Principle of powder diffraction
Characterization of polycrystalline materials by X-Ray Diffraction

When X-rays (photons) interact with the atoms of matter, numerous phenomena occur, with the relative prevalence of these phenomena varying depending on the energy of the radiation. Here we will focus only on the case of elastic scattering, when the material emits a beam of the same wavelength as the incident radiation, transforming from a plane wave to a spherical wave.

Since the atoms in crystalline matter are arranged in a repeating pattern, the interference between the scattered waves is constructive in certain directions. This stronger signal corresponds to the phenomenon of diffraction, which occurs when Bragg’s law is satisfied (Figure1):