X-ray Powder Diffraction System

X-ray diffraction is a common technique for the study of crystal structures and atomic spacing.

X-Ray Power Diffraction System

Martin Pueschel © Australian Museum


The PANanlytical X’Pert Pro XRD is a theta to theta goniometer system. The sample stays at the levelled position during the measurement.

X-ray diffraction is based on constructive interference of monochromatic X-rays and a crystalline sample. These X-rays are generated by a cathode ray tube, filtered to produce monochromatic radiation, collimated to concentrate, and directed towards the sample. The interaction of the incident rays with the sample produces constructive interference (and a diffracted ray) when conditions satisfy Bragg’s Law (nλ= 2d sinθ). This law relates the wavelength of electromagnetic radiation to the diffraction angle and the lattice spacing in a crystalline sample. These diffracted X-rays are then detected, processed and counted. By scanning the sample through a range of 2θangles, all possible diffraction directions of the lattice should be attained due to the random orientation of the powdered material. Conversion of the diffraction peaks to d-spacings allows identification of the material because each mineral has a set of unique d-spacings. Typically, this is achieved by comparison of d-spacings with standard reference patterns.

All diffraction methods are based on generation of X-rays in an X-ray tube. These X-rays are directed at the sample, and the diffracted rays are collected. A key component of all diffraction is the angle between the incident and diffracted rays.

What is X-ray powder diffraction good for?

X-ray powder diffraction is most widely used for the identification of unknown crystalline materials.

Determination of unknown solids is critical to studies in: geology, environmental science, material science, engineering and biology.

Other applications include:

  • Characterization of crystalline materials
  • Identification of fine-grained minerals such as clays and mixed layer clays that are difficult to determine optically.

     

 

 


Mr Martin Pueschel , Scientific Illustrator
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