Effect of microstrain on the crystallite size of ZnO nanoparticles: X-ray peak profile and Rietveld analysis

Crystallite size is an important parameter that can be easily calculated from the X-ray diffraction pattern. However, the diffraction peaks may shift and broaden due to change in particle size caused by dislocations and strain in the crystal. We have used the Rietveld analysis to evaluate the lattice parameters of the wurtzite ZnO nanoparticles. Crystallite size was initially calculated from Scherrer formula. In Scherrer method the broadening was not included, but W-H method, UDM, USDM, UDEDM consider the peak broadening due to lattice strain and anisotropy. The crystallite size calculation by the later three methods give almost same result (41.58 nm, 41.48 nm and 42.48 nm). The crystallite size calculated using the SSP method was 41.2 nm which is very close to the other three methods. Our findings suggest that microstrain can impact on the calculated crystallite size using various methods.