X-ray powder methods

(redirected from Powder diffraction)
Also found in: Wikipedia.

X-ray powder methods

Physical techniques used for the identification of substances, and for other types of analyses, principally for crystalline materials in the solid state. In these techniques, a monochromatic beam of x-rays is directed onto a polycrystalline (powder) specimen, producing a diffraction pattern that is recorded on film or with a diffractometer. This x-ray pattern is a fundamental and unique property resulting from the atomic arrangement of the diffracting substance. Different substances have different atomic arrangements or crystal structures, and hence no two chemically distinct substances give identical diffraction patterns. Identification may be made by comparing the pattern of the unknown substance with patterns of known substances in a manner analogous to the identification of people by their fingerprints. The analytical information is different from that obtained by chemical or spectrographic analysis. X-ray identification of chemical compounds indicates the constituent elements and shows how they are combined.

The x-ray powder method is widely used in fundamental and applied research; for instance, it is used in the analysis of raw materials and finished products, in phase-diagram investigations, in following the course of solid-state chemical reactions, and in the study of minerals, ores, rocks, metals, chemicals, and many other types of material. The use of x-ray powder diffraction methods to determine the actual atomic arrangement, which has been important in the study of chemical bonds, crystal physics, and crystal chemistry, is described in related articles. See X-ray crystallography, X-ray diffraction

There are many types of powder diffractometer available ranging from simple laboratory instruments to versatile and complex instruments using a synchrotron source. Specialized instruments allow recording of diffraction patterns under nonambient conditions, including variable temperature, pressure, and atmosphere. Completely automated equipment for x-ray analysis is available. Most laboratory instruments consist of a high-voltage generator which provides stabilized voltage for the x-ray tube, so that the x-ray source intensity varies by less than 1%. A diffractometer goniometer is mounted on a table in front of the x-ray tube window. Electronic circuits use an x-ray detector to convert the diffracted x-ray photons to measurable voltage pulses, and to record the diffraction data.

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Rietveld Refinement: Practical Powder Diffraction Pattern Analysis Using TOPAS
Therefore, in this work a complete structural analysis of the ternary compound [Ag.sub.2]Sn[Te.sub.3] is performed by using X-ray powder diffraction data.
In Figure 3 is shown the X-ray diffraction patterns for all of the hydrotalcite samples, where it is possible to observe the R-3m rhombohedral phase as a single phase in the precipitate samples, despite of the iron insertion, according the card number 89-5434 of the JCPDS data bank for powder diffraction patterns.
Structural and phase evolution was studied in situ by high-resolution neutron powder diffraction performed with the SPODI instrument at FRM II, Garching, Germany [7], equipped with a high-temperature furnace.
They showed that the X-ray powder diffraction (XRD) data consisted of iron oxide corrosion products in the form of goethite [FeO(OH)], magnetite [[Fe.sub.3][O.sub.4]] and lepidocrocite [FeO(OH)], iron sulfide corrosion products in the form of pyrite [Fe[S.sub.2]] and pyrrhotite [[Fe.sub.7][S.sub.8]], and formation materials in the form of quartz [Si[O.sub.2]].
Aeris, from PANalytical, is an X-ray powder diffraction (XRD) benchtop instrument that is easily accessible for everyone, featuring a built-in touchscreen computer and intuitive software.
The NIST lattice comparator has played a critical role in determining the variability and absolute lattice parameters of single-crystal silicon used to produce powder diffraction SRMs.
Rietveld refinement was applied on X-ray powder diffraction data of Submicronic HMMS calcium zincate sample without preferential orientation.
- X-ray powder diffraction and scattering techniques
Applications for the detectors include: X-ray powder diffraction and scattering techniques; residual stress measurements; thin film and texture analysis; PDF (Pair distribution function) analysis; X-ray scattering (SAXS), wide-angle X-ray scattering measurements (WAXS) and grazing incidence small angle scattering (GISAXS); and dispersive fluorescence spectroscopy.