introduction to xray, bragg's law, miller indices,,,powder diffraction, instrumentation, application

1. X-Ray Diffraction
Bindu Kshtriya

2. DISCOVERY OF X-RAY
Wilhelm Conrad Roentgen discovered x-
radiation in 1895
In 1912, Friedrich, Knipping, and von Laue
demonstrated diffraction of x-radiation
passing through a crystal
The wavelength of x-radiation ranges from
10-6 to 10-1 nm
2

3. W Cathode CuAnode
(-) (+)
X -rays
electrons
X-RAY GENERATION

4. ENERGY LEVELS

5. XRD
The atomic planes of a crystal
cause an incident beam of X-
rays to interfere with one
another as they leave the
crystal. The phenomenon is
called X-ray diffraction.

6. SCHEMATIC DIAGRAM OF X-RAY
DIFFRACTION

9. Constructive and Destructive
Interference of Waves
Constructive Interference
In Phase
Destructive Interference
Out of Phase

10. smallest building block
c
a
b a
g
Unit cell
(Å)
CsCl
b
d1
Lattice d2
A crystal consists of a periodic arrangement of the unit cell into a
lattice. The unit cell can contain a single atom or atoms in a fixed
arrangement.
Crystals consist of planes of atoms that are spaced a distance d apart,
but can be resolved into many atomic planes, each with a different d
spacing.
A , b and c (length) and a α, β and γ angles between a , b and c are lattice
constants or parameters which can be determined by XRD.

11. SEVEN CRYSTAL SYSTEM

12. MILLER INDICES
Miller indices-the reciprocals of the
fractional intercepts which the
plane
makes with crystallographic axes
Axial length 4Å 8Å
3Å
Intercept lengths 1Å 4Å
3Å
Fractional intercepts ¼ ½ 1
Miller indices 4 2 1
h k l

13. Several Atomic Planes and Their d-spacings
in
a Simple Cubic
a b c
1 0 0
1 0 0
a b c
1 1 1
1 1 1
a b c
1 1 0
1 1 0
a b c
0 1 ½
0 1 2
Cubic
a=b=c=a
0

14. WHY XRD
• Measure the average spacings between
layers or rows of atoms
• Determine the orientation of a single
crystal or grain
• Find the crystal structure of an unknown
material
• Measure the size, shape and internal
stress of small crystalline regions

15. X-RAY POWDER
DIFFRACTION
X-ray powder diffraction (XRD) is a
rapid analytical technique primarily used
for phase identification of a crystalline
material and can provide information on
unit cell dimensions. The analyzed
material is finely ground, homogenized,
and average bulk composition is
determined

17. X-RAY POWDER
DIFFRACTOMETER1.) The X-ray
tube
2.) The flat specimen
3.) The goniometer circle
5.) A slit
6.) A filter
7.) The detector
4.) Monochromator

18. Basic Features of Typical XRD
Experiment

19. Steps involved :-1.) Sample preparation
2.) Generate Analytical X-rays
3.)Direct the X-rays at a Powdered Specimen
4.) Measure X-Rays “Diffracted” by the
specimen and obtain a diffraction pattern
5.) Determine the Crystalline Phases
Present in the specimen

20. DETECTORS
PHOTOGRAPHIC
METHODS
GEIGER MULLER
TUBE METHOD
PROPORTIONAL
COUNTER
SCINTILLATION
DETECTOR
COUNTER
METHODS

21. DIFFRACTION SPECTRA

22. INTERPRETATION OF
DATA
•International Centre Diffraction Data (ICDD) or
formerly known as (JCPDS) Joint Committee on
Powder Diffraction Standards is the organization that
maintains the data base of inorganic and organic
spectra.
•The data base is available from the Diffraction
equipment manufacturers or from ICDD direct.
•Currently the data base is supplied either on magnetic
or optical media. Two data base versions are available
the
PDF I and the PDF II.

23. •The PDF I data base contains information on d-spacing,
chemical formula, relative intensity, RIR quality information and
routing digit.
•The information is stored in an ASCII format in a file called
PDF1.dat. For search/match purposes most diffraction
manufactures are reformatting the file in a more efficient binary
format.
•The PDF II data base contains full information on a particular
phase including cell parameters. Scintag’s newest search/match
and look-up software package is using the PDF II format.
•Optimized data base formats, index files and
high performance PC-computers make PDF II search times
extremely efficient.

24. Significance of Peaks in XRD
1. Peak position
2. Peak width
3. Peak intensity
4. Peak area
5. Peak shape

25. omy” of the XRD pattern
rmation content of an idealized diffraction pattern.
28

26. Uses of X-Ray Powder
Diffraction
• Identification of single-phase materials –
minerals, chemical compounds, ceramics or
other engineered materials.
• Identification of multiple phases in
microcrystalline mixtures (i.e., rocks)
• Determination of the crystal structure of
identified materials
• Identification and structural analysis of clay
minerals
• Recognition of amorphous materials in
partially crystalline mixtures

27. Applications of XRD
• XRD is a non destructive technique
• To identify crystalline phases and orientation
• To determine structural properties:
Lattice parameters (10-4Å), strain, grain size,
expitaxy, phase composition, preferred orientation
(Laue) order-disorder transformation, thermal
expansion
• To measure thickness of thin films and multi-layers*
• To determine atomic arrangement
• Detection limits: ~3% in a two phase mixture; can be
~0.1% with synchrotron radiation
Spatial resolution: normally none

28. Thank you
Bindu Kshtriya