|X-ray powder diffraction (XRD) is one of the most powerful technique for
qualitative and quantitative analysis of crystalline compounds. The
technique provides information that cannot be obtained any other way. The
information obtained includes types and nature of crystalline phases
present, structural make-up of phases, degree of crystallinity, amount of
amorphous content, microstrain & size and orientation of crystallites.
|Principles of Operation
|When a material (sample) is irradiated with a parallel beam of
monochromatic X-rays, the atomic lattice of the sample acts as a three
dimensional diffraction grating causing the X-ray beam to be diffracted to
specific angles. The diffraction pattern, that includes position (angles) and
intensities of the diffracted beam, provides several information about the
sample and are discussed below:
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|As mentioned earlier, XRD can be used not only for qualitative identification
but also for quantitative estimation of various crystalline phases. This is one
of the important advantage of X-ray diffraction technique. Several methods
have been proposed and successfully used to quantify crystalline phases in
mixtures. They include external standard methods, the
reference-intensity-ratio (RIR) method, chemical methods and the whole
pattern fitting Rietveld method. Of the available methods, the Rietveld
method is probably the most accurate and reliable method. The Rietveld
method is a whole-pattern fitting least squares refinement technique and
has been successfully used for quantification and characterization of
inorganic and organic compounds It has also been used for crystal structure
refinement, to determine size and strain of crystallites.
|Analysis of Materials by XRay Diffraction (XRD)