X-ray diffraction is used to identify clay minerals by analyzing their atomic structure. When X-rays interact with the planes of atoms in a crystalline structure, they are either scattered or diffracted based on Bragg's law. This produces a unique diffraction pattern that can be used to identify different minerals. Modern X-ray diffractometers work by generating X-rays, directing them at a sample, detecting the diffracted X-rays, and analyzing the diffraction pattern to identify the minerals present in the sample.

1. X-RAY DIFFRACTION OF
CLAY MINERALS
Presented By:-
Shaheen Praveen
M.Sc. (Ag.)
Deptt. of SS&AC
College of Agriculture, IGKV
Raipur

2. INTRODUCTION

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
X-ray diffraction analysis is one of the principle
method involved in identification of clay minerals
by using specific properties of clay minerals.
 X-ray diffraction is a technique that provides
detailed information about the atomic structure of
crystalline substances. It is a powerful tool in the
identification of minerals in rocks and soils

4. PRINCIPLE
 When a focused X-ray beam interacts with planes of atoms, part of
the beam is transmitted, part is absorbed by the sample, part is
refracted and scattered, and part is diffracted.
 Diffraction of an X-ray beam by a crystalline solid is analogous to
diffraction of light by droplets of water, producing the familiar
rainbow.
 X-rays are diffracted by each mineral differently, depending on what
atoms make up the crystal lattice and how these atoms are arranged.
 When an X-ray beam hits a sample and is diffracted, we can
measure the distances between the planes of the atoms that
constitute the sample by applying Bragg's Law, named after

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Willium Lawrence Bragg, who first proposed it in 1921.
Bragg's Law is: nλ =2d sinθ,
where the integer n is the order of the diffracted beam, is the wavelength
of the incident X-ray beam, d is the distance between adjacent planes of
atoms (the d-spacings), and is the angle of incidence of the X-ray beam.
 The geometry of an XRD unit is designed to accommodate this
measurement.
 The characteristic set of d-spacings generated in a typical X-ray scan
provides a unique "fingerprint" of the mineral or minerals present in the
sample.
 When properly interpreted, by comparison with standard reference
patterns and measurements, this "fingerprint" allows for identification of
the material.

6. PROCEDURE
1. Generation of X-rays
2. X- ray diffraction
3. Detection
4. X-ray diffraction analysis

7. Generation of X-rays
 In X-ray diffractometry, X-rays are generated within a sealed tube
that is under vacuum.
 A current is applied that heats a filament within the tube; the
higher the current the greater the number of electrons emitted
from the filament.
 This generation of electrons is analogous to the production of
electrons in a television picture tube.
 A high voltage, typically 15-60 kilovolts, is applied within the tube.
This high voltage accelerates the electrons, which then hit a target,
commonly made of copper.
 When these electrons hit the target, X-rays are produced. The
wavelength of these X-rays is characteristic of that target.

8. Working Principle

9. Working Principle

10. X-RAY DIFFRACTION
 X-ray diffraction occurs when X-rays are scattered by atoms arranged in
an orderly array in crystals.
 The atoms serve as scattering centers (Moore and Reynolds, 1997), re-
emitting X-rays at the same wavelength as the incident radiation in all
directions (coherent scattering).
 The orderly arrangement of atoms results in the scattered X-rays within
the crystal being (i) in phase in specific directions dictated by symmetry
and atomic spacings and (ii) out of phase in all other directions .
 The X-rays that are in phase constructively interfere and emerge as
intense beams (diffracted beams) from the crystal, while those that are
out of phase destructively interfere and hence have minimal emergence.
This systematic combination of constructive and destructive interference
arising from the periodicity of atoms in crystals is X-ray diffraction.

11. X-ray Diffraction

12. DETECTION
A detector detects the X-ray signal; the signal
is then processed either by a microprocessor
or electronically, converting the signal to a
count rate. Changing the angle between the X-
ray source, the sample, and the detector at a
controlled rate between preset limits is an X-
ray scan.

13. X-RAY DIFFRACTION
ANALYSIS
 Obtaining useful information from XRD requires the ability to control
and/or measure angular relations between incident and diffracted
radiation.
 Two types of instruments have been used to perform X-ray diffraction
analysis: the XRD powder camera and the X-ray diffractometer.
 The powder camera approach entails recording diffraction maxima
“cones” on cylindrically mounted photographic film surrounding the
specimen.
 The diffractometer records the intensity of the diffracted beam
electronically at precise angles as the specimen is scanned over an angular
range.
 Modern diffractometers have a number of advantages over the powder
camera and are the more commonly used instruments in soil mineralogy.
 Therefore, the diffractometer approach will be emphasized in this chapter,
but the d-spacing and intensity data obtained from either type of
instrument are interpreted the same way.

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