Kinematical diffraction by distorted crystals – dislocation X-ray line broadening

Abstract

The current state of the description and evaluation of dislocation-induced X-ray diffraction line broadening has been reviewed. The diffraction-line broadening can be analyzed in terms of line width, moments or Fourier coefficients. However, in the last years, whole pattern fitting has become the most popular method of evaluation. The line width is proportional to the Burgers vector of dislocations, to the square-root of dislocation density and to the so-called orientation (contrast) factor. The orientation factor determines the hkl dependence of broadening and is a function of the elastic characteristics of the material investigated and the orientation of the diffraction vector with respect to the Burgers vector and dislocation line. Since a completely random dislocation distribution of dislocations is impossible, another parameter connected to the dislocation correlation (cut-off radius) must be included in the description. The theory of dislocation-induced line broadening has been developed many years ago, but it is still not completely satisfactory from the point of view of its practical application to line profile analysis. General problems of present line profile analysis on samples with dislocations are mentioned. This includes consideration of the 2 nd kind stresses, texture and sample inhomogeneities.

Functional Fatigue and Tension–Compression Asymmetry in [001]-Oriented Co49Ni21Ga30 High-Temperature Shape Memory Alloy Single Crystals

“…7a it can be deduced that fatigue leads to an increase of those deviations. This effect can be attributed to residual stresses between different domains as well as between the martensite and the strained austenite component in the sample [37]. In x-direction peak broadening of fatigued austenite cannot be resolved.…”

A Comparative Study of Dislocations in HVPE GaN Layers by High-Resolution X-Ray Diffraction and Selective Wet Etching

“…As it was noted in [1,2] for the bulk GaN samples, the shape of the pits depends on the polarity of the etched surface. The pits are hexagonal on Ga-polar and circular on N-polar basal surface.…”

“…The twist and tilt angles derived from the plots have been substituted into (1) and (2) to calculate screw and edge components of the dislocation density. The volume-weighted correlation length has been determined along with the angles from the extrapolated plot intercept with the ordinate axis.…”

“…Therefore the XRD can be considered as the preferred metrology technique for monitoring of product substrates. Despite a number of the XRD methods developed for evaluation of the dislocation density [1], they are far from having reached conclusive results from a metrological point of view. Recently developed selective wet etching of the dislocations in bulk GaN has been confirmed to show the strict correspondence between the etch pits density (EPD) and the dislocation density measured by transmission electron microscopy (TEM) [2].…”

Correlating Microstrain and Activated Slip Systems with Mechanical Properties within Rotary Swaged WNiCo Pseudoalloy

“…It is given by the anisotropic characters of the displacement fields of dislocations (line defects), which, moreover, are different for different types of dislocations and slip systems. Then, the anisotropy analysis can be in principle used to characterize the particular types of occurring dislocations and activated slip system [35]. Therefore, we tested this possibility also in the NiCo2W phase for the sintered and rotary swaged samples.…”