Automatic Crystal Size Determination in the Micrometer Range from Spotty X‐Ray Diffraction Rings of Powder Samples

Abstract

Crystal sizes can be calculated from peak intensities of spotty diffraction rings produced by a polycrystalline sample. Such patterns are collected using a small X‐ray beam and an area detector. Peak intensities can be automatically measured using specially designed software. Crystal sizes can be determined from peak intensities after calibration using samples of the same material whose sizes are already known. This technique is independent of the aggregation state of the material. Also, crystal sizes of different mineral phases present in a sample can be analyzed independently. The present paper analyzes the potential of this methodology as applied to crystal size characterization of crystalline powder materials. Graded SiC and α‐Al2O3 abrasive powders were selected as test material for this study. A high correlation was found between parameters determined by X‐ray diffraction and crystal size determined by means of optical microscopy and laser diffraction. The crystal sizes determined ranges from 3 to 80 μm, a much larger range than that obtained by conventional X‐ray line‐broadening analyses. Additionally, upper and lower size ranges of applicability of this technique can be extended further by using different collimator diameters. The estimated error in crystal size measurements was within 5%.

Analytical study of Roman and Arabic wall paintings in the Patio De Banderas of Reales Alcazares’ Palace using non-destructive XRD/XRF and complementary techniques

“…Because of the intensity of reflections is more sensitive than the number of reflection spots, the intensity profile of the DebyeScherrer rings has been used to qualitatively estimate the size of mineral grains. In general, the intensity of the reflections increases on average as with an increase in crystal size, and the number of spots decreases (Rodriguez-Navarro, 2006;Rodriguez-Navarro et al, 2006). Other factors that affect the intensity profile of the rings include the structure factor, the reflecting power of the compounds, and the proportion of the different crystalline phases in the samples studied.…”

“…In addition, the diffraction rings were dotted, indicating a nonhomogeneous distribution or isolated particles (Fig. 6b) (Rodriguez-Navarro, 2006;Rodriguez-Navarro et al, 2006). One of the mean XRD peaks of mica compounds is observed at 2q ¼ 9 .…”

“…The Debye-Scherrer rings contain important information on the micro-structure of the sample, including the grain size, preferential orientation, crystallinity, mosaicity, stress, etc. Spotty rings are produced by coarse-grained mineral phases, and continuous rings are produced by fine-grained mineral phases (RodriguezNavarro, 2006;Rodriguez-Navarro et al, 2006;Eveno et al, 2010). Because of the intensity of reflections is more sensitive than the number of reflection spots, the intensity profile of the DebyeScherrer rings has been used to qualitatively estimate the size of mineral grains.…”

Rapid quantification of avian eggshell microstructure and crystallographic-texture using two-dimensional X-ray diffraction

“…This information can also be automatically saved to an ASCII file. Later, crystal sizes can be determined from these values (especially from peak intensities) using a previously determined calibration curve, relating for instance average peak intensities and crystal sizes such as those determined by Rodriguez-Navarro et al (2006;in review). In this study, average peak intensities were determined for the Debye ring associated with the 104 calcite reflection using a 2D diffraction pattern collected with a transmission setup.…”

“…On the other hand, as crystal sizes increase, the intensity of reflection spots increases accordingly. Thus, from the intensity of the reflection spots of a transmission pattern, crystal size can be determined using methodology described in detail elsewhere (Rodriguez-Navarro et al, 2006;RodriguezNavarro et al, in press). Figure 3 illustrates the effect of crystal size and orientation on the diffraction patterns of eggshells having different microstructural characteristics.…”