Effect of Thermal Annealing on the Structural and Optical Properties of Nickel Oxide Nanoparticles

NiO nanoparticles were prepared by sol-gel method, which is one of the simplest and low-cost technique. In this work, the annealing effects on the crystal structure, vibration modes, purity and morphology were studied at different temperatures with different annealing times. X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy were used to determine the structure, crystallinity, and purity. Scanning electron microscopy (SEM) determined the nanoparticles to be spherical in shape with uniform sizes. Crystallite size of NiO nanoparticles has been calculated using Schemer formula. UV-VIS absorption spectroscopy determined the bandgap to be in the range of 3.2-3.44 eV. The stoichiometric variation with annealing was determined from energy dispersive x-ray analysis. The phonon and magnons observed in the Raman spectra show distinct size effects.