The structure of an iron oxide cluster incorporated into zeolite Y, determined by HRTEM and SAED
The atom positions of an iron cluster (Fe6O n ) inside the framework of a zeolite (FAU, Na48(Fe2O3)38Al48Si144O384) were determined through the use of electron crystallography methods for three-dimensional reconstruction of atomic positions within the cluster from high-resolution electron micrographs and selected-area electron diffraction. The iron-containing FAU structure was determined in the space group Fd3m (a = 24.7 Å) by the use of 42 unique reflections. The Fe6O n molecule is situated in the sodalite cage with the iron atoms facing the square windows of the cage. The iron-iron distance is 3.6 Å and the distances between iron atoms and the nearest oxygen atoms in the sodalite cage are close to 2.2 Å. As a verification of the method, the same technique was used for the dermination of the structure of Na48Al48Si144O384 without iron, and the Si/Al atom positions of the zeolite framework were found to coincide with those determined from single crystal X-ray diffraction methods.
PACS61.14.-x Electron diffraction and scattering 61.14.Rq Other electron diffraction and scattering techniques for structure analysis 61.46.+w Clusters, nanoparticles, and nariocrystalline materials
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