Abstract
Diffusion of K during analytical electron microscopy (AEM) results in anomalously low count rates for this element. As the analysis area and specimen thickness decrease, count rates become disproportionally lower. Adularia and muscovite show different diffusion profiles during AEM; for muscovite a strong dependence of diffusion on crystallographic orientation has been observed. Conditions giving rise to reliable chemical data by AEM are the use of a wide scanning area (>800 × 800 Å) and/or large beam size to reduce the effect of diffusion of alkali elements, a specimen thickness greater than about 1000 Å, constant instrument operating conditions, and the use of a homogeneous, well-characterized standard sample. The optimum thickness range was obtained by determining the element intensity ratio vs. thickness curve for given operating conditions. The standard and unknown should have a similar crystal structure and, especially for strongly anisotropic minerals such as phyllosilicates, a similar crystallographic orientation with respect to the electron beam.
Similar content being viewed by others
References
Ahn, J. H. and Peacor, D. R. (1986) Transmission and analytical electron microscopy of the smectite-to-illite tran-sition: Clays & Clay Minerals 34, 165–179.
Ahn, J. H., Peacor, D. R., and Essene, E. J. (1986) Cation-diffusion-induced characteristic beam damage in transmission electron microscope images of micas: Ultramicroscopy 19, 375–382.
Allard, L. F. and Blake, D. F. (1982) The practice of modifying an analytical electron microscope to produce clean X-ray spectra: in Microbeam Analysis—1982, K. F. J. Heinrich, ed., San Francisco Press, San Francisco, 8–19.
Blake, D. F., Allard, L. F., Peacor, D. R., and Bigelow, W. C. (1980) “Ultraclean” X-ray spectra in the JEOL JEM-100CX: in Proc. 38th Ann. Meeting, Electron Microsc. Soc. Amer., San Francisco, 1980, G. W. Bailey, ed., Claitor’s Publishing Division, Baton Rouge, Louisiana, 136–137.
Cliff, G. and Lorimer, G. W. (1975) The quantitative analysis of thin specimens: J. Microsc. 103, 203–207.
Craw, D. (1981) Oxidation and microprobe-induced potassium mobility in iron-bearing phyllosilicates from the Ota-go schists, New Zealand: Lithos 14, 49–57.
Goldstein, J. L., Costley, J. L., Lorimer, G. W., and Reed, S. J. B. (1977) Quantitative X-ray analysis in the electron microscope: in SEM 1977, O. Johari, ed., IIT Research Inst., Chicago, 315–324.
Isaacs, A. M., Brown, P. E., Valley, J. W., Essene, E. J., and Peacor, D. R. (1981) An analytical electron microscopy study of a pyroxene-amphibole intergrowth: Contrib. Mineral. Petrol. 77, 115–120.
Knipe, R. J. (1979) Chemical analysis during slaty cleavage development: Bull. Mineral. 102, 206–210.
Lee, J. H., Peacor, D. R., Lewis, D. D., and Wintsch, R. P. (1986) Evidence for syntectonic crystallization for the mudstone-to-slate transition at Lehigh Gap, Pennsylvania, U.S.A.: J. Struct. Geol. 8, 767–780.
Lorimer, G. W. (1987) Quantitative X-ray microanalysis of thin specimens in the transmission electron microscope: A review: Mineral. Mag. 51, 49–60.
Lorimer, G. W. and Cliff, G. (1976) Analytical electron microscopy of minerals: in Electron Microscopy in Mineralogy, H.-R. Wenk, ed., Springer-Verlag, Berlin, 506–519.
Veblen, D. R. and Buseck, P. R. (1980) Microstructure and reaction mechanism in biopyriboles: Amer. Mineral. 65, 599–623.
White, S. H. and Johnston, D. C. (1981) A microstructural and microchemical study of cleavage lamellae in a slate: J. Struct. Geol. 3, 279–290.
White, S. H. and Knipe, R. J. (1978) Microstructure and cleavage development in selected slates: Contrib. Mineral. Petrol. 66, 165–174.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
van der Pluijm, B.A., Lee, J.H. & Peacor, D.R. Analytical Electron Microscopy and the Problem of Potassium Diffusion. Clays Clay Miner. 36, 498–504 (1988). https://doi.org/10.1346/CCMN.1988.0360603
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1346/CCMN.1988.0360603