Study of structural defects in zeolites by high-resolution electron microscopy and Fourier analysis methods

For thin crystals and weak-phase objects, the phase grating approximation indicates that intensities are directly proportional to the projected lattice potencial VZ (x, y). Additionnally at the optimum focus condition, i. e. γ = π/2 (see ref. (2) for details) both electron diffraction and optical transform patterns are identical. Therefore, for very thin crystals, i.e. t < 102A, and several types of zeolites, including ZSM-5, Faujasites X, Y, erionites and A-type zeolites, the main assumptions of the phase grating approximation hold, making possible a complete study of structural features taking place at a nearly atomic scale. The method used to characterize the ultraestrncture of those zeolites are high resolution electron microscopy, Fourier analysis in the computer of the digitized micrographs and Laser optical diffractometry.