X ray diffraction analysis phase analysis

Xrd

1. Significance of peak shape in XRD pattern 1 . Peak position 2. Peak intensity 3. Peak width “ Shape and size of the unit cell” “ Atomic number and position of various atoms in the unit cell” “ Instrument parameter, temperature, crystal size, strain and the imperfections present”

2. Information in a Diffraction Pattern Phase Identification Crystal Size Crystal Quality Texture (to some extent) Crystal Structure Significance of peak shapes in XRD pattern Peak position Size and shape of unit cell Peak intensity atomic number and position of various atoms within the unit cell Peak width Instrument parameter, temperature, crystal size, strain and the imperfections present

3. Steps involved: Monochromatic x-ray interacts with the sample Detector moves in a circle around the sample Detector position is recorded as 2 θ Detector records x-rays received at each angle of 2 θ Intensity is measured either “counts” or “counts per sec” Θ - 2 Θ ( Bragg- Brentano) geometry is commonly used θ is adjusted to keep x-rays properly focused θ is adjusted either by rotating the crystal or by rotating the source Conversion of 2 θ to d- spacing allows identification of the compound and its structure θ d hkl d hkl d hkl d hkl

4. Step I Collect data Step 2 Analyse diffraction pattern with respect to peaks position, intensity and their width Step 3 Obtain Information (For desired specimen) θ Sequence of steps

5. Qualitative analysis of sample using X-ray diffraction Phase (single phase) identification and checking phase purity

6. Collect data for various angle (various position of detector) Phase identification

7. Intensity (a.u.) 2. Plot Intensity vs 2 Θ Phase identification

8. 2 (˚) d (Å) (I/I 1 )*100 27.42 3.25 10 31.70 2.82 100 45.54 1.99 60 53.55 1.71 5 56.40 1.63 30 65.70 1.42 20 76.08 1.25 30 84.11 1.15 30 89.94 1.09 5 Intensity ( a.u .) I 1 : Intensity of the strongest peak Phase identification 3. Convert the observed peak positions 2 θ into d hkl values using Bragg’s law  

9. Source of Information JCPDS (The Joint Committee on Powder Diffraction Standards) Or ICDD ( International Centre for Diffraction Data) JCPDS Card 4. Compare raw data with standard sources of data PDF contains collection of single phase XRD pattern in the form of tables of interplanar spacing (d), relative intensities, physical and crystallographic properties of the material Phase identification