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InX-ray crystallography,wide-angle X-ray scattering (WAXS) orwide-angle X-ray diffraction (WAXD) is the analysis ofBragg peaks scattered to wide angles, which (byBragg's law) are caused by sub-nanometer-sized structures.[1] It is anX-ray-diffraction[2] method and commonly used to determine a range of information about crystalline materials. The term WAXS is commonly used inpolymer sciences to differentiate it from SAXS but many scientists doing "WAXS" would describe the measurements as Bragg/X-ray/powder diffraction orcrystallography.
Wide-angle X-ray scattering is similar tosmall-angle X-ray scattering (SAXS) but the increasing angle between the sample and detector is probing smaller length scales. This requires samples to be more ordered/crystalline for information to be extracted. In a dedicated SAXS instrument the distance from sample to the detector is longer to increase angular resolution. Most diffractometers can be used to perform both WAXS and limited SAXS in a single run (small- and wide-angle scattering, SWAXS) by adding a beamstop/knife edge.
The WAXS technique is used to determine the degree ofcrystallinity ofpolymer samples.[3] It can also be used to determine the chemical composition or phase composition of a film, the texture of afilm (preferred alignment of crystallites), the crystallite size and presence of filmstress. As with other diffraction methods, the sample is scanned in a wide-angle X-raygoniometer, 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.
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