ゼオライトの分域構造と対称性

概要

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Since the early 19th century it has been recognized that many minerals including zeolites show optical phenomena which are not in harmony with the apparent symmetry of their external morphology. The phenomenon has been called optical anomaly. In low temperature aluminosilicates such as zeolites, various degrees of Al, Si ordering are produced by electron charge balance between alkali ions and Al, Si atoms on the crystal surface during growth. If Al, Si tetrahedron forms after the adsorption of alkali ions on crystal surface, the tetrahedron will be preferentially occupied with Al ion. On the other hand, if the tetrahedron forms prior to the alkali ion, it will be preferentially occupied by Si. If growth steps are inclined to mirror plane, Al. Si structure will be ordered with respect to the mirror plane, and the mirror will change into the twin plane. If the steps are normal to the mirror, the structure will be disordered, and the mirror will be maintained during growth. Therefore, zeolites consist of complicated sectors with various symmetries, and no single crystals are produced during growth.
日本粘土学会の論文
1990-04-24