Crystallography and X-ray diffraction in the characterization of zeolites

Zeolites is a family of crystalline solids. Zeolites are crystalline and, therefore, diffraction methods are central to attempts at atomic level structural characterization. Recently applications of diffraction techniques, X-ray diffraction, neutron diffraction and electron diffraction to zeolite structural problems are reported [۱]. The major source of structural information is X-ray crystal structure analysis. A simple criterion for distinguishing zeolites from denser inorganic materials, is based on the framework density, the number of tetrahedrally coordinated atoms per ۱۰۰۰ Å۳. A gap is clearly recognizable between zeolite and dense tetrahedral framework structures. For the known zeolites, FD values range from ۱۲.۵ to ۲۰.۲ [۲]. Crystalline zeolite molecular sieves are complex materials. As a result of structural studies during the last two decades is extensive information available on the structure of zeolites. Many of the properties of zeolites can now be interpreted on a structural basis. Thus, the zeolites can be classified by framework-structure type [۳]. Computer calculations have predicted that millions of hypothetical zeolite structures are possible. However, only ۲۳۲ of these structures have been discovered and synthesized so far, so many scientists question why only this small fraction of possibilities are observed.

کلیدواژه ها:

Powder diffraction ، Crystallography ، Zeolites ، Crystal structure