X- Ray DiffractionPresentation By Archana M.Pharmacy (Pharmaceutics) GPRCP Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 1 CONTENTS INTRODUCTION GENERATION OF X-RAYS PRINCIPLE INSTRUMENTATION METHODS APPLICATIONS CONCLUSIONS REFERENCES Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 2 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 Max Von in crystals was discovered by Max von Laue. The Laue 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 Ch.Archana,M.Pharmacy(Pharmaceutics),Roll no:15 3 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 Pharmacy(Pharmaceutics).collimated to concentrate and directed towards the sample. Ch.M. These x-rays are generated by a cathode ray tube.PRINCIPLE X-ray diffraction is based on constructive interference of monochromatic x-rays and a crystalline sample.Archana.Roll no:15 5 . The interaction of incident rays with the sample produces constructive interference when conditions satisfy Bragg’s law. filtered to produce monochromatic radiation . BRAGG’s EQUATION Deviation = 2 Ray 1 Ray 2 d The path difference between ray 1 and ray 2 = 2d Sin For constructive Ch.M.Roll interference: n = 2d Sin no:15 6 .Archana.Pharmacy(Pharmaceutics). M. for constructive interference.Roll no:15 7 . nλ=2dsin this is called as BRAGG’S LAW Ch.Archana.Pharmacy(Pharmaceutics).“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”. M.Filter b.Counter methods Ch.Pharmacy(Pharmaceutics).Roll no:15 8 . INSTRUMENTATION Production of x-rays Collimator Monochromator a.Archana.Photographic methods b.Crystal monochromator Detectors a. Instrumentation of XRD Ch.M.Archana.Pharmacy(Pharmaceutics).Roll no:15 9 . Ch.Archana.PRODUCTION OF X-RAYS: X-rays are generated when high velocity electrons impinge on a metal target. Many types of x-ray tubes are available which are used for producing x-rays. The remainder being dissipated as heat.Roll no:15 10 .Pharmacy(Pharmaceutics).M. Approximately 1% of the total energy of the electron beam is converted into x-radiation. Coolidge tube b c a a .Roll no:15 11 . Battery to emit thermoionic electrons • C.M. 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 Ch.Pharmacy(Pharmaceutics). Positive voltage in the form of anode having a target a • b .Archana. 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.Pharmacy(Pharmaceutics).M. The collimator absorbs all the x-rays except the narrow beam that passes between the gap.COLLIMATOR: In order to get a narrow beam of x-rays. Ch.Roll no:15 12 .Archana. quartz etc.2 methods are available 1. TYPES OF MONOCHROMATORS In order to do monochromatization.Roll no:15 13 ..Archana.M. Ch.Filter 2.Pharmacy(Pharmaceutics).Crystal monochromator a)Flat crystal monochromator b)Curved crystal monochromator Materials used-Nacl. 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.Pharmacy(Pharmaceutics). A.Archana.M.Roll no:15 14 . Archana.Roll no:15 15 . Ch.•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 .Pharmacy(Pharmaceutics).M. quartz etc. 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.Roll no:15 16 .Pharmacy(Pharmaceutics).Archana.M. DETECTORS The x-ray intensities can be measured and recorded either by 1)Photographic methods 2)Counter methods a) Geiger . 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.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 .Archana.Pharmacy(Pharmaceutics). Dis advg: time consuming and uses exposure of several hours Ch.incident intensities I.M.Roll no:15 17 . 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 . COUNTER METHODS: a) Geiger .resulting in the production of avalanche of electrons that are travelling towards central anode Ch.Pharmacy(Pharmaceutics).Roll no:15 18 .M. Electon- central Production of anode X-RAY Collision with filling gas an ion pair Positive ion-moves to outer electrode The electron is accelerated by the potential gradient and causes the ionisation of large number of argon atoms .Archana. Pharmacy(Pharmaceutics).Archana.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.Roll no:15 19 .M. Archana. 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 . The dead time is short Ch.Roll no:15 20 .M. anthracene .napthalene and p-terphenol ixylene.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 .Pharmacy(Pharmaceutics). Archana.Pharmacy(Pharmaceutics).Roll no:15 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.M. Ch.M.Pharmacy(Pharmaceutics).Archana. q-tot charge collected on electrode. c-detector capacity.Roll no:15 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. Archana.Roll no:15 23 .Rotating crystal method 4. They are 1.Bragg’s X-ray spectrometer method 3.Pharmacy(Pharmaceutics).M.Laue’s photographic method a)Transmission method b)Back reflection method 2.X-RAY DIFFRACTION METHODS These are generally used for investigating the internal structures and crystal structures of various solid compounds.Powder method Ch. Archana.M.Pharmacy(Pharmaceutics).Roll no:15 24 . X-Ray Diffraction Method Laue Rotating Crystal Powder Orientation Lattice constant Lattice Parameters Single Crystal Single Crystal Polycrystal (powdered) Polychromatic Beam Monochromatic Beam Monochromatic Beam Fixed Angle Variable Angle Variable Angle Ch. •Also used in determination of symmetry of single crystals. The film intersects the cone.Archana.M. •Most suitable for the investigation of preferred orientation sheet particularly confined to lower diffraction angles. with the diffraction spots