X-Ray Diffraction and Diffraction Methods BASICS

This presentation covers the basics of XRD and XRD methods. For more information, please refer the book which is mentioned in the references slide

1. Seminar On X – Ray Diffraction Technique and Diffraction Methods Melwin D’mello M.E (Welding Engineering) Centre for Materials Joining & Research (CEMAJOR), Department of Manufacturing Engineering, Annamalai University Presented by

2. CONTENTS Introduction Generation of X-ray X- ray region X- ray diffraction XRD Principle XRD Equipment Diffraction Methods Applications of XRD Methods References

3. INTRODUCTION X- rays were discovered by Wilhelm Roentgen who called them “X-rays” and it is also called as “Roentgen Rays”. X- ray diffraction was discovered by Max Von Laue in 1912. X- rays are electro magnetic radiation with wavelengths in the range 0.1 to 100 A o . X- rays used in diffraction experiments have typical wavelengths of 0.5 to 1.8 A o.

4. GENERATION OF X-RAYS

5. X - RAY REGION

6. X-RAY DIFFRACTION ( XRD ) These methods are based on the scattering of X-ray crystals. When x-rays interact with a solid material, the scattered beams causes diffraction.

7. XRD PRINCIPLE Different Planes in a crystal give different signals equal to positive interface of waves.

8. XRD EQIPMENT

9. EXPERIMENTAL DIFFRACTION METHODS

10. In this method a single crystal is held stationary in the path of radiation of continuous wavelength. While  is kept constant, the wavelength ,  is varied. A plane film receives the diffracted beams. A developed film after its exposure shows a diffraction pattern that consists of series of spots. 1. LAUE’S METHOD

11. Laue’s method is divided Into two types Transmission Method Back Reflection Method

12. a) Transmission Method A beam of x-ray is passed through the crystal, after passing through the crystal, x-rays are diffracted and recorded on a photographic plate.

13. a) Transmission Method

14. b) Back Reflection Method This method provides similar information as the transmission method.

15. 2. ROTATING CRYSTAL METHOD

16. Rotating Crystal Method cont … In this method , a single crystal is rotated about the fixed axis in a beam of monochromatic. The angle  is variable while the wavelength is kept constant. The variation of angle  due to rotation of the crystal brings different atomic planes in the crystal into position. To record such reflections a film is mounted on a cylindrical holder that is concentric with a rotating spindle.

17. This method is useful for samples that are difficult to obtain in single crystal form. The powder method is used to determine the value of the lattice parameters accurately. 3. POWDER METHOD

18. A sample of hundreds of powdered crystals show that the diffracted beams form continuous cones. A circle of film is used to record the diffraction pattern. Each cone intersects the film giving diffraction lines. The lines are seen as arcs on the film. The powder method cont …

19. APPLICATIONS OF XRD METHODS Determination of crystal size and shape. Particle size determination by spot counting methods. Crystallographic structural analysis. Unit cell calculations for crystalline materials. Identification of single and multi phase materials

20. REFERENCES “Instrumental Methods Of Chemical Analysis” by Gurudeep R Chatwal . https :// en.wikipedia.org/wiki/X-ray_crystallography

21. Thank you