X-ray peak broadening analysis in ZnO nanoparticles

Abstract

Zinc oxide (ZnO) nanoparticles were synthesized by a hydrothermal process at 120 ∘C. XRD results reveal that the sample product is crystalline with a hexagonal wurtzite phase. TEM results confirm that the morphology of the annealed ZnO is rod shaped with an aspect ratio (length/diameter) of ∼3.2. We also investigate the crystallite development in nanostructured ZnO by X-ray peak broadening analysis. The individual contributions of small crystallite sizes and lattice strain to the peak broadening in as-prepared and annealed ZnO nanoparticles were studied using Williamson-Hall (W–H) analysis. All other relevant physical parameters including strain, stress and energy density value were calculated more precisely for all the reflection peaks of XRD corresponding to wurtzite hexagonal phase of ZnO lying in the range 20 ∘–65 ∘, from the modified form of W–H plot assuming the uniform deformation model (UDM), uniform stress deformation model (USDM) and uniform deformation energy density model (UDEDM). The root mean square (RMS) lattice strain 〈 ε R M S 〉 calculated from the interplanar spacing and the strain estimated from USDM and UDEDM are different due to consideration of anisotropic crystal nature. The results obtained show that the mean particle size of ZnO nanoparticles estimated from TEM analysis, Scherer’s formula and W–H method are highly inter-correlated. All the physical parameters from W–H plot are tabulated, compared, and found to match well with the value of bulk ZnO.