Structural transformations of Muscovite at high temperature by X-ray and neutron diffraction

• Published in: Applied clay science Vol. 38; no. 3-4; pp. 259 - 267
• Main Authors: Gridi-Bennadji, F., Beneu, B., Laval, J.P., Blanchart, P.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.02.2008; Amsterdam Elsevier Science; New York, NY Elsevier
• Subjects: Dehydroxylation; Earth sciences; Earth, ocean, space; Exact sciences and technology; Mineralogy; Muscovite; Neutron diffraction; Silicates; Structure; X-ray diffraction; X-ray diffraction; Dehydroxylation; Structure; Muscovite; Neutron diffraction; experimental studies; orientation; silica; muscovite; mica; dehydroxylation; high temperature; coordination; alumina; organization; transformations; sheet silicates; silicates; neutron diffraction; refinement; oxygen
• ISSN: 0169-1317; 1872-9053
• DOI: 10.1016/j.clay.2007.03.003

Structural transformations of Muscovite at temperature up to 1095 °C were determined using powder X-ray and neutron diffraction. Data were collected at room temperature from preliminary heated and quenched samples at 650 °C, 980 °C and 1095 °C. X-ray data were interpreted by either Rietveld method and neutron data, which complete the structural information by a better assignation of oxygen positions. With neutron data atom position was refined by fitting Pair Distribution Functions. It was found to be a progressive but continuous microstructural change, with the formation of an increasingly disorganized structure, but the layered organization of muscovite is maintained up to 1095 °C. Rietveld refinements from X-ray confirm the 6 to 5 coordination of Al atoms above 650 °C. It induces some structural changes as the orientation and mutual position of tetrahedrons in silicate layers. Pair Distribution Function refinements show the weakening of the long range structural organization, above 5 Å. At lower distance, a local order is maintained and the preferential alignments of both alumina unit pairs and silica tetrahedron were observed. This residual structural order of high-temperature muscovite is favorable to the achievement of textured ceramics.