Explain the construction and working of X-Ray diffractometer.

10.A] Explain the construction and working of X-Ray diffractometer.

Answer:-

Principle of X-Ray Diffractometer:
X-ray diffractometer is based on the principle of Braggs’ Law The constructive interference of monochromatic Xrays reflected by a crystalline sample is studied.

• Construction of XRD
  • The main arrangements consist of X-Ray source, Specimen and Detector.
  • The X-ray radiation generated by an X-ray tube is collimated by passing through soller slits.
  • Soller Slits are the arrangement of closely spaced thin metal plates in parallel to prevent beam divergence.
  • A divergent X-ray beam from the soller slits strikes the specimen.
  • X-rays are diffracted by the specimen on the mount(turntable) and form a convergent beam at the receiving soller slits before they enter a detector.
  • The diffracted X-ray beam is passed through the monochromator before being received by the detector.
  • The monochromatic filter is used suppress wavelengths other than K_α radiation. • The detector and the turn-table are so coupled, if the crystal is rotated through an angle θ then the detector turns through an angle 2θ.
  • The reflected X-rays are collimated and manochromatic X-rays from the monochromator are collected by the detector.
  • The intensity of the reflected X-ray beam as a function of 2θ is recorded in a computer.
  • A plot of Intensity as a function of 2θ. thin-film XRD requires a parallel incident beam, not a divergent beam as in regular diffractometry.
  • The small glancing angle of the incident beam ensures that sufficient diffraction signals come from a thin film or a coating layer instead of the substrate.