XRF and XRD are two common x-ray techniques. Each has advantages and disadvantages to its specific method of scanning and measuring. Though these techniques have numerous applications, XRF and XRD are mostly used in scientific industries for the measurement of compounds. The type of compound and its molecular structure designates which technique will be more effective.
X-ray powder diffraction—or XRD—is used to measure crystalline compounds and provides a quantitative and qualitative analysis of compounds that cannot be measured by other means. By shooting an X-Ray at a compound, XRD can measure the diffraction of the beam from different sections of the compound. This measurement can then be used to understand the composition of the compound on an atomic level, since all compounds diffract the beam differently. XRD measurements show structural make-up, content and size of crystalline structures.
X-Ray Fluorescence—or XRF—is a technique that is used to measure the percentage of metals within inorganic matrices such as cement and metal alloys. XRF is an especially useful research and development tool in construction industries. This technique is extremely useful for determining the make-up of these materials, allowing for higher-quality cements and alloys to be developed.
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XRF can be performed fairly quickly. An XRF measurement, which measures the metal in the given sample, can be set up in under an hour. The result analysis also maintains the advantage of being quick, typically only taking 10 to 30 minutes to develop, which contributes to the usefulness of XRF in research and development.
Since XRF measurements rely on quantity, there are limits on the measurements. The normal quantitative limit is 10 to 20 ppm (parts per million), usually the minimum particles required for an accurate reading.
XRF also can’t be used to determine Beryllium content, which is a distinct disadvantage when measuring alloys or other materials that might contain Beryllium.
XRD also has size limitations. It is much more accurate for measuring large crystalline structures rather than small ones. Small structures that are present only in trace amounts will often go undetected by XRD readings, which can result in skewed results.