Crystal‐chemical investigation of the “cubic Al–Si spinel” issued from the thermal transformation of kaolinite and halloysite

Since its discovery in 1959 as a transient nanocrystalline product of the thermal transformation of aluminum‐rich clays, the so‐called Al–Si spinel has been the object of numerous studies aimed at determining its composition. In this work, samples obtained from fired kaolinite‐ and halloysite‐contai...

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Bibliographic Details
Published in:Journal of the American Ceramic Society Vol. 105; no. 7; pp. 4986 - 4993
Main Authors: Chauffeton, Christelle, Wallez, Gilles
Format: Journal Article
Language:English
Published: Columbus Wiley Subscription Services, Inc 01.07.2022
Wiley
Subjects:
Aluminum oxide
Al–Si spinel
Chemical Sciences
Clay
Cristallography
Crystal structure
Crystallites
Kaolinite
Material chemistry
Rietveld analysis
Silicon
Spinel
Thermal transformations
Transitional aluminas
crystal structure
Al-Si spinel
kaolinite
Rietveld analysis
ISSN:0002-7820, 1551-2916
Online Access:Get full text
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Summary:Since its discovery in 1959 as a transient nanocrystalline product of the thermal transformation of aluminum‐rich clays, the so‐called Al–Si spinel has been the object of numerous studies aimed at determining its composition. In this work, samples obtained from fired kaolinite‐ and halloysite‐containing clays were analyzed using X‐ray diffraction, leading to conclude in a single cubic (space group Fd‐3m) form, with an unvarying size of crystallites of 5 nm and a constant cell volume, typical of a transition alumina form. Trial‐and‐error Rietveld fitting procedure revealed a crystal structure consisting in an oxygen close packing and a disordered cation sublattice that differs from the known forms of spinel alumina. Rietveld quantitative phase analysis based on this model was successfully implemented on a series of fired halloysite clays, giving a first quantitative insight on the transformations in the 980–1260°C range. The resolution of the crystal structure of the “cubic Al–Si spinel” allows the first quantitative Rietveld analysis of the thermal transformation of kaolinite
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ISSN:0002-7820
1551-2916
DOI:10.1111/jace.18439