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  • Light and its nature have caused a lot of ink to flow during these last decades. Its dual behavior is partly explained by (1)Double-slit experiment of Thomas Young - who represents the photon’s motion as a wave - and also by (2)the Photoelectric effect in which the photon is considered as a particle. A Revolution: SALEH THEORY solves this ambiguity and this difficulty presenting a three-dimensional trajectory for the photon's motion and a new formula to calculate its energy. More information on :
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  1. 1. X- Ray Diffraction Presentation By Archana M.Pharmacy (Pharmaceutics) GPRCP 1 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  3. 3. INTRODUCTION: X-rays were discovered by Wilhelm Roentgen who called them x-rays because the nature at first was unknown so, x-rays are also called Roentgen rays. X-ray diffraction in crystals was discovered by Max von Laue. The wavelength range is 10-7 to about 10-15 m. The penetrating power of x-rays depends on energy also, there are two types of x-rays. i) Hard x-rays: which have high frequency and have more energy. ii) soft x-rays: which have less penetrating and have low energy Max Von Laue 3 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  4. 4. X-RAYS 1.X-rays are short wave length electromagnetic radiations produced by the deceleration of high energy electrons or by electronic transitions of electrons in the inner orbital of atoms 2.X-ray region 0.1to100 A˚ 3.Analytical purpose 0.7 to 2 A˚ Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 4
  5. 5. PRINCIPLE X-ray diffraction is based on constructive interference of monochromatic x-rays 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. The interaction of incident rays with the sample produces constructive interference when conditions satisfy Bragg’s law. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 5
  6. 6. BRAGG’s EQUATION d     Ray 1 Ray 2  Deviation = 2  The path difference between ray 1 and ray 2 = 2d Sin  For constructive interference: n = 2d Sin 6 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  7. 7. “Constructive interference of the reflected beams emerging from two different planes will take place if the path lengths of two rays is equal to whole number of wavelengths”. for constructive interference, nλ=2dsin this is called as BRAGG’S LAW 7 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  8. 8. INSTRUMENTATION  Production of x-rays  Collimator  Monochromator a.Filter b.Crystal monochromator  Detectors a.Photographic methods b.Counter methods 8 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  9. 9. Instrumentation of XRD Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 9
  10. 10. PRODUCTION OF X-RAYS: X-rays are generated when high velocity electrons impinge on a metal target. Approximately 1% of the total energy of the electron beam is converted into x-radiation. The remainder being dissipated as heat. Many types of x-ray tubes are available which are used for producing x-rays. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 10
  11. 11. Coolidge tube  a . Positive voltage in the form of anode having a target a • b . Battery to emit thermoionic electrons • C. Cathode –filament of tungsten metal • The electrons are accelerated towards the target a • On striking the target the electrons transfer their energy to its metallic surface which gives off x-ray radiation 11 b c a Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  12. 12. COLLIMATOR:  In order to get a narrow beam of x-rays, the x-rays generated by the target material are allowed to pass through a collimator which consists of two sets of closely packed metal plates separated by a small gap.  The collimator absorbs all the x-rays except the narrow beam that passes between the gap. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 12
  13. 13. TYPES OF MONOCHROMATORS 13 In order to do monochromatization,2 methods are available 1.Filter 2.Crystal monochromator a)Flat crystal monochromator b)Curved crystal monochromator Materials used-Nacl,quartz etc,. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  14. 14. A.FILTER: X-ray beam may be partly monochromatized by insertion of a suitable filter A filter is a window of material that absorbs undesirable radiation but allows the radiation of required wavelength to pass Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 14
  15. 15. •2)CRYSTAL MONOCHROMATOR : Crystal monochromators is made up of suitable crystalline material positioned in the x-ray beam so that the angle of reflecting planes satisfied the Bragg’s equation for the required wavelength the beam is split up into component wavelengths crystals used in monochromators are made up of materials like Nacl, lithium fluoride , quartz etc. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 15
  16. 16. DETECTORS  The x-ray intensities can be measured and recorded either by  1)Photographic methods  2)Counter methods  a) Geiger - Muller tube counter  b) Proportional counter  c) Scintillation detector  d) Solid state semi conductor detector  e) Semi conductor detectors  Both these types of methods depends upon ability of x-rays to ionize matter and differ only in the subsequent fate of electrons produced by the ionizing process. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 16
  17. 17.  Photographic method: To record the position and intensity of x-ray beam a plane or cylindrical film is used  The film after exposing to x-ray is developed  The blackening of the developed film is expressed in terms of density units D given by D=log I₀/I I₀- incident intensities I- transmitted intensities D-Total energy that causes blackening of the film D is measured by densitometer The photographic method is mainly used in diffraction studies since it reveals the entire diffraction pattern on a single film . Dis advg: time consuming and uses exposure of several hours Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 17
