3. X-Rays are electromagnetic radiation with
wavelengths in the range 0.1 - 100 Å (0.01-10nm)
X Rays used in diffraction experiments have
typical wavelengths of 0.5 - 1.8 Å
X-rays were discovered by Wilhelm Roentgen
who called them X-rays and it also called as
X-ray diffraction was discovered by Max von
Laue in 1912.
5. In an atom, the electrons
are arranged in layers or
6. When the atom is bombarded with an electron,
eject one of the electron from the inner shell.
The electrons migrate from the outer shell to the
inner shell to fill the gap with higher energy.
A quantum of radiation (X-rays)is emitted
corresponding to this transition , time scale is
Emitted radiation is called X-rays.
10. X-rays are obtained in three ways.
By bombardment of metal target with a
beam of high energy electrons.
By exposure of a substance to a primary
beam of X-rays in order to generate a
secondary beam of X-ray fluorescence.
By use of radioactive source decay process
results in X-ray emission.
13. There are four methods available.
X-ray absorption methods
X-ray Emission methods
X-ray fluorescence methods
X-ray diffraction methods.
14. X-Ray absorption methods:-
A beam of X-rays is allowed to pass through
the sample and fraction of X-ray photons absorbed
is considered to be a measure of the concentration
of the absorbing substance.
X-Ray emission methods:-
X-ray are obtained by employment of
radioactive source whose decay process results in
15. X-ray fluorescence:-
In these methods, X-rays are generated within
the sample and by measuring the wavelength and
intensity of the generated X-rays, one can perform
qualitative and quantitative analysis.
These methods are based on the scattering of
x-ray by crystals. This method is used to identify
the crystal structures of various solid compounds.
16. A beam of X-ray is passed to the sample
X-ray photons absorbed by the substance.
Measuring the concentration of absorbing substance.
Elemental analysis such as barium and iodine in
17. Beam of X-ray fall on sample
Emits secondary X-ray
Intensity of X-ray provides
how much is present
19. X-ray tube:-
High velocity of electrons bombarded on metal
target, X-rays are produced.
Close metal plates separated by small gap.
Use is to produce narrow beam.
Absorbs the undesirable radiations and allows
required wavelength to pass.
Filter -E.g. Zirconium
Crystal -E.g. Sodium chloride, Lithium fluoride
21. When X-rays interact with a solid material, the
scattered beams can add together in a few
directions and yield diffraction.
24. X-ray diffraction is based on constructive
interference of monochromatic x-rays and a
These x-rays are generated by a cathode ray tube,
filtered to produce monochromatic radiation
,collimated to concentrate and directed towards
The interaction of incident rays with the sample
produces constructive interference when
conditions satisfy Bragg’s law.
25. The relationship describing the angle at which a
beam of X-rays of a particular wavelength diffracts
from a crystalline surface was discovered by
William Bragg and Lawrence Bragg and is known
as Bragg’s law.
31. Using the Laue's photograph, Bragg analysed the
structures of crystals of sodium chloride, Kcl.
Bragg devised a spectrometer to measure the
intensity of X-ray beam.
The spectra obtained in this way can be employed
for crystallographic analyses.
This is based on the Bragg’s equation:
nλ = 2dsinϴ
35. A beam of X-ray beam is fall on to the powedered
specimen through slits.
The sharp lines to be obtained on the photographic
film which is surrounding the powder crystal in the
form of circular arc.
Powder diffraction patterns are typically plotted as
the intensity of the diffracted X-rays vs. the angle 2θ.
Peaks will appear in the diffraction pattern at 2θ
values when constructive interference is at a
maximum, when Bragg’s Law is satisfied.
n λ = 2 d sin θ
38. Identification of single phase materials-Minerals, chemical
Identification of multiple phases in microcrystalline
Determination of crystallite size and shape.
Crystallographic structural analysis and unit cell calculation for
Particle size determination-Spot counting methods,
-Broadening of diffraction lines