X-ray Diffraction (XRD)
BY
SIWAPHIWE PETENI
Electromagnetic spectrum
Wilhelm Conrad Rontgen discovered X-ray in 1895
Nobel prize in physics in 1901
X-ray are high frequency electromagnetic radiation with energy
intermediate between the far UV and gamma region
English physicists Sir William.Hanry. Bragg and his son Sir William.Lawrence. Bragg
In 1913 developed a relationship to explain why the cleavage faces of crystals appear to reflect X-ray beams at certain angles of incidence (theta, q)
X-ray diffraction
XRD is a non-destructive technique
Is rapidly used for phase identification of a crystalline material and can provide information on unit cell dimensions
Single crystal
Polycrystalline Amorphous
Typical XRD machine
X-ray cube Detector Sample holder
Principle X-ray tube
Detector
Collimators
Matched filters
Crystal
Constructive interference only occurs for certain θ’s correlating to a (hkl) plane, specifically when the path difference is equal to n wavelengths.
Incident Diffracted beam
Application
To identify crystalline phases
Lattice parameters strain, grain size
Measure thickness of thin films
To determine atomic arrangement
Strengths
Easy to handle
Can be used to determine unknown mineral
Minimal sample preparation is required
XRD units are widely available
Data interpretation is relatively straight forward
Limitations
Not sensitive
Requires tenths of a gram of material which must be ground into a powder
For mixed materials, detection limit is ~ 2% of sample
Peak overlay may occur and worsens for high angle 'reflections
XRD
40 80-60
0
60
120
Intensi
ty/a.u
2theta/degree
2 theta/degrees
Inte
nsity
,au
(111)
(200) (220)
Acknowledgements Prof Nyokong
S22 lab mates
Tha