Principle and production of X rays, Bragg's law of diffraction, X-ray diffraction methods.

1. Pallavi Kumbhar
MSc Part-I (Sem-2)

2. CONTENTS:
01 INTRODUCTION
02 PRODUCTION OF X-RAYS
03 PRINCIPLE
04 BRAGG’S LAW OF DIFFRACTION
05 X-RAY DIFFRACTION METHODS
1) Laue’s Method
• 2) Rotating Crystal Method
• 3) Powder method
06 APPLICATIONS OF XRD
07 REFERENCES

3.  X-ray spectroscopy is a general term for
several spectroscopic techniques for characterization
of materials by using x-ray excitation.
 Types of X-ray spectroscopy:
1. X-ray Fluorescence
2. X-ray Diffraction
3. X-ray Absorption
 X-ray diffraction is a technique which is used
to determine a sample's composition and crystalline
structure.
 For larger crystals such as macromolecules and
inorganic compounds, it can be used to determine the
structure of atoms within the sample.
 If the crystal size is too small, it can determine sample
composition, crystallinity, and phase purity.

4. PRODUCTION OF X-RAYS
1. The energy released through heating
enables electrons to be released from
the filament through thermionic
emission.
2. The electrons are attracted towards
the positively charged anode and hit
the tungsten target with a maximum
energy.
3. As the electrons bombard the target,
they interact via characteristic
interactions and converts energy into
heat and x-ray photons.
4. The x-ray photons are released in a
beam with a range of energies which is
called as x-ray spectrum.

6. According to Bragg Equation:
nλ = 2d sinθ
Therefore, according to the derivation of Bragg’s Law:
1) λ is the wavelength of the incident X-ray beam.
2) d is the interplanar distance between the atomic layers
3) Θ is the angle of incidence
4) n is an integer.
In XRD (X-ray diffraction) the inter-planar spacing or d-spacing
of a crystal is used for characterization and identification
purposes.

7. X-RAY DIFFRACTION
METHODS
LAUE ROTATING CRSYSTAL POWDER

8.  A beam of polychromatic X-rays of wavelengths
ranging from 0.2Å to 2Å is allowed to fall on a small
crystal of dimension 1x1x1(mm), placed on a
goniometer.
 The X-ray falls on different Bragg’s planes having a
spacing d and making different angles ‘θ’ with the
incident direction of X-rays.
 For some value of d, λ and θ, which satisfy the Bragg’s
condition, constructive interference takes place and
increase in intensity takes place at certain directions
producing a diffraction pattern.
NOTE: The Laue method cannot be used for the determination of crystal structure. It is because that out of the
continuous range of wavelengths, a number of wavelengths may be reflected in different order from a single plane
producing and overlapping of certain reflections at a single spot.

9.  In this method, a single crystal of dimension 1 mm, is
mounted on a rotating spindle such that the axis of
rotation of the spindle coincides with either of the axis of
the crystal.
 A beam of monochromatic X-rays is incident on the crystal
perpendicular to the axis of rotation of the spindle.
 The spindle is covered by a Hollow cylindrical holder
having its axis collinear with the axis of spindle such that
the crystal lies at the centre of this cylindrical holder.
 For obtaining the diffraction pattern a photographic plate
is attached inside the cylindrical holder along with its
surface.

10.  The monochromatic rays are collimated into a fine beam
by passing them through two lead slits and are made to
fall on the powder specimen.
 A small sample of fine powder is taken in a capillary tube
made up of non-diffracting material and suspended along
the axis of the cylindrical camera having a photo film
attached around its inner surface.
 This camera is called Debye-Scherrer camera and
surrounds the crystal powder completely in all directions
up to an angle of 180 degrees with the direction of
incident X-rays.
 When the film is developed and laid flat on a table, the
shape of the Rings is obtained.

11. APPLICATIONS OF X-RAY DIFFRACTION
1. PHARMACEUTICAL
INDUSTRY
XRD is the key technique for
solid-state drug analysis,
benefiting all stages of drug
development, testing and
production.
2. FORENSIC SCIENCE
Identification and comparison
of trace quantities of material
can help in the conviction or
exoneration of a person
suspected of involvement in a
crime.
3. GEOLOGICAL APPLICATIONS
Each mineral type is defined by a
characteristic crystal structure,
which will give a unique x-ray
diffraction pattern, allowing rapid
identification of minerals present
within a rock or soil sample.
4. MICROELECTRONICS INDUSTRY
XRD topography can easily detect and
image the presence of defects within a
crystal, making it a powerful non-
destructive evaluation tool for
characterizing industrially important
single crystal specimens.
5. GLASS INDUSTRY
XRD is used in identification
of crystalline particles which cause
tiny faults in bulk glass, and
measurements of crystalline
coatings for texture, crystallite size
and crystallinity.

12. • Principles of Instrumental Analysis - Skoog, Holler and Nieman
• Physical Chemistry Of Macromolecules (2nd edition)
• https://physicswave.com/x-ray-diffraction-analysis-principle-instrument-and-applications
• https://microbenotes.com/x-ray-spectroscopy-principle-instrumentation-and-applications
• https://www.radiologycafe.com/radiology-trainees/frcr-physics-notes/production-of-x-
rays
• Applications of XRD | MyScope