Development & Implementation of an Electron Diffraction Approach for Crystal Structure Analysis

Abstract

The application of electron diffraction to crystallographically characterize all kinds of materials has experienced new developments that have attracted some attention in recent years. A large number of structural analyses from different compounds have been already carried out with the help of 3D electron diffraction data that were not possible with the available X-ray methods. The use of a transmission electron microscope as an electron nano-diffractometer has proved to be advantageous when diffraction data from single nanocrystals are required, for instance in phase mixtures. In this way, the individual phases do not have to be purely synthesized, which always involves the risk of structural changes. The work presented here includes the development and implementation of a novel and universal routine for the accurate and reliable acquisition of electron diffraction data. The potential of this new data collection strategy to solve various crystallographic problems is illustrated using three known materials. In addition, two unknown crystal structures from commercial products are fully determined and refined; an organic dye of low symmetry and an incommensurate modulated structure of a major constituent of cement. In particular, the precise knowledge of the different crystal structures in cement clinkers, such as the alpha H -C2S, enables the exact phase analysis of these industrial phase mixtures directly from the manufacturing process, and paves the way for its CO2 emissions reduction.