  18. 18.  COUNTER METHODS:  a) Geiger - Muller tube counter Geiger tube is filled with inert gas like argon Central wire anode is maintained at a positive potential of 800 to 2500V . X-RAY Collision with filling gas Production of an ion pair Electon-central anode Positive ion-moves to outer electrode The electron is accelerated by the potential gradient and causes the ionisation of large number of argon atoms ,resulting in the production of avalanche of electrons that are travelling towards central anode Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 18
  19. 19. b)PROPORTIONAL COUNTER:  Construction is similar to Geiger tube counter  Proportional counter is filled with heavier gas like xenon and krypton  Heavier gas is preferred because it is easily ionized  Operated at a voltage below the geiger plateau  The dead time is very short (~0.2μs), it can be used to count high high rates without significant error. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 19
  20. 20. C)SCINTILLATION DETECTOR:  In a scintillation detector there is large sodium iodide crystal activated with a small amount of thallium  When x-ray is incident upon crystal , the pulses of visible light are emitted which can be detected by a photo multiplier tube  Useful for measuring x-ray of short wavelength  Crystals used in scintillation detectors include sodium iodide , anthracene ,napthalene and p-terphenol ixylene.  The dead time is short Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 20
  21. 21. d)Solid state semi-conductor detector  In this type of detector ,the electrons produced by x-ray beam are promoted into conduction bands and the current which flows is directly proportional to incident x-ray energy  Dis advantage:  Semi – conductor device should be maintained at low temperatures to minimize noise and prevent deterioration Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 21
  22. 22. e)semi-conductor detectors:  When x-ray falls on silicon lithium drifted detector an electron (-e) and a hole (+e)  Pure silicon made up with thin film of lithium metal plated onto one end  Under the influence of voltage electrons moves towards +ve charge and holes towards –ve  Voltage generated is measure of the x-ray intensity falling on crystal  Upon arriving at lithium pulse is generated  Voltage of pulse=q/c; q-tot charge collected on electrode, c-detector capacity. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 22
  23. 23. X-RAY DIFFRACTION METHODS These are generally used for investigating the internal structures and crystal structures of various solid compounds. They are 1.Laue’s photographic method a)Transmission method b)Back reflection method 2.Bragg’s X-ray spectrometer method 3.Rotating crystal method 4.Powder method Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 23
  24. 24. X-Ray Diffraction Method Laue Rotating Crystal Powder Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 24 Orientation Single Crystal Polychromatic Beam Fixed Angle Lattice constant Single Crystal Monochromatic Beam Variable Angle Lattice Parameters Polycrystal (powdered) Monochromatic Beam Variable Angle
  25. 25. 25 a)Transmission Laue method In the transmission Laue method, the film is placed behind the crystal to record beams which are transmitted through the crystal. One side of the cone of Laue reflections is defined by the transmitted beam. The film intersects the cone, with the diffraction spots generally lying on an ellipse. •Can be used to orient crystals for solid state experiments. •Most suitable for the investigation of preferred orientation sheet particularly confined to lower diffraction angles. •Also used in determination of symmetry of single crystals. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  26. 26. b)Back-reflection method  In the back-reflection method, the film is placed between the x-ray source and the crystal. The beams which are diffracted in a backward direction are recorded.  One side of the cone of Laue reflections is defined by the transmitted beam. The film intersects the cone, with the diffraction spots generally lying on an hyperbola.  This method is similar to Transmission method however, black-reflection is the only method for the study of large and thick specimens.  Disadvantage:  Big crystals are required 26 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  27. 27.  Crystal orientation is determined from the position of the spots. Each spot can be indexed, i.e. attributed to a particular plane, using special charts.  The Greninger chart is used for back-reflection patterns and the Leonhardt chart for transmission patterns.  The Laue technique can also be used to assess crystal perfection from the size and shape Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 27
  28. 28. The Bragg’s x-ray spectrometer method:  Laue-beam of x-ray-crystal-emitted x-ray obtained on photographic plate-using photograph-brag analysed structures of crystals of Nacl,Kcl,and Zns-brags equation  Single plane generates several diffraction lines-sum tot of diffraction lines gives diffraction patterns-from the pattern we can deduce different distances between planes-angle between planes in each of three dimensions Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 28 source
  29. 29. The Bragg’s x-ray spectrometer method:  A-anti cathode  B-B’ – Adjustable slits  C-crystal  E-ionization chamber  One plate of ionization chamber is connected to the positive terminal of a H.T Battery , while negative terminal is connected to quadrant electrometer(measures the strength of ionization current) Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 29
