Original paper

Structure of the {001} talc surface as seen by atomic force microscopy: comparison with X-ray and electron diffraction results

Ferrage, Eric; Seine, Grégory; Gaillot, Anne-Claire; Petit, Sabine; De Parseval, Philippe; Boudet, Alain; Lanson, Bruno; Ferret, Jocelyne; Martin, François

Abstract

The surface structure of a centimetre sized crystal of talc from the Trimouns deposit (Ariège, France) was imaged by atomic force microscopy. The direct image shows detailed characteristics of clay tetrahedral surfaces. The unit-cell dimensions obtained using atomic force microscopy (aor = 5.47 ± 0.28 and bor = 9.48 ± 0.28 Å) are found to be slightly higher, with a higher uncertainty, than those obtained using X-ray diffraction (aor = 5.288 ± 0.007 and bor = 9.159 ± 0.010 Å) and selected-area electron diffraction (aor = 5.32 ± 0.03 and bor = 9.22 ± 0.05 Å). Talc has a quasi-ideal surface, free from strong structural distortion, as compared to most other clay minerals, and is unlikely to have surface relaxation. The observation, on the obtained image, of apparent cell-dimension enlargement is then more likely attributed to instrumental artefacts, also responsible for scattered values of unit-cell parameters, rather than related to any surface structural features. The interpretation of apparent changes in unit-cell dimensions in terms of structural features for other clay minerals, in which such structural deformations is common (micas, kaolinites and chlorites), should therefore be done with extreme care.

Keywords

talcatomic-force microscopysurface structurex-ray diffractionselected-area electron diffraction