ELECTRON CRYSTALLOGRAPHY OF ZEOLITES - STRUCTURE INFORMATION FROM HREM IMAGES AND ELECTRON-DIFFRACTION PATTERNS

High resolution electron microscope (HREM) images of zeolites have typ ically been used for crystal structure interpretation of frameworks. O nly under strict conditions (weak phase object approximation), do HREM images represent directly the projected framework potential, otherwis e the images are distorted. A large part of those distortions can be d etermined and compensated for by crystallographic image processing (CI P). This technique has been used to show that new zeolites SSZ-25 and porosil ITQ-1 are isomorphous to the MCM-22 zeolite. CIP and filtering can also be useful in HREM images of zeolite crystals doped with smal l particles, revealing directly the size and distribution of particles lying on the surface of zeolite matrix.