  30. 30. The Bragg’s x-ray spectrometer method Working:  Crystal is mounted such that ѳ=0° and ionization chamber is adjusted to receive x-rays  Crystal and ionization chamber are allowed to move in small steps  The angle through which the chamber is moved is twice the angle through which the crystal is rotated  X-ray spectrum is obtained by plotting a graph between ionization current and the glancing angleѳ  Peaks are obtained.peaks corresponds to Bragg’s reflection  Different order glancing angles are obtained with known values of d and n and from the observed value of ѳ , λ can be measured. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 30
  31. 31. DETERMINATION OF CRYSTAL STRUCTURE BY BRAGG,S LAW  X-Rays falls on crystal surface  The crystal is rotated and x-rays are made to reflect from various lattice planes  The intense reflections are measured by bragg’s spectrometer and the glancing angles for each reflection is recorded  Then on applying bragg’s equation ratio of lattice spacing for various groups of planes can be obtained.  Ratio’s will be different for different crystals  Experimentally observed ratio’s are compared with the calculated ratio’s ,particular structure may be identified. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 31
  32. 32. ROTATING CRYSTAL METHOD: Photographs can be taken by :  1.Complete rotation method:in this method series of complete revolutions occur  Each set of a plane in a crystal diffracts four times during rotation  Four diffracted beams are distributed into a rectangular pattern in the central point of photograph  2.Oscillation method:the crystal is oscillated at an angle of 15° or 20°  The photographic plate is also moved vack and forth with the crystal  The position of the spot on the plate indicates the orientation of the crystal at which the spot wasformed Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 32
  33. 33. POWDER CRYSTAL METHOD: 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. Fine powder is struck on a hair with a gum ,it is suspended vertically in the axis of a cylindrical camera  When monochromatic beam is allowed to pass different possibilities may happen 1. There will be some particles out of random orientation of small crystals in the fine powder 2. Another fraction of grains will have another set of planes in the correct positions for the reflections to occur 3. Reflections are possible in different orders for each set Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 33
  34. 34.  If the angle of incidence is ѳ then the angle of reflection will be 2ѳ  If the radius is r the circumference 2πr corresponds to a scattering angle of 360° Ѳ=360*1/πr  From the above equation the value of ѳ can be calculated and substituted in bragg’s equation to get the value of d  Applications  Useful for determining the complex structures of metals and alloys  characterization of crystalline materials  identification of fine-grained minerals such as clays and mixed layer clays that are difficult to determine optically  determination of unit cell dimensions  measurement of sample purity Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 34
  35. 35. APPLICATIONS OF XRD 1. Structure of crystals 2. Polymer characterisation 3. State of anneal in metals 4. Particle size determination a) Spot counting method b) Broadening of diffraction lines c) Low-angle scattering 5.Applications of diffraction methods to complexes a) Determination of cis-trans isomerism b) Determination of linkage isomerism 6.Miscellaneous applications 35 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  36. 36. 1.STRUCTURE OF CRYSTALS a-x-ray pattern of salt Nacl b-x-ray pattern of salt Kcl c-x-ray pattern of mixture of Nacl &Kcl d-x-ray pattern of a powder mixed crystal of Nacl & Kcl 36 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  37. 37. 2.POLYMER CHARACTERISATION  Determine degree of crystanillity  Non-crystalline portion scatters x-ray beam to give a continuous background(amorphous materials)  Crystalline portion causes diffraction lines that are not continuous.(crystalline materials) 37 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  38. 38. 38 3.State of anneal in metals:XRD is used to to test the metals without removing the part from its position and without weakening it. 4.PARTICLE SIZE DETERMINATION Spot counting method: v=V.δθ.cosθ/2n V=volume of individual crystallite V=total volume irradiated n=no. of spots in diffraction ring δθ =divergence of x-ray beam Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  39. 39. MISCELLANEOUS APPLICATIONS  Soil classification based on crystallinity  Analysis of industrial dusts  Assessment of weathering & degradation of minerals & polymers  Study of corrosion products  Examination of tooth enamel & dentine  Examination of bone state & tissue state  Structure of DNA&RNA 39 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  40. 40. CONCLUSIONS  For materials including metals, minerals, plastics, pharmaceuticals and semiconductors XRD apparatus provide highly accurate tools for non-destructive analysis.  The diffraction systems are also supported by an extensive range of application software 40 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  41. 41. X-ray diffraction pattern for a single alum crystal. 41
  42. 42. X-ray diffraction image of a crystal of lysozyme 42 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  43. 43. 43 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  44. 44. 44 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  45. 45. Bruker's X-ray Diffraction D8-Discover instrument
  46. 46. REFERENCES 1)Instrumental methods of chemical analysis ,B.K.sharma,17th edition 1997-1998,GOEL publishing no:329-359 2)Principles of instrumental analysis,5th edition ,by Dougles a.skoog,f.James holles,Timothy no:277-298 3)Instrumental methods of chemical analysis ,Gurudeep R.chatwal,sham k.anand,Himalaya publications page no:2.303- 2.332 4) 5) 46 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15
  47. 47. Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 47