The present work reports the synthesis and characterization of cobalt oxide nanoparticles. Microwave oven method was used for synthesizing cobalt oxide nanoparticles. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy, photoluminescence (PL) and scanning electron microscope (SEM). The prepared samples show poor crystalline nature so that the samples were calcined at 300 °C for 1 hr. The calcined samples were characterized for further changes in its morphology. XRD identifies the sample is in Co₃O₄ phase with face-centered cubic structure. Debye-Scherer formula was used to calculate the average crystallite size of the annealed sample and it was found to be 7 to 28 nm. In addition to crystallite size, specific surface area, dislocation density and microstrain are calculated using XRD. Williamson-Hall plot was used to calculate the size and strain. FT-IR spectrum shows two stretching bands at 660 and 550 cm⁻¹ which confirm the functional group present in the cobalt oxide nanoparticles. In optical absorption studies, a blue shift in the energy band gap reveals the quantum confinement effect. Photoluminescence spectra shows emission peak in the visible region.

Keywords: Cobalt Oxide; Supercapacitor; Microwave; Williamson-Hall Plot;