Determination of crystallite size of a polycrystalline sample using X-ray diffraction
The following steps are generally used for the estimation of crystallite size
- Peak identification: from the XRD plot (I Vs 2θ), diffraction peaks are identified and corresponding 2θ values are noted.
- Calculation of FWHM: Full-width half maxima of the selected peaks is determined by measuring the width of the peak at half of its maximum intensity
Application of Scherrer equation: Using the following equation, crystallite size (D) is obtained by averaging the values of multiple peaks.
D=Kλ/βCosθ
Where λ is X-ray wavelength, β (FWHM) is in radians, and the value of K (Scherrer constant) varies between 0.62-2.08 (commonly used as 0.9). It may be noted that peak-broadening may arise from instrument due to variation in wavelength, eucentric height, slit size, etc. Therefore, the peak-broadening of the sample must exclude the instrumental peak-broadening while calculating the crystallite size (D) as per the equation:
