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X ray diffraction.pptx
- 1. COURSE TITLE NANO SCIENCE & TECHNOLOGY COURSECODE: PHY-608 DR. SHAISTA RAFIQUE 1
- 3. GROUP#9 Sabika Zainab Uswa Ismail Maryam Nighat 2 26 34 Muqaddas Ghafoor 44 Shehr Bano 48 Samra Sha Jahan 100 Zartasha Rasheed 104 Fizza Fatima 122 3
- 4. X-ray Diffraction: • X-ray diffraction analysis (XRD) is a technique used in material science to determine the crystallographic structure of a material. XRD works by irradiating a material with incident X-rays and then measuring the intensities and scattering angles of the X-rays that leave the material. • XRD has been used extensively for the examination of materials and thin films. Its effective use depends upon having a crystalline material. The technique is a bulk sensitive analytical method, but can be used to provide information relevant to surface changes in suitable circumstances 4
- 5. X-ray Diffraction Principle: • X-ray diffraction is based on constructive interference of monochromatic X-ray and a crystalline sample. These X-rays are generated by a cathode ray tube, filtered to produce monochromatic radiation, collimated to concentrate and directed towards the sample How does XRD works: • Crystals are regular arrays of atoms, whilst X-rays can be considered as waves of electromagnetic radiation. Crystal atoms scatter incident X-rays, primarily through interaction with the atoms. This phenomenon is known as elastic scattering; the electron is known as the scatterer. A regular array of scatters produces a regular array of spherical waves. 5
- 6. 2d sinθ = nλ • Where d is the spacing between diffracting planes, θ is the incident angle, n is an integer, and λ is the beam wavelength. The specific directions appear as spots on the diffraction pattern called reflections. • Consequently, X-ray diffraction patterns result from electromagnetic waves impinging on a regular array of scatterers. Bragg’s Law and Diffraction 6
- 7. The phenomenon of x-ray diffraction is useful for the determination of structure of solid. Bragg’s law is widely used for both these applications. For applying Bragg’s law for crystal structure determination. It is required that λ and θ must be matched properly. Three methods are generally adopted for the study of crystal structure. 1. Laue Method 2. Rotating Crystal method 3. Powder method X-ray Diffraction Methods 7
- 8. Laue Method: • Used for the study of crystal structure and is mostly used for determination of Crystal symmetry. • A beam of polychromatic X-rays of wavelengths ranging from 0.2Å to 2Å is allowed to fall on a small crystal of dimension 1 mm * 1mm * 1mm, placed on a goniometer. • Generally, the beam is allowed to fall perpendicular to the plane of the crystal under study. While passing through the crystal. • 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. 8
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- 10. Rotating Crystal Method: • 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. • A photographic plate is attached inside the cylindrical holder along with its surface. It may be noted that generally the vertical Axis is taken as the rotation axis. 10
- 11. Powder Crystal Method: Bragg’s method and the rotating Crystal Method required the precise mounting of a single crystal on a certain crystal Axis. Which is a tedious task to do. To overcome this difficulty powder crystal method is used. • Prepare a powdered sample of the crystalline material. • Mount the powder on a sample holder. • Use an X-ray diffractometer to direct X-rays at the sample. • Capture the diffracted X-rays with a detector, creating a diffraction pattern. • Analyse the diffraction pattern to extract information about the crystal structure. 11
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- 13. XRD Analysis: X-ray diffraction (XRD) analysis produces characteristic peaks in a diffraction pattern, which provide valuable information about the crystal structure of a material. Here's what these peaks can reveal: 1. Crystal Structure: The positions and intensities of the diffraction peaks correspond to the arrangement of atoms within the crystal lattice. By comparing the observed peak positions with known crystal structures in a database, it is possible to identify the crystal structure of the material under analysis. 2. Lattice Parameters: The positions of the diffraction peaks allow for the determination of the lattice parameters, such as the unit cell dimensions (a, b, c) and angles (α, β, γ). These parameters describe the size and shape of the crystal lattice. 13
- 14. XRD Analysis: 3. Crystal Orientation: The orientation of the crystal lattice relative to the sample surface can be determined by analysing the angles at which the diffraction peaks occur. This information is particularly useful in the field of texture analysis, where the preferred orientation of crystalline materials is investigated. 4. Crystalline Phases: Different crystalline phases within a sample can be identified based on their unique diffraction patterns. By comparing the observed peaks with reference patterns of known phases, it is possible to determine the presence of multiple phases and their relative proportions in a sample. 5. Crystallite Size and Strain: The width and shape of the diffraction peaks provide insights into the crystallite size and strain within a material. Broadened or asymmetric peaks indicate smaller crystallite sizes and higher levels of internal strain or defects. 14
- 15. • In this figure of XRD Analysis, Pristine and Calcinated Biochar results are given. • Pristine is grinded Crab Shell particles and CB 900 shows its calcination at 9000C. • Calcite and Lime peaks can be observed from XRD Analysis. X-rays Diffraction (XRD) Analysis Example: 15
- 16. Example: • This figure shows the XRD pattern of PPy/Cu NPs (Polypyrrole Copper Nanoparticles) films deposited on stainless steel substrates (different electrodes). • The peak attributed to 43.5, 50, and 74 is of stainless-steel rest peaks observed are of Cu nanoparticles. In addition, the peaks of Cu NPs are overlapped on the peaks of stainless-steel substrate. 16
- 17. • XRD is a non-destructive technique to identify crystalline phases and orientation • Obtain XRD pattern ; Measure d-spacings ; Obtain integrated intensities ; Compare data with known standards in the JCPDS file • To determine structural properties: • Lattice parameters (10-4Å), grain size, expitaxy, phase composition, prefer strained orientation (Laue) order-disorder transformation, thermal expansion • To measure thickness of thin films and multi-layers • To determine atomic arrangement Applications: 17
- 18. • The electron density and accordingly, the position of the atoms in complex structures, such as penicillin may be determined from a comprehensive mathematical study of the x-ray diffraction pattern. • The elucidation of structure of penicillin by XRD paved the way for the later synthesis of penicillin. • The powder XRD pattern may be thought of as finger print of the single crystal structure, and it may be used conduct qualitative and quantitative analysis. • XRD can also be used to determine whether the compound is solvated or not Applications: 18
- 19. Instrumental Sources of Error: • Specimen displacement • Instrument misalignment • Error in zero 2θ Position • Peak distortion due to K alfa 2 and K beta wavelengths 19
- 20. Conclusions: • Non-destructive, fast, easy sample preparation • High-accuracy for d-spacing calculations • Can be done in-situ • Single crystal, poly, and amorphous materials • Standards are available for thousands of material systems 20
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