The effect of sample displacement on x-ray diffraction results in Bragg-Brentano geometry

Abstract

The aim of the study was to investigate the effect of vertical displacement of the sample on the results of X-ray diffraction (XRD) in Bragg-Brentano geometry. Measurements were performed on an S275JR steel sample using a Phaser D2 diffractometer (Cu Kα, λ = 1.541874 [Å]) with a step size of 2θ = 0.01°. The shifts in the positions of the 2θ peaks and half-widths (FWHM) were analyzed. A comparison between the theoretical model and experimental peak shifts has been calculated. The lattice constant was determined using the Nelson-Riley method, the crystallite size using the Scherrer method, and the parameters using the Williamson-Hall method. A vertical displacement of 1 mm produced an approximately 0.8° shift of the (110) peak. Based on the diffraction data, the lattice parameter was determined using the Nelson-Riley extrapolation method (2.8643-2.8678 [Å]), the crystallite size was evaluated using the Scherrer method (110-260 [Å], with the largest value for the (110) peak), and lattice distortions were assessed using the Williamson–Hall approach (approx. 0.26-0.30[%]). The results highlight the significance of precise sample positioning, as even a small displacement can lead to noticeable errors in peak locations and consequently in the derived structural parameters.