Nickel hydroxide (beta-Ni(OH)(2)) and nickel oxyhydroxide (beta-NiOOH) nanoparticles assigned as P and PO, respectively, were successfully synthesized through a microwave-assisted oxidation technique using sodium hydroxide as the precipitating agent and sodium hypochlorite as the oxidizing agent. NiO nanoparticles were then obtained by thermal decomposition of nickel oxyhydroxide (PO) compound. The effect of the parameters such as concentration of the precipitating agent and calcination temperature on the structural characteristics of the products was investigated. The as-prepared materials were well characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetry (TGA), and scanning electron microscopy (SEM) analytical techniques. XRD and SEM results indicated that the crystallinity and particle size of the products depend on NaOH concentration and calcination temperature. (c) 2013 Elsevier B.V. All rights reserved.