X-Ray Diffraction
X-Ray Diffraction
Analytical Lab
Environmental Testing Lab
X-Ray Diffraction
Analytical Lab
Analytical Lab
Environmental Testing Lab
Materials Testing Labs
X-Ray Diffraction
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.
X-Ray Diffraction
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:
  • Angles are used to calculate the interplanar atomic spacings (d-
    spacings). Because every crystalline material will give a characteristic
    diffraction pattern and can act as a unique ‘fingerprint’, the position (d)
    and intensity (I) information are used to identify the type of material by
    comparing them with patterns for over 80,000 data entries in the
    International Powder Diffraction File (PDF) database, complied by the
    Joint Committee for Powder Diffraction Standards (JCPDS). By this
    method, identification of any crystalline compounds, even in a complex
    sample, can be made.
  • The position (d) of diffracted peaks also provides information about
    how the atoms are arranged within the crystalline compound (unit cell
    size or lattice parameter). The intensity information is used to assess
    the type and nature of atoms. Determination of lattice parameter helps
    understand extent of solid solution (complete or partial substitution of
    one element for another, as in some alloys) in a sample.
  • Width of the diffracted peaks is used to determine crystallite size and
    micro-strain in the sample.
  • The ‘d’ and ‘I’ from a phase can also be used to quantitatively estimate
    the amount of that phase in a multi-component mixture.
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X-Ray Diffraction
Quantitative analysis
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.


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X-Ray Diffraction
Technology of Materials
Analysis of Materials by XRay Diffraction (XRD)
What is X-Ray Diffraction?