The specifications of the JEOL 733
electron microprobe at OSU
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The lab is currently maintained by
Dr. Elizabeth Catlos
in the School of Geology. The microprobe lab
is open to the
research community, and used by faculty and students at Oklahoma State
University for analysis of natural and synthetic materials and glasses.
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The OSU JEOL 733 is equipped with four spectrometer crystals
(LIF, PET, TAP, LDE2), back-scattered and secondary-electron scanning capability, and an energy-dispersive system consisting of a detector and
image-analysis software.
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The instrument is also capable of obtaining X-ray element maps for elemental
distributions within materials. The X-ray spectrum used in quantitative analysis
is generated by the sample in response to a finely focused electron beam
striking the surface. X-rays intensities are measured by either using
wavelength-dispersive spectrometry for quantitative data or energy-dispersive
spectrometry for qualitative mineral identification.
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Electron microprobe analysis is nondestructive and minimal sample preparation is
required. A well-polished surface is sufficient and for electrically
non-conductive surfaces, a thin carbon coat is applied to dissipate the absorbed
beam-electrons.
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Most of the periodic table can in principle be analyzed (boron through uranium),
but analytical sensitivity ranges from a low of a few parts per million for
optimum cases to several weight percent for some elements. Volume sampled is
typically a few cubic microns. Samples are prepared as flat, polished solid
mounts of ~ 1 inch diameter and must be clean and stable in a 10-5 torr vacuum
environment. Analyses quality depends on sample preparation, character of the
material, and availability of appropriate primary and secondary calibration
standards for the desired elements. The
OSU electron microprobe lab has 68 mineral standards (SPI
mounts 02758-AB, 02753-AB).
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