Beryllium Determination in Electron Probe Microanalysis
Today a microprobe can be used to analyze light elements down to boron with dispersive monochromators. In most cases the microprobe is provided with a lead stearate multilayer analyzer for the elements between fluorine and boron. As the 2d spacing of the
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Today a microprobe can be used to analyze light elements down to boron with dispersive monochromators. In most cases the microprobe is provided with a lead stearate multilayer analyzer for the elements between fluorine and boron. As the 2d spacing of the stearate analyzer is about 100 A and is shorter than the wavelength of beryllium X-radiation (113 A), the beryllium cannot be detected. Some other multilayer analyzers having Ionger 2d spacing than that of the stearate analyzer are made of lignoceric, cerotic or melissie acid. These analyzers have been applied to long wavelength X-ray spectroscopy. However, most applications of these analyzers have been made by the fluorescense X-ray method or by procedures other than electron probe microanalysis. A large 2d spacing analyzer is built up on a mica base using the Langmuir-Blodgett technique. Lignocerate, cerotate and melissate analyzers are now available in our laboratory for the purpose of analyzing beryllium. Table 1 shows 2d spacing and detectable wavelength range and detectable element range of these analyzers. These 2d spacings are generally said to be 130 A for lignocerate, 140 A for cerotate and 160 A for melissate. The actual spacings measured with the aid of 5th order aluminium X-radiation, however, are 125, 137 and 156 A, respectively. Since the upper lirnit of 2 () of the goniometer of the JXA-5 Microprobe used in this experiment is 130°, the detectable wavelengths for the analyzers are up to 113, 124 and 141 A, respectively. Barium and lead are used as bivalent metals of the above fatty acid soap layer. The focusing spectrometer has a Johann type analyzer and a 140 mm radius of Rowland circle. The take-off angle of X-rays is 40°. The dimensions of the effective area of the multilayer analyzer are 25 mm in length and 8 mm in width. The gas flow proportional counter used is the same as a usual gas flow proportional counter in construction except for the nitrocellulose window approximately 0.2 [L in thickness. The flowing gas rnixture is 90% argon and 10% methane. The aperture of the detector is 16 mm in length and 2 mm in width. Fig. 1 shows the spectra of beryllium X-radiation from pure beryllium. In the case of the lead lignocerate analyzer, the detectable wavelength limitation is near the peak wavelength of the radiation; therefore, the perfect spectrumprofile cannot be obtained. The half widths of Table 1. Range of detectable wavelength and elements of available analyzers Analyzer
Myristate Stearate Lignocerate Cerotate Melissate
Chemical formula
M (CuHz7Üz)za M (CisHasÜz)z M (Cz4H470z)z M (CzaHsiÜz)z M (CaoHs9Üz)z
Spacing
Range of wavelength
(2d, A)
(A)
80b 100 130 140 160
17- 73 22- 91 28-117 31-126 35-144
Range of elements
K 5 B-9 F
5 B-80
4 Be-7N
4 Be-7N
4Be-6C
L
M
1701-zsMn 16s-zav 1sP-21Sc 14 Si-20 Ca 14 Si-19K
a M corresponds to bivalent cation, as Ba, Pb, etc.
b Actual spacings measured in this experiment are 79, 98, 125, 137 and 156 A for respective analyzer. 24
V. Internat. Congress on X-Ray Optics
G. Möllenstedt et al. (
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