X-ray powder diffraction method is one of the few non-destructive methods that permit the identification and the elemental analysis of materials.
As the X-Ray diffraction pattern of a crystalline substance is unique, it is possible to characterise and identify any polycrystalline substance. In order to understand the diffraction pattern, either the incident beam is monochromatic, or the X-Ray detector can resolve the energy from the Kα1, Kα2 doublet to the Kβ1 line.
Alternatively, Sollers slits / optics can be used in order to select the corresponding angular range. A resolution better than 450eV is necessary (this being the FWHM of the measured Cu Kα1, Kα2 doublet).
Diffraction patterns consist of rings and high intensity spots due to crystallised materials, which are mixed to the existing phases and averaged over continuous sample rotations. Intensity integration over those rings allow pattern indexation. Near photon counting sensitivity maybe required for standard laboratory X-ray sources whereas high brilliance sources such as microfocus / synchrotrons will require good dynamic range: One to two-megapixel detectors with spatial resolution of 60-120 microns is usually good enough for this task.