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Structural Aspects of the Lattice Thermal Expansion of Hexagonal Cordierite
Author(s) -
PREDECKI PAUL,
HAAS J.,
FABER JOHN,
HITTERMAN R. L.
Publication year - 1987
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1987.tb04954.x
Subject(s) - thermal expansion , tetrahedron , materials science , crystallography , octahedron , rietveld refinement , cordierite , neutron diffraction , crystal structure , negative thermal expansion , lattice (music) , diffraction , chemistry , composite material , physics , optics , ceramic , acoustics
The mechanism of lattice thermal expansion in pure hexagonal cordierite prepared by glass devitrification was investigated by time‐of‐flight neutron powder diffraction at temperatures from 22° to 750°C under vacuum. Full matrix least‐squares refinement of the diffraction spectra was carried out in space group P6/mcc using the Rietveld method. The structural data from the refinements were resolved into components parallel and normal to the c axis. The negative c axis expansion results from two effects: (1) increasing distortion of the T 2 tetrahedral (ring tetrahedra) with temperature, primarily due to displacement of the T 2 cations toward the c‐axis channels in the structure; (2) decreasing distortion of the T 1 /M tetrahedra/ octahedra with increasing temperature, due to octahedral I (M‐O 1 ) bond expansion and an associated decrease in torsional distortion of the T 1 tetrahedra.