Microanalysis of clays at low temperature

Mackinnon, Ian D.R. & Kaser, Stacy A. (1987) Microanalysis of clays at low temperature. In Geiss, Roy H. (Ed.) Microbeam Analysis - 1987, San Francisco Press Inc, pp. 332-334.

Abstract

Accurate thin-film energy dispersive spectroscopic (EDS) analyses of clays with low-atomic-number (low Z) elements (e.g. Na, Al, Si), presents a challenge to the microscopist not only because of the spatial resolution required, but also because of their susceptibility to electron beam-induced radiation damange and very low X-ray count rates. Most common clays, such as kaolinite, smectite and illite occur as submicrometer crystallites with varying degrees of structural disorder in at least two directions and may have dimensions as small as one or two unit cells along the basal direction. Thus, even clays with relatively large a-b dimenstions (e.g., 100 x 100 nm) may be <5nm in the c-axis direction. For typical conditions in an analytical electron microscope (AEM), this sample thickness gives rise to very poor count rates (<200cps) and necessitates long counting times (>300s) in order to obtain satisfactory statistical precision. Unfortunately, beam damage rates for the common clays are very rapid (<10s in imaging mode) between 100kV and 200kV. With a focussed probe for elemental analyses, the damage rate is exacerbated by a high current density and may result in loss of low-Z elements during data collection and consequent loss of analytical accuracy.

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ID Code: 57742
Item Type: Conference Paper
Refereed: Yes
Keywords: clay mineralogy, kaolinite, smectite, low temperature microanalysis, electron beam irradiation
Subjects: Australian and New Zealand Standard Research Classification > EARTH SCIENCES (040000) > GEOLOGY (040300) > Mineralogy and Crystallography (040306)
Divisions: Current > Institutes > Institute for Future Environments
Copyright Owner: Copyright 1987 please consult the author
Deposited On: 11 Mar 2013 01:29
Last Modified: 11 Mar 2013 01:29

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