generally lying on an ellipse.Roll no:15 25 . One side of the cone of Laue reflections is defined by the transmitted beam.Pharmacy(Pharmaceutics). Ch. the film is placed behind the crystal to record beams which are transmitted through the crystal. •Can be used to orient crystals for solid state experiments. a)Transmission Laue method In the transmission Laue method. M. One side of the cone of Laue reflections is defined by the transmitted beam. This method is similar to Transmission method however. The film intersects the cone. with the diffraction spots generally lying on an hyperbola.b)Back-reflection method In the back-reflection method.Roll no:15 26 . The beams which are diffracted in a backward direction are recorded.Pharmacy(Pharmaceutics). the film is placed between the x-ray source and the crystal. Disadvantage: Big crystals are required Ch. black-reflection is the only method for the study of large and thick specimens.Archana. Crystal orientation is determined from the position of the spots. i. Each spot can be indexed.Pharmacy(Pharmaceutics).M. attributed to a particular plane. The Greninger chart is used for back-reflection patterns and the Leonhardt chart for transmission patterns.Roll no:15 27 . The Laue technique can also be used to assess crystal perfection from the size and shape Ch. using special charts.Archana.e. Kcl.M.and Zns-brags equation source 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.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.Roll no:15 28 .Archana.Pharmacy(Pharmaceutics). T Battery .Pharmacy(Pharmaceutics).M. while negative terminal is connected to quadrant electrometer(measures the strength of ionization current) Ch.Archana.Roll no:15 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. Archana.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.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.Pharmacy(Pharmaceutics).M. Ch.Roll no:15 30 . Ratio’s will be different for different crystals Experimentally observed ratio’s are compared with the calculated ratio’s .M.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.Archana.Pharmacy(Pharmaceutics).Roll no:15 31 .DETERMINATION OF CRYSTAL STRUCTURE BY BRAGG. Ch.particular structure may be identified. 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.Roll no:15 32 .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.ROTATING CRYSTAL METHOD: Photographs can be taken by : 1.Pharmacy(Pharmaceutics).Archana.M. M.Archana.Roll no:15 33 . Another fraction of grains will have another set of planes in the correct positions for the reflections to occur 3.Pharmacy(Pharmaceutics). Reflections are possible in different orders for each set Ch. Fine powder is struck on a hair with a gum . 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.it is suspended vertically in the axis of a cylindrical camera When monochromatic beam is allowed to pass different possibilities may happen 1. homogenized. The analyzed material is finely ground. and average bulk composition is determined. There will be some particles out of random orientation of small crystals in the fine powder 2. M.Archana.Roll no:15 34 .Pharmacy(Pharmaceutics). 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. APPLICATIONS OF XRD 1.Archana. Structure of crystals 5.Roll no:15 35 . Polymer methods to complexes characterisation a) Determination of cis- 3.Pharmacy(Pharmaceutics).Applications of diffraction 2. Particle size b) Determination of linkage determination isomerism a) Spot counting method 6.M.Miscellaneous applications b) Broadening of diffraction lines c) Low-angle scattering Ch. State of anneal in metals trans isomerism 4. 1.Archana.M.Pharmacy(Pharmaceutics).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 Ch.Roll no:15 36 . M.2.Archana.Roll no:15 37 .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.Pharmacy(Pharmaceutics).(crystalline materials) Ch. Roll no:15 38 . 4.State of anneal in metals:XRD is used to to test the metals without removing the part from its position and without weakening it.cosθ/2n V=volume of individual crystallite V=total volume irradiated n=no.Pharmacy(Pharmaceutics).M. of spots in diffraction ring δθ =divergence of x-ray beam Ch.Archana.PARTICLE SIZE DETERMINATION Spot counting method: v=V.3.δθ. Roll no:15 39 .Pharmacy(Pharmaceutics).Archana.M.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 Ch. Roll no:15 40 .M.Pharmacy(Pharmaceutics). 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 Ch.CONCLUSIONS For materials including metals.Archana. plastics. minerals. 41 .X-ray diffraction pattern for a single alum crystal. X-ray diffraction image of a crystal of lysozyme Ch.Archana.Pharmacy(Pharmaceutics).Roll no:15 42 .M. Pharmacy(Pharmaceutics).M.Archana.Roll no:15 43 .Ch. M.Ch.Pharmacy(Pharmaceutics).Archana.Roll no:15 44 . Bruker's X-ray Diffraction D8-Discover instrument . Timothy A.chatwal.Pharmacy(Pharmaceutics).332 4) http://www.page no:329-359 2)Principles of instrumental analysis.REFERENCES 1)Instrumental methods of chemical analysis .sharma.anand.f.sham k.303- 2.scienceiscool.5th edition .wikipedia.B.org/wiki/X-ray_crystallography Ch.org/solids/intro.Niemen.17th edition 1997-1998.Gurudeep R.Roll no:15 46 .M.skoog.GOEL publishing house.Archana.Himalaya publications page no:2.page no:277-298 3)Instrumental methods of chemical analysis .James holles.by Dougles a.html 5) http://en.K. Ch.M.Archana.Roll no:15 47 .Pharmacy(Pharmaceutics).