Hostname: page-component-77c89778f8-5wvtr Total loading time: 0 Render date: 2024-07-18T04:17:40.787Z Has data issue: false hasContentIssue false

Analytical Electron Microscopy in Clays and Other Phyllosilicates: Loss of Elements from a 90-nm Stationary Beam of 300-keV Electrons

Published online by Cambridge University Press:  28 February 2024

Chi Ma*
Cooperative Research Center for Landscape Evolution and Mineral Exploration, Department of Geology, Australian National University, Canberra, ACT 0200, Australia
John D. FitzGerald
Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
Richard A. Eggleton
Cooperative Research Center for Landscape Evolution and Mineral Exploration, Department of Geology, Australian National University, Canberra, ACT 0200, Australia
David J. Llewellyn
Electron Microscopy Unit, Australian National University, Canberra, ACT 0200, Australia
Plesent adress: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125.


Diffusion of alkali and low-atomic-number elements during the microbeam analysis of some silicates by analytical electron microscopy (AEM) has been known for some time. Our repeated analyses at 300 kV of kaolinite, halloysite, smectite, biotite, muscovite and pyrophyllite, however, showed differential loss (relative to Si) of not only alkali elements (such as K, Na, Mg) and low-atomic-number elements (such as Al) but also higher-atomic-number elements (such as Fe, Ti). For AEM of these phyllosilicates, a Philips EM430/EDAX facility with a tungsten filament was used to provide a current of 0.3 nA in a stationary beam of nominal diameter 90 nm. The loss of Al in kaolin minerals during analysis is particularly severe. Kaolin crystals can be damaged by the electron irradiation over several seconds, making it the most sensitive clay to the electron beam; in general, relative phyllosilicate stabilities are kaolin < smectite < pyrophyllite < mica. A clear dependence of element loss on crystallographic orientation has been observed for layer silicates in our study; a greater element loss occurred when the plane of the specimen foil was perpendicular to the basal planes of the phyllosilicate crystals than when the foil was parallel to the basal planes. Lower beam current, larger beam diameter and thicker specimens all reduce the loss of elements. The initial stage of irradiation produces highest rates of element loss and the rate of loss can be fitted by an exponential decay law. The analyses at low temperature of phyllosilicates showed that element loss remains serious in our analytical conditions. Since the element loss appears to be instrument- and method-dependent, one should use closely related, well-characterized phyllosilicates as compositional standards to calibrate any AEM instrument that is to be used to analyze unknown phyllosilicates, and the standards and unknowns should be analyzed under identical conditions.

Research Article
Copyright © 1998, The Clay Minerals Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


Ahn, J.H. Peacor, P.R. and Essene, E.J., 1986 Cation-diffusion-induced characteristic beam damage in transmission electron microscope images of micas Ultramicroscopy 19 375382 10.1016/0304-3991(86)90097-5.CrossRefGoogle Scholar
Cliff, G. and Lorimer, G.W., 1975 The quantitative analysis of thin specimens J of Microscopy 103 203207 10.1111/j.1365-2818.1975.tb03895.x.CrossRefGoogle Scholar
Knipe, R.J., 1979 Chemical analysis during slaty cleavage development Bull Mineral 102 206210.Google Scholar
Lorimer, G.W. Cliff, G. and Wenk, H.R., 1976 Analytical electron microscopy of minerals Electron microscopy in mineralogy Berlin Springer 506519 10.1007/978-3-642-66196-9_38.CrossRefGoogle Scholar
Ma, C., 1996 The ultra-structure of kaolin [Ph.D. thesis] Canberra, Australia Australian Nat Univ.Google Scholar
Ma, C. Eggleton, R.A., Pain, C.P. Craig, M.A. and Campbell, I.D., 1994 Structural characteristics of kaolin minerals from eastern Australian regolith Abs Australian Regolith Conf .Google Scholar
Mackinnon, I.D.R., Mackinnon, I.D.R. and Mumpton, F.A., 1990 Low-temperature analyses in the analytical electron microscope Electron-optical methods in clay science Boulder, CO Clay Miner Soc 90106.CrossRefGoogle Scholar
Mackinnon, I.D.R. Kaser, S.A. and Geiss, R.H., 1987 Microanalysis of clays at low temperature Microbeam Analysis 332333.Google Scholar
Peacor, D.R. and Buseck, P.R., 1992 Analytical electron microscopy: X-ray analysis Minerals and reactions at the atomic scale: Transmission electron microscopy Washington, DC Miner Soc Am 113140 10.1515/9781501509735-008.CrossRefGoogle Scholar
Robertson, I.D.M. and Eggleton, R.A., 1991 Weathering of granitic muscovite to kaolinite and halloysite and of plagioclase-derived kaolinite to halloysite Clays Clay Miner 39 113126 10.1346/CCMN.1991.0390201.CrossRefGoogle Scholar
van der Pluijm, B.A. Lee, J.H. and Peacor, D.R., 1988 Analytical electron microscopy and the problem of potassium diffusion Clays Clay Miner 36 498504 10.1346/CCMN.1988.0360603.CrossRefGoogle Scholar
Williams, D.B. and Carter, C.B., 1996 Transmission electron microscopy: A textbook for materials science 10.1007/978-1-4757-2519-3.CrossRefGoogle Scholar