XRD

Fundamentals of X-ray Diffraction X-Rays are electromagnetic radiation of exactly the same nature as light, but of very much shorter wavelength. The unit of measurement in the X-ray region is the angstrom (Å), equal to 10-10 m and X-rays used in diffraction have wavelengths lying in the range of 0.5-2.5 Å where as visible light is of the order of 6000 Å. X-rays are produced when any electrically charged particle of sufficient kinetic energy decelerates. Electrons are usually used for this purpose, the radiation being produced in an X-ray tube which contains a source of electrons and two metal electrodes. The high voltage maintained across these electrodes draws the electrons to the anode, or target, which they strike with high velocity. X-rays are produced at the point of impact and radiate in all directions. Most of the kinetic energy of the electrons striking the target is converted into heat, less than 1% being transformed into X-rays.

When the rays coming from the target are analyzed, they are found to contain a mixture of different wavelengths, and the variation of intensity with wavelength is found to depend on the tube voltage. The intensity is zero up to a certain wavelength, called the short wavelength limit (λSWL), increases rapidly to a maximum then decreases, with no sharp limit on the long wavelength side.




Figure 1: A graphical representation of X-ray Radiation
Diffracting from crystal planes and what Bragg's law
represents


Figure 2: D8 Advance, Brucker-AXS


Figure 3: Example of 2θ-scans with peak index and different phases