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The Kaolinite‐Mullite Reaction Series: IV, The Coordination of Aluminum
Author(s) -
BRINDLEY G. W.,
McKINSTRY H. A.
Publication year - 1961
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.1151-2916.1961.tb13714.x
Subject(s) - kaolinite , mullite , coordination number , chemistry , coordination complex , oxygen , aluminium , metal , infrared spectroscopy , crystallography , inorganic chemistry , ion , mineralogy , ceramic , organic chemistry
The AlKα emission wave length is determined by the state of coordination of Al atoms and a clear distinction can be made between Al atoms in fourfold and in sixfold coordination to oxygen and also between Al atoms in fourfold coordination to oxygen and to nitrogen. Measurements of Δ(2θ) (the difference in diffraction angle for AlKα radiations from a sample and from metallic aluminum) are used to distinguish Al in fourfold and in sixfold coordination in normal and in heat‐treated kaolin minerals. The Al atoms in meta‐kaolin are shown to have fourfold coordination to oxygen in agreement with the structure proposed by Brindley and Nakahira. After heat‐treatment at 1024°C., the coordination of Al reverts toward sixfold, and this is more marked for disordered kaolinite and halloysite than it is for well‐crystallized kaolinite and dickite. Infrared absorption measurements by Stubičan and Roy provide further confirmation of the coordination changes of the Al ions in these reactions.