X-ray peak broadening studies of nanocrystalline hydroxyapatite by Williamson–Hall analysis

Hydroxyapatite (HA) nanoparticles were prepared by microwave synthesis method and the obtained powder is annealed at 800 °C for 2 h. The annealed HA particles were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy methods. The HA size and morphology were examined using a transmission electron microscope (TEM). The XRD results reveal that the diffraction peaks of the annealed HA were of well crystalline and correspond to the hexagonal crystal structure. The XRD and FTIR results confirm the absence of secondary phases such as β-tricalcium phosphate (β-TCP) and calcium oxide in annealed HA particles. The TEM result confirms the hexagonal structure of annealed HA and the particles were observed to be of ellipsoid-like shaped morphology with less agglomeration. The lattice strain, crystallite size, lattice deformation stress and deformation energy density for annealed (800 °C) HA nanoparticles were estimated by Williamson–Hall-isotropic strain model (W–H-ISM), W–H-anisotropic strain model (W–H-ASM) and W–H-energy density model (W–H-EDM) based on Williamson–Hall (W–H) plot from powder X-ray diffraction data. The results of estimated average crystallite size of annealed HA by Scherrer and W–H plot methods were compared with TEM results. It is found that the average crystallite size measured by W–H plot methods is in good agreement with TEM results.