SDD-EDS throughput, resolution, and stability provide practical operating conditions for measurement of high-count spectra that form the basis for peak fitting procedures that recover the characteristic peak intensities even for elemental combination where severe peak overlaps occur, such PbS, MoS2, BaTiO3, SrWO4, and WSi2.Accurate analyses are also demonstrated for interferences involving large concentration ratios: a major constituent on a minor constituent (Ba at 0.4299 mass fraction on Ti at 0.0180) and a major constituent on a trace constituent (Ba at 0.2194 on Ce at 0.00407; Si at 0.1145 on Ta at 0.0041).Measurement of trace constituents with limits of detection below 0.001 mass fraction (1000 ppm) is possible within a practical measurement time of 500 s.

View Article: PubMed Central - PubMed

Affiliation: Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 USA.

ABSTRACT

Electron-excited X-ray microanalysis performed in the scanning electron microscope with energy-dispersive X-ray spectrometry (EDS) is a core technique for characterization of the microstructure of materials. The recent advances in EDS performance with the silicon drift detector (SDD) enable accuracy and precision equivalent to that of the high spectral resolution wavelength-dispersive spectrometer employed on the electron probe microanalyzer platform. SDD-EDS throughput, resolution, and stability provide practical operating conditions for measurement of high-count spectra that form the basis for peak fitting procedures that recover the characteristic peak intensities even for elemental combination where severe peak overlaps occur, such PbS, MoS2, BaTiO3, SrWO4, and WSi2. Accurate analyses are also demonstrated for interferences involving large concentration ratios: a major constituent on a minor constituent (Ba at 0.4299 mass fraction on Ti at 0.0180) and a major constituent on a trace constituent (Ba at 0.2194 on Ce at 0.00407; Si at 0.1145 on Ta at 0.0041). Accurate analyses of low atomic number elements, C, N, O, and F, are demonstrated. Measurement of trace constituents with limits of detection below 0.001 mass fraction (1000 ppm) is possible within a practical measurement time of 500 s.

No MeSH data available.


Related in: MedlinePlus