Quantification Curves for XRD Analysis of Mixed-Layer 14Å/10Å Clay Minerals

C. H. Pons1, C. de la Calle2 and J. L. Martin de Vidales3
1 Université d'Orléans, CRMD Unité Mixte CNRS-Université, U.F.R. Faculté des Sciences Rue de Chartres BP 6759, 45067 Orléans Cedex 2, France
2 Instituto de Ciencia de Materiales, Sede D, C.S.I.C., c) Serrano 113 28006 Madrid, Spain
3 Departamento de Quimica Agricola, Facultad de Ciencias Universidad Autonoma de Madrid, 28049 Madrid, Spain

Abstract: Using theoretical profiles of diffracted X-ray intensity for interstratification between layers having d-spacings around 14.3 Å and 10.1 Å, a series of diagrams was derived from which the proportion of 14.3 Å layers (W14) and the probability of passing from a 14.3 Å layer to a 10.1 Å layer (P14/10) can be derived. W14 can be derived independently of P14/10 using the angular distance between reflections situated at 18.2° and 25.4° 2θ (CuKα). Once W14 is determined, P14/10 may be obtained using the angular width of the diffuse reflections between 27° and 34° 2θ. In this case, two different diagrams are proposed for P14/10 determination because experimental X-ray patterns show either one or two diffuse reflections. Comparison of five experimental patterns with theoretical patterns calculated using W14 and P14/10 obtained using these diagrams indicates that the method can be useful for determining W14 and P14/10 in unknown samples. Moreover, the method described is independent of the Lorentz polarization factor and the layer type. The d-spacings associated with the two kinds of layers, however, should be similar (± 1%) to those for which the determinative diagrams were calculated.

Key Words: Biotite • Chlorite • Interstratification • Mixed-layer quantification • Vermiculite

Clays and Clay Minerals; April 1995 v. 43; no. 2; p. 246-254; DOI: 10.1346/CCMN.1995.0430212
© 1995, The Clay Minerals Society
Clay Minerals Society (www.clays.org)