XRD or X-ray Powder Diffraction is an analytical technique widely used for phase identification of crystalline structures and to determine the atomic spacing. Crystalline structures act as a three dimensional diffraction grating for X-ray. In the XRD machine, a cathode ray tube generates the X-Ray. Then the X-Ray is filtered to produce monochromatic radiation and then collimated to hit the sample. The beam then produces a constructive interference when it satisfies the Bragg's Law (nλ=2dsinθ, where n is an integer, λ is the wavelength of the incident monochromatic electromagnetic radiation, and θ is the angle between the incident beam and scattering plane of the crystalline sample). For the powdered sample, the beam scans through a 2θ angle to cover all possible angles of the sample. The diffracted beam is then processed to identify the material as every crystal has a set of unique spacing.
More information about XRD is available in Wikipedia.
http://en.wikipedia.org/wiki/X-ray_crystallography
Specification and capability
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