Application of a powder diffractometer equipped with a strip detector and Johansson monochromator to phase analysis and structure refinement

During the past two decades, 1D and 2D semiconductor photon-counting detectors found applications, e.g., in detection of elementary particles and in medicine. More recent is their use for the X-ray diffraction and spectroscopy, where they become highly competitive with other detector types. Practical applications of such 1D detectors, built from up to about a hundred (at laboratory diffractometers) to several hundred (at a synchrotron beamline) of strips of size of the order 0.1 x 10 turn, to diffraction purposes started at the turn of the century. In the present study, selected properties of a laboratory X-ray powder diffractometer equipped with a linear photon-counting detector and a primary-beam Johansson monochromator are described. Aberrations characteristic to Bragg-Brentano instruments equipped with linear detectors are experimentally shown to be weak for 2.1 degrees angular range covered by the detector used in this study. The counting statistics provided by this setting is shown to largely outperform that obtained with the settings equipped with point detectors. Consequently, diffraction peaks are detectable down to the level of 0.1 % intensity, permitting for identification of minor impurity phases. Using illustrative examples, it is demonstrated that, with the described instrument, phase analysis of bulk polycrystals and thin polycrystalline layers is facilitated, and that structure refinement of collected data can be successfully performed. (c) 2005 Elsevier B.V. All rights reserved.