An XPEEM study of structural cation distribution in swelling clays. I. Synthetic trioctahedral smectites
Résumé
X-PEEM images and XPS were collected on isolated layers of three synthetic swelling clays, one hector- ite and two saponites with various charge, recording the Si(2p), Al(2p) and Mg(2p) core level spectra from the clay sheets. Spectra were Wtted to determine the diVerent com- ponents of the core levels. Due to their large full width at half maximum, Si XPS spectra were Wtted using two to three doublets. It appears that, for a given clay mineral, Si, Al and Mg binding energies (BE) were constant, for all the observed layers. However, variations of the Si BE were observed depending on the nature of the mineral investi- gated. The various components obtained from the Wt of Si spectra could be assigned to diVerent substitution rates; binding energy shifting to lower values with substitution increase in the layer. Furthermore, variations in Si BE according to charge location were assigned to the inXuence of exchangeable cation.