Analysis of AC electrical properties of nanocrystalline nickel oxide

Nanocrystalline nickel oxide (NiO) having an average particle size of 2–3 nm was prepared through a wet chemical route. The electrical properties of pellets of the nanoparticles were studied as a function of the frequency of the applied AC signal and temperature. The article presents a qualitative discussion of the various relaxation processes active in the grain interior and grain boundary of the nanocrystalline NiO as inferred from the analysis of the AC electrical response in ρ∗ and ε∗ planes. The time constants for both the relaxation processes exhibit a distribution in values and their temperature dependence is markedly different from each other. The high values of ε′ and ε″ at low frequencies is attributed to the possible dielectric amplification due to the presence of conducting grain boundaries covering insulating grains