X-ray diffraction extinction in strongly textured Ag, studied through the comparison of different order of reflections

Abstract

Integrated intensity ratios of second- to first-order X-ray reflections were measured from a strongly textured pure silver sample, oriented at the maximum pole density, using several wavelengths. This was done to determine whether extinction exists in strongly textured polycrystals, as suggested by pole figure measurements, where pole density maxima of the second-order reflection often exceeds those of the first-order reflection. The integrated intensities of the reflections were normalized using the corresponding integrated intensities from a powder sample. The dominant texture of the silver sample was [110]< 011 >, and the ratios were measured for the 111 and 222 reflection pairs. All resulting ratios were larger than 1, indicating the presence of extinction, which affects first-order reflections more significantly than second-order reflections. Considering the larger number of possible reflections of a polycrystal compared to the few number of reflections of a single crystal, double diffraction between different grains is proposed here as the cause of the observed effect, similar to the well-known secondary extinction in single crystals. To investigate whether a texture gradient could influence the results, EBSD observations were conducted on the sample. A heterogeneous texture was revealed at the edges, but these heterogeneities were not found to affect the results.