Annealing Effect on Nickel Oxide Nanoparticles Properties

Abstract

Sodium hydroxide and nickel chloride have been used in the effective chemical precipitation process to create nickel oxide (NiO) NPs. We investigate how the morphological, structural, magnetic, and optical characteristics of nanocrystalline NiO are affected by annealing at temperatures of 300, 400, and 500 °C. Field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), and ultraviolet-visible (UV-vis) spectrophotometer have been utilized in order to characterize NiO-NPs. XRD pattern indicates the material's excellent crystallinity. At the same time, the FESEM study of the synthesized samples reveals that the annealing temperature has a considerable impact on the films' surface morphology. The average crystallite size of NiO samples falls within the range of 29–30.9 nm., whereas the average grain size of synthesized NiO-NPs, as determined by FESEM images, is between 25 and 29.6 nm. We demonstrate that as the annealing temperature rises, grains’ average size increases, but their shape remains  spherical. In addition to that, the UV-Vis spectroscopy analysis shows the particles’ significant absorption peak in the UV region. Our investigation reveals that the synthesized samples have direct band gaps. Before annealing, the energy gap measures 2.4 eV; however, by raising the annealing temperature, we were able to attain a broader range of band gap energies for NiO-NPs, with values spanning between 4.05 and 4.95 eV. The created NiO-NPs demonstrate superparamagnetic behavior, which was found in the VSM results examination.