Disorder and Defect Scattering, Thermal Diffuse Scattering, Amorphous Material

Abstract

Abstract Most properties and virtually all transformations in solids are strongly influenced by defects. Hence the characterization of defect structures has been a challenge to structure research ever since models of various crystalline defects were advanced in the 1930s. Optical microscopy, spectroscopy and in particular x-ray diffraction contributed significantly to insight in the nature of defects, notably the statistical description of short range order and the relation of crystal structures to transformations. But it was through the application of electron microscopy techniques, at first by diffraction contrast imaging and selected area diffraction in the 1950s and 60s, that we were able to construct the present detailed and many-faceted picture of defects in inorganic solid matter: of dislocation configurations, of the nature and distribution of planar faults and of relations between short range and long range ordering in a variety of compounds. Schematic models and statistical pictures based on more circumstantial evidence could be confirmed, replaced or augmented by direct observations of defect arrangements and by diffraction information about local structure within individual crystal grains and precipitates. A further wealth of detail was offered in the 1970s by high resolution imaging of the projected atomic arrangement. The investigation of local structure - as distinct from the average structure normally studied with x-ray or neutron diffraction - became a prime domain of electron microscopy techniques.