The mineral concentrations are reported as percentages, with the total being normalised to 100%. An estimation of the total amorphous content can also be given. Semi-quantitativein which the phase identification includes a concentration which is calculated using the normalized reference intensity ratio method where the intensity of the 100% (highest) peak divided by the published correction factor for each mineral phase is summed and the relative percentages of each phase calculated based on the relative contribution to the sum.Qualitative XRD where the phase identification is conducted and the minerals are classified as major, minor and trace.The techniques we frequently utilise are: We have a myriad of different holding mounts to assist in the analysis of the samples including our standard holders that utilise approximately one cubic centimetre of powdered sample, holders that take milligram quantities of sample, holders that can present filter cloth, flat ceramic or metallic plates and holders that can accommodate some sample irregularity. Utilising a number of diffraction databases including the latest 2019 complete International Centre for Diffraction Database (ICDD) to assist in the accurate analysis of unknown samples. Due to the poor crystallinity and irregular orderingof some clay groups, identification may require additional sample preparation methods including glycolation, heat (dehydration) and other techniques.Īt Microanalysis we have several automated powder X-ray Diffractometers. One of the most challenging areas for phase identification is clay speciation. Quantification XRD techniques vary from qualitative (what is present) to semi quantitative (what and relative abundance of what is present) through to fully Quantitative Rietveld analysis. The use of elemental assay information (say from XRF), sample history and geology/location information and complimentary techniques all assist by strengthening confidence in making phase identification more accurate. Other information than can be gleaned from a diffraction pattern includes the degree of weathering or alteration, crystallite size, elemental substitution, the degree of disorder, and the amorphous content. Confidence in matching the phases can vary depending on how closely the standardised database pattern match the minerals present in the sample, the number and type of other phases present in the sample, crystallinity, concentration of the individual phases and the quality of the diffraction pattern as well as the grinding/micronizing process itself. Note that elemental composition is not determined by XRD, but can be inferred from the phases identified. By using this interpretation technique, it is possible to identify well over ten different minerals or crystalline phases within an unknown sample, as long as they are present in concentrations that exceed ~1%. The interpretation of the diffraction pattern is a comparative method where the data is matched to an exhaustive list of reference patterns. ![]() The resulting peaks or humps are similar to a fingerprint, as they can be matched to specific mineral or crystalline phases. The scan results in a diffraction pattern which contains numerous peaks or humps. As the X-rays come into contact with the particulate material, they are diffracted by the crystal structure of the phase or phases that are being analysed. The instrument bombards the powdered sample with X-rays at varying angles. X-ray Diffraction (XRD) is a technique that is utilized to identify crystalline phases present in a given sample.įor powder diffraction, a micronized sample is pressed into a specialised holder and placed into the X-ray Diffractometer.
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