 |
 |
Technique:
XRD is used for the identification of crystalline materials, primarily minerals using crystallography. Patterns, produced by reflecting X-rays off the crystal planes at the atomic level, are detected and recorded. Analysis is accomplished by determining the inter-atomic spacing and comparing the results to a reference library.
Application:
It is the definitive test in the detection and quantification of silica and its polymorphs.
The Science Behind:
Sample preparation is a critical area in XRD. The specimen needs to be a randomly oriented powder with a particle size of less than 10 micrometers, placed on the testing tray. X-rays, reflected off the atomic planes of the specimen, creating interference wave patterns. These waves, like all waves, interfere with each other, producing what are known as diffraction patterns. The diffraction patterns are recorded and analyzed. When compared to a reference database, the unique crystalline structure can be identified.
The fundamental equation for the diffraction of waves is Bragg's law 'nλ=2dsinθ', in which λ is wavelength, d is separation distance, n is diffraction order and θ is the angle of incidence.
Other Resources:
Wikipedia Definition of X-ray scattering techniques
Wikipedia Definition of Crystallography
Crystallography - The study of the formation and properties of crystals.
Minerals - Minerals are natural compounds formed by geological process from pure elements and simple salts.
Specimen - A small portion of the sample to be tested.
X-rays - A section of the electromagnetic spectrum ranging from approximately 10 pm to 10 nm in wavelength.
Minerals - Minerals are natural compounds formed by geological process from pure elements and simple salts.
Specimen - A small portion of the sample to be tested.
X-rays - A section of the electromagnetic spectrum ranging from approximately 10 pm to 10 nm in wavelength.