%0 Journal Article
%A Sánchez del Río, Manuel
%A García Romero, Emilia
%A Súarez Barrios, Mercedes
%A Silva, Iván da
%A Fuentes Montero, Luis
%A Martínez Críado, Gema
%T Variability in sepiolite: Diffraction studies
%D 2011
%@ 0003-004X
%U https://hdl.handle.net/20.500.14352/43840
%X Twenty sepiolites of known composition from different origins were analyzed to quantify thevariability in structural parameters and its possible relationships with composition and morphology.Morphology SEM analyses led to classify the sepiolites into several groups, beyond the two simplemacroscopic or clay groups. X-ray powder diffraction with synchrotron light was used to discuss thevariability of the a and b cell parameters with the nature of the cations and occupancy of the octahedralshell. Rietveld refinement using the ideal sepiolite model is performed on sepiolites at two temperatures:225 °C (for zeolitically dehydrated sepiolite) and 25 °C (for hydrated ambient sepiolite). Thelatter permitted to locate ca. six molecules of the zeolitic H2O within the tunnels.A few samples were selected to evaluate the feasibility and potential of single-crystal diffractionmethods: X-ray microdiffraction and electron diffraction. The macroscopic sepiolites gave wellstructuredand rich X-ray fiber diffraction patterns, in excellent agreement with ab initio simulations.High-quality single-crystal electron diffraction patterns for three axis zones are indexed and comparedwith simulations. The experimental and modeling results for X-ray microdiffraction and electron diffractionopen a new path for quantitative crystallography on sepiolite and other fibrous clays fromthe sepiolite-palygorskite group.
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