XRD-Rotating Crystal Technique.

In this slide contains Principle, Methods, Interpretation and applications of XRD.
Presented by: Udit Narayan Singh (Department of pharmaceutics)
RIPER, anantpur.

1. 1 XRD-Rotating Crystal Technique A Seminar as a part of curricular requirement for I year M. Pharm I semester Presented by Udit Narayan Singh (Reg. No. 20L81S307 ) Dept. of Pharmaceutics Under the guidance/Mentorship of Dr. P. Ramlingam Professor Dept. of Pharmaceutical Analysis

2. 2 Introduction What is XRD ? Principle Different Methods of XRD Rotating Crystal Method XRD Plot Interpretation Pros Cons Applications Contents

3. 3 Introduction X-ray Crystallography X-ray Absorption X-ray Fluorescence X-ray Diffraction Determine the arrangement of atoms within a crystal Beam of X-rays strike a sample (Crystalline solid) and land on a detector to produce scattered beams.

4. 4 What is XRD ? Crystallography Diffraction X - Ray Experimental science of determining the arrangement of atoms in “Crystalline solids” Phenomenon of bending of waves around the corners of an obstacle High energy electromagnetic radiation. Wavelength – 10 picometer to 10 nanometer Frequency – 30 petahertz to 30 exahertz Energy – 124eV to 124KeV 0.2 to 10 nm is used in XRD, as it is comparable to interatomic spacing of crystalline solids

5. 5 XRD is based on constructive interference of X-rays and the crystalline sample Atoms in crystal refract the X-rays which are elastically scattered on to a detector This generates a 2D diffraction pattern of the crystal in a single orientation. Principle

6. 6 Crystals are made up of parallel planes of atoms Incident planes are reflected from each plane in a small fraction Constructive interference of X-rays from successive planes occurs when the path difference is an integral number of wavelength. This is Bragg’s Law. Bragg’s Law n λ = 2d Sin θ

7. 7 Different methods of XRD X – ray Diffraction Orientation Single Crystal, Polychromatic Beam, Fixed angle single θ Lattice Parameters Poly Crystal Monochromatic Beam, Variable angle many θ orientation Lattice Constant Single Crystal Monochromatic Beam, Variable angle θ varied by rotation Laue Photographic Powder Rotating Crystal

8. 8 Rotating Crystal Technique

9. 9 The Rotating Crystal Technique was developed by Schiebold in 1919. Schematic Representation X-ray Tube Filter Collimating System Crystal mounted on a shaft Polychromatic X-ray Monochromatic X-ray Fine beam of parallel X-ray

10. 10 Now the shaft is moved to put the crystal into slow rotation about a fixed axis. This causes the sets of planes coming successively into their reflecting positions. When the angle value satisfies Bragg’s Equation a spot on the photographic plate is produced. Schematic Diagram

11. 11 One can take photographs in two ways : Complete Rotation Method – Occurs a series of complete revolutions. Each set of planes in the crystal diffracts four times during the rotation. These four diffracted beams are distributed into a rectangular pattern about the central point of the photograph. Outline of Photograph

12. 12 Oscillation Method – Crystal is oscillated through an angle of 15◦ or 20◦ Photographic plate is also moved back and froth with a same period Position of a spot on the plate indicates the orientation of the crystal Rotating Crystal Technique allows to measure the size of unit cell. Contd.

13. 13 XRD pattern is a plot of the intensity of X-rays scattered at different angles by a sample The detector moves in a circle around the sample The detector position is recorded as 2 θ The detector records number of X-rays observed at each 2θ X-ray intensity is recorded as “counts per second” or “counts”. XRD Plot

14. 14 Factors for peak height – Periodicity in one direction than other directions Preferred orientation of crystal Arrangement of crystal - Chaotic or random More electron density – Increased intensity of peak XRD Plot Interpretation X-axis = 2 θ Y-axis = Intensity of X- ray

15. 15 Powerful and rapid (< 20 min) technique for identification of an unknown sample In most cases, it provides an unambiguous sample structure determination Minimal sample preparation is required XRD units are widely available Data interpretation is relatively straight forward Pros

16. 16 Homogeneous and single phase material is best identified Must have access to a standard reference file of inorganic compounds Requires tenths of a gram of material which must be ground into a powder For unit cell determinations, indexing of patterns for non-isometric crystal systems is complicated Peak overlay may occur and worsens for high angle 'reflections' Cons

17. 17 Determining structure of crystals Polymer characterization Particle size determination Preferred orientation - Texture Phase identification Crystallite size and microstrain Percentage crystallinity calculation Miscellaneous applications Applications

18. 18 A is the X-ray pattern of one crystal B is the X-ray pattern of another crystal C is the X-ray pattern of excipient A+B+C will give a characteristic about the crystalline nature of all the three. Structure of Crystals A B C A+B+C

19. 19 XRD determines degree of crystallinity in a polymer Non- crystalline portion scatters x-ray beam to give a continuous background (amorphous material) Crystalline portion causes diffraction lines that are not continuous (crystalline material) Polymer Characterization Scatter from the instrument Scatter from amorphous material Pattern from crystalline material

20. 20 Where, v = volume or size of an individual crystallite V = total volume of specimen irradiated n = number of spots in a diffraction ring at a Bragg angle of θ Ø θ = divergence of X-ray beam and is a function of apparatus Generally a series of samples having particles of known sizes is used to obtain diffraction rings that may be compared with those from the unknown at similar values of θ . Particle Size Determination v = V× θ Ø ×cos θ / 2n

21. 21 Preferred orientation of crystallites can create a systematic variation in diffraction peak intensities Preferred Orientation (Texture)

22. 22 The diffraction pattern of every phase is as unique as our fingerprint Phases with same chemical composition can have drastically different diffraction patterns The position and the relative intensity of the peaks are compared to the reference patterns in database to get a knowledge of the phase volume ratio, in this case A , B , and C . Phase Identification A B C

23. 23 Crystallites smaller than 120nm create broadening of peaks Microstrain may also create peak broadening Analyzing the peak widths over a long range of 2 θ will let us separate the reason of broadening, microstrain or crystallite size. Crystallite Size and Microstrain

24. 24 The Crystallinity of sample is calculated by separating intensities due to amorphous and crystalline parts on diffraction. Percentage of Crystallinity can be calculated as ratio of Crystalline area to total area. Where, Xc = % Crystallinity Ac = Area of crystalline phase Aa = Area of amorphous phase Percentage Crystallinity Xc = Ac / (Ac + Aa)

25. 25 Determination of Cis – Trans isomerism State of anneal of metals Soil classification based on crystallinity Analysis of industrial dusts Assessment of weathering and degradation of natural and synthetic polymers Examination of factors promoting decay of tooth enamel and dentine Identification of effects of disease on bone structure Amount of crystalline matter present in sludge, etc. Miscellaneous

26. 26 Chatwal G R, Anand S K. Spectroscopy- Atomic and Molecular. Delhi; India: Himalaya Publishing House; 2018. Banerjee D. X-Ray Diffraction. IIT Kanpur; India: Tata McGraw Hills; 2017. Cullity B D, Stock S R. Elements of X-Ray Diffraction. Scotland; United Kingdom: Pearson; 2015. References

27. 27 Thank You