Structural Analysis of Sepiolite by Selected Area Electron Diffraction—Relations with Physico-Chemical Properties

M. Rautureau* and C. Tchoubar
Laboratoire de Cristallographie, Université d'Orléans, et Centre de Recherche sur les Solides á Organisation Cristalline Imparfaite C.N.R.S., Orléans, France
* This work is a part of the Doctoral Thesis of M. Michel Rautureau, 1974, University of Orleans, France.
Quincunx “A disposition of five objects so placed that four occupy the corners and the fifth the center of a square or rectangle” (Oxford Universal Dictionary, 3rd Edn., revised 1955, p. 1642).

Abstract: The electron structural analysis of a Madagascar sepiolite (Ampandrandava) was carried out by selected area electron diffraction obtained from monocristals. Fourier projections, derived from the experimental intensity of Okl, hOl and hkO reflections, show that the Mg2+ cations on the edges of the sheets are distributed between two sites. Correlatively the water molecules bound to these Mg2+ occupy two distinct positions. These principal structural differences with the Brauner and Preisinger model explain details of the i.r. spectra during the desorption of water or the adsorption of polar molecules. The differences between the two models can be considered as a consequence of treating the mineral in vacuum.

Clays and Clay Minerals; February 1976 v. 24; no. 1; p. 43-49; DOI: 10.1346/CCMN.1976.0240105
© 1976, The Clay Minerals Society
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