Wide-angle X-ray scattering

In X-ray crystallography, wide-angle X-ray scattering (WAXS) or wide-angle X-ray diffraction (WAXD) is the analysis of Bragg peaks scattered to wide angles, which (by Bragg's law) are caused by sub-nanometer-sized structures.[1] It is an X-ray-diffraction[2] method and commonly used to determine the crystalline structure of polymers.

Wide-angle X-ray scattering is similar to small-angle X-ray scattering (SAXS) except the distance from sample to the detector is shorter and thus diffraction maxima at larger angles are observed. Depending on the measurement instrument used it is possible to perform both WAXS and SAXS in a single run (small- and wide-angle scattering, SWAXS).

Applications

The WAXS technique is used to determine of degree of crystallinity of polymer samples.[3] It can also be used to determine the chemical composition or phase composition of a film, the texture of a film (preferred alignment of crystallites), the crystallite size and presence of film stress. As with other diffraction methods, the sample is scanned in a wide-angle X-ray goniometer, and the scattering intensity is plotted as a function of the 2θ angle.

X-ray diffraction is a non destructive method of characterization of solid materials. When X-rays are directed at solids they scatter in predictable patterns based on the internal structure of the solid. A crystalline solid consists of regularly spaced atoms (electrons) that can be described by imaginary planes. The distance between these planes is called the d-spacing.

The intensity of the d-space pattern is directly proportional to the number of electrons (atoms) in the imaginary planes. Every crystalline solid has a unique pattern of d-spacings (known as the powder pattern), which is a fingerprint for that solid. Solids with the same chemical composition but different phases can be identified by their pattern of d-spacings.

See also

References
  1. “A new approach to wide-angle dynamical X-ray diffraction by deformed crystals” by S.G. Podorov, N.N. Faleev, K.M. Pavlov, D.M. Paganin, S.A. Stepanov, and E. Forster, J. Appl. Crystallogr., v.39 (2006)
  2. "WIDE-ANGLE X-RAY DIFFRACTION THEORY VERSUS CLASSICAL DYNAMICAL THEORY" by S.G. Podorov, A. Nazarkin, Recent Res. Devel. Optics, 7 (2009) ISBN 978-81-308-0370-8
  3. Murthy, N. S.; Minor, H. (1990-06-01). "General procedure for evaluating amorphous scattering and crystallinity from X-ray diffraction scans of semicrystalline polymers". Polymer. 31 (6): 996–1002. doi:10.1016/0032-3861(90)90243-R. ISSN 0032-3861.
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