introduction of XRD

1. NANOSAINS DAN NANOMATERIAL
X-RAY DIFFRACTIONS (XRD)
Evi Fitri (3325122134)
Universitas Negeri Jakarta
2015

2. Introduction
 X-ray diffraction is used to obtain structural information about
crystalline solids.
 Useful in biochemistry to solve the 3D structures of complex bio-
molecules.
 Bridge between physics, chemistry, and biology.
X-raydiffractionis important for
 Solid-state physics
 Biophysics
 Medical physics
 Chemistry and Biochemistry

3.  Mostuseful in the characterisation of crystalline
materials; Ceramics, metals, intermetallics,
minerals, inorganic compounds
 Rapid and nondestructive techniques
 Provide information on unit cell dimension
Structural Analysis
 X-ray diffraction provides most definitive structural
information
 Interatomic distances and bond angles
What is XRD ?

4. Electromagnetic Spectrum
 Beams of electromagnetic radiation
 *smallerwavelength than visible light,
 *higher energy
 *more penetrative
What Is X-Rays ?

5. History of X-Ray Diffraction
Wilhelm Conrad Röntgen discovered 1895 the X-rays. 1901 he was
honoured by the Noble prize for physics. In 1995 the German Post
edited a stamp, dedicated to W.C. Röntgen.

6. History of X-Ray Diffraction
 (1895) X-rays discovered by Roentgen
 (1914) First diffraction pattern of a crystal made
by Knippingand von Laue
 (1915) Theory to determine crystal structure
from diffraction pattern developed by Bragg.
 (1953) DNA structure solved by Watson and
Crick
 Now Diffraction improved by computer
technology; methods used to determine atomic
structures and in medical applications
The First X-Ray

7. X-Ray Production
• The prime componen in X-Ray tube are
filamen (catode), vacum room, anode, and
high voltage
• When high energy electrons strike an
anodein a sealed vacuum, x-raysare
generated. Anodes are often made of copper,
iron or molybdenum.
• High energy electron come from heated
filamen in X-Ray tube.
• X-rays are electromagnetic radiation.
• They have enough energy to cause
ionization.

8. Generation of X-Rays

9. Bragg’s Law
n λ = 2d sin θ
English physicists Sir W.H. Bragg and his son Sir W.L. Bragg developed a relationship in 1913 to
explain why the cleavage faces of crystals appear to reflect X-ray beams at certain angles of
incidence (theta, θ). The variable d is the distance between atomic layers in a crystal, and the
variable lambda l is the wavelength of the incident X-ray beam; n is an integer. This observation is
an example of X-ray wave interference (Roentgen strahl interferenzen), commonly known as X-
ray diffraction (XRD), and was direct evidence for the periodic atomic structure of crystals
postulated for several centuries.

10. Bragg’s Law
The Braggs were awarded the Nobel Prize in
physics in 1915 for their work in determining
crystal structures beginning with NaCl, ZnS
and diamond.

11. Bragg’s Law
Constructive interference occurs only when
 n λ = AB + BC
 AB=BC
 n λ = 2AB
 Sin θ =AB/d
 AB=d sin θ
 n λ = 2 d sin θ
 λ = 2 d sin θ

12. How Diffraction Works ?
 Wave Interacting with a Single Particle
 Incident beams scattered uniformly in all directions
 Wave Interacting with a Solid
 Scattered beams interfere constructively in some directions, producing
diffracted beams
 Random arrangements cause beams to randomly interfere and no distinctive
pattern is produced
 Crystalline Material
 Regular pattern of crystalline atoms produces regular diffraction pattern.
 Diffraction pattern gives information on crystal structure

13. Components XRD
 X-ray source
 Device for restricting wavelength range
“goniometer”
 Sample holder
 Radiation detector
 Signal processor and readout

14. How XRD works ?
 A continuous beam of X-rays is incident on the
crystal
 The diffracted radiation is very intense in certain
directions
These directions correspond to constructive
interference from waves reflected from the
layers of the crystal
 The diffraction pattern is detected by
photographic film

15. How XRD works: Bragg’s Law
 The beam reflected from the lower surface
travels farther than the one reflected from
the upper surface
 If the path difference equals some integral
multiple of the wavelength, constructive
interference occurs
 Bragg’s Law gives the conditions for
constructive interference

16. How Diffraction Works: Schematic

18. Single Crystal Diffraction
Used to determine
 crystal structure
 orientation
 degree of crystalline perfection/imperfections (twinning, mozaicity, etc.)
Sample is illuminated with monochromatic radiation
 Easier to index and solve the crystal structure because it diffraction peak is
uniquely resolved

19. Single Crystal Diffraction
A single crystal at random orientations and its corresponding diffraction pattern. Just
as the crystal is rotated by a random angle, the diffraction pattern calculated for this
crystal is rotated by the same angle

20. Single Crystal Diffraction

21. X-ray Powder Diffraction
 More appropriately called polycrystalline X-ray diffraction, because it can also be
used for sintered samples, metal foils, coatings and films, finished parts, etc.
 Used to determine
 phase composition (commonly called phase ID)-what phases are present?
 quantitative phase analysis-how much of each phase is present?
 unit cell lattice parameters, crystal structure
 average crystallite size of nanocrystallinesamples
 crystallite microstrainandtexture
 residual stress (really residual strain)

22. X-ray Powder Diffraction
A 'powder' composed from 4 single
crystals in random orientation (left) and
the corresponding diffraction pattern
(middle). The individual diffraction
patterns plotted in the same color as
the corresponding crystal start to add
up to rings of reflections. With just four
reflection its difficult though to
recognize the rings. The right image
shows a diffraction pattern of 40 single
crystal grains (black). The colored
spots are the peaks from the 4 grain
'powder' shown in the middle image.

23. Applications of X-Ray Diffraction
 Determinationof Crystalstructure
 Phaseidentification/ transition
 Grainsize / micro-strain
 Texture/stress( i.e.polymer, fiber )
 Determination of thin film composition
 Industry Identification of archeological materials

24. Advantages of XRD
 Fastidentification of materials,
 Easysample preparation,
 Computer-aidedmaterial identification,
 Large library of known crystalline structures.

25. Safetyin XRD
 Exposure types
o Short-term high-dose
o Long-term low-dose
 Invisible, odorless,colorless (most exposures undetectable)
 Lab users must understand radiation safety issues and pass an exam to use lab
 Safeguards present in lab do not substitute for knowledge and following safe
procedures

26. What are the dangerousareas?

27. Thank you