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Basics of X-Ray Diffraction Self-User Training for the X-Ray Diffraction

Basics of X-Ray Diffraction Self-User Training for the X-Ray Diffraction. R. Shanmuga Selvan Research Scholar PRIST University Thanjavur. Basics of Diffraction. History: Wilhelm Conrad Röntgen.

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Basics of X-Ray Diffraction Self-User Training for the X-Ray Diffraction

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  1. Basics of X-Ray DiffractionSelf-User Training for the X-Ray Diffraction R. Shanmuga Selvan Research Scholar PRIST University Thanjavur

  2. Basics of Diffraction

  3. History: Wilhelm Conrad Röntgen Wilhelm Conrad Röntgen discovered 1895 the X-rays. 1901 he was honoured by the Noble prize for physics. In 1995 the German Post edited a stamp, dedicated to W.C. Röntgen

  4. The Principles of an X-ray Tube

  5. The Generating of X-rays

  6. The Generating of X-rays • Emission Spectrum of a Molybdenum X-Ray Tube • Bremsstrahlung = continuous spectra • characteristic radiation = line spectra

  7. You can use XRD to determine • Phase Composition of a Sample • Quantitative Phase Analysis: determine the relative amounts of phases in a mixture by referencing the relative peak intensities • Unit cell lattice parameters and Bravais lattice symmetry • Index peak positions • Lattice parameters can vary as a function of, and therefore give you information about, alloying, doping, solid solutions, strains, etc. • Residual Strain (macrostrain) • Crystal Structure • By Rietveld refinement of the entire diffraction pattern • Epitaxy/Texture/Orientation • Crystallite Size and Microstrain • Indicated by peak broadening • Other defects (stacking faults, etc.) can be measured by analysis of peak shapes and peak width • We have in-situ capabilities, too (evaluate all properties above as a function of time, temperature, and gas environment)

  8. Powder Diffraction Diffractogram

  9. Powder diffraction data consists of a record of photon intensity versus detector angle 2q. • Diffraction data can be reduced to a list of peak positions and intensities • Each dhkl corresponds to a family of atomic planes {hkl} • individual planes cannot be resolved- this is a limitation of powder diffraction versus single crystal diffraction Raw Data Reduced dI list

  10. Identification of Unknown via x-ray Diffraction Technique To identify the unknown specimen using JCPDS Card • Formula nλ = 2d Sinθ d = nλ /2 Sinθ • Procedure • Calculate the d-shaping for each reflection • Identify 10 most intense peak name it d1 d2 d3 etc. • Open JCPDS search using long lines in Misc option • Once matched all peaks, compare relative intensities with tabulated values. • When the experimental d-shaping and intensities for the most intense reflections match those in the card, get the JCPDS card and compare for all reflections. Once all agree, match the pattern and identify the unknown

  11. Step 2 Result The given XRD data is well matched with the JCPDS card no:….. The material is :…………………………..

  12. Determination of Lattice Parameter • To calculate the lattice parameter of given XRD pattern and compare value with given JCPDS cards. • Formula Given pattern is of ---------------- crystal system. Then the lattice conditions will be------------. Appropriate interlayer spacing formula--------------- • Procedure • Collect an XRD pattern and calculate the d-shacing /2θfor each reflection. • Locate proper d1 grouping in Hanawalt (numerical) search manual. • MATCH d1;look for match to d2 & d3. • Once all three match, compare relative intensities with tabulated values. • When the experimental d spacing and intensities for the most intense reflections match. Those in the hanwalt manual, get the JCPDS card and compare for all reflections. Once all agree you will have to match the pattern and identify the unknown.

  13. Determination of Lattice Parameter Result The calculated lattice parameter for given XRD data is ………….. It well matched with the lattice parameter given in JCPDS card No:…………. The lattice parameter of ……………….

  14. Determination of Crystallite Size D= grain diameter β= peak width in radians at FWHM K= 0.9 to 1.0 depending upon grain shape Note most of the time K consider as 0.9

  15. Lattice strain calculation • Get straight line w/slope ≈ the lattice strain. Procedure • Collect and index diffraction patterns • Well annealed specimen • Deformed specimen • In well annealed specimen, calculate FWHM for each reflection. • Calculate βcosθ and polt versus sinθ.

  16. Available Free Software • GSAS- Rietveld refinement of crystal structures • FullProf- Rietveld refinement of crystal structures • Rietan- Rietveld refinement of crystal structures • PowderCell- crystal visualization and simulated diffraction patterns • JCryst- stereograms

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