Structural and dielectric properties of NiO nanoparticles

NiO nanoparticles were prepared by wet chemical precipitation and dielectric, AC conductivity, and impedance properties were studied by complex impedance spectroscopy as a function of frequency at different temperatures. Non-stoichiometric sample (Ni40O60) shows diffraction peaks corresponding to cubic NiO and near stoichiometric sample (Ni48O52) was found to be amorphous. Stoichiometry of NiO nanoparticles was determined using EDS analysis. The estimated dielectric constant was found to be 35 and 40 for Ni40O60 and Ni48O52 nanoparticles. Loss peak shifts to the higher frequency which is due to long range hopping of charge carriers. Impedance analysis reveals Debye type relaxation process. The presence of two semicircular arcs in Nyquist plot explains that the grain and grain boundary conduction prevails in the sample. Nyquist plot shows that NiO nanoparticles possess negative temperature coefficient of resistance (NTCR). The variation of AC conductivity as function of temperature indicates that the conduction is due to thermally activated charge carriers. (C) 2012 Elsevier B.V. All rights reserved.