Methods for the synthesis of large crystals of silicate zeolites

Techniques for the growth of large single crystals of zeolites are reviewed. Large is taken to mean at least 50 μm in one dimension, considerably more sizeable than the crystals commonly produced by a conventional hydrothermal crystallisation. It will be demonstrated how hydrothermal crystallisation can be modified in the laboratory, in a number of ways, to allow large crystals to be produced. These various approaches used for crystal growth will be discussed in relation to understanding hydrothermal crystallisation mechanism and also by considering briefly the occurrence of zeolites as large crystals in nature. Also reviewed are non-aqueous solvothermal and low temperature methods, such as the use of gels, for zeolite crystal growth. The discussion is focussed upon on silicate solids, and contains a review of the literature until mid 2004, including some of our own recent results.