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NOTES ON THE X‐RAY DIFFRACTION PATTERNS OF MULLITE *
Author(s) -
Posnjak E.,
Greig J. W.
Publication year - 1933
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.1151-2916.1933.tb16936.x
Subject(s) - mullite , diffraction , powder diffraction , materials science , mineralogy , orientation (vector space) , x ray crystallography , crystallography , geology , optics , composite material , chemistry , geometry , physics , mathematics , ceramic
A wide range of artificial alumina‐silica products has been examined by the X‐ray powder method. In each case in which the pattern has been sufficiently clear to permit a decision the pattern has been that of mullite, not that of sillimanite. The examination included a number of preparations made by heating clay minerals and clays at 1000°. Mullite crystals containing alumina or the oxides of iron or titanium in solid solution give diffraction patterns in which the lines are slightly displaced toward the origin with respect to the corresponding lines in the diffraction pattern of the standard mullite (3Al 2 O 3 .2SiO 2 ). Mullite crystals, freed by HF treatment from the matrix in which they grew, often give diffraction patterns in which the intensities of certain lines arc strikingly different from normal. This is due to the orientation of the minute elongated crystals when mounted for photographing. Finally, two recent papers proposing special names for certain similar materials are discussed and, on the basis of published data and the evidence presented here, these proposals are found to be unwarranted.