X-Ray Diffractometre (XRD)

Method:
X-rays, being electromagnetic waves, are susceptible to diffraction. Having wavelengths similar to the inter atomic distances in crystals, they interact with a crystal lattice in the same way that light interacts with a conventional diffraction grating. In other words, they are dispersed in different directions according to wavelength. An important difference is that X-rays penetrate below the surface of the crystal and rays reflected from successive atomic layers may or may not be in phase. The condition for a maximum of reflected intensity is that the contribution from successive planes should be in phase. If the interplanar spacing is d, the condition is expressed by the well known Braggs law:

nl=dsinq

XRD Laboratory

where l is the wavelength of the incoming X-rays, q is the diffraction angle which is equal to the angle of incidence of the incoming X-rays and n is an integer. If the X-ray beam is monochromatic and l is known, the beam will undergo diffraction by the crystals to form a diffraction pattern of sharp reflections. Measurements of the various q angles can be used to determine the interplanar spacing d characteristic of the diffraction crystal. X-ray powder diffraction provides a powerful technique for mineral identification. The sample has to be crushed to a fine powder, but very little is necessary for an identification. The technique can be used for identification of all crystalline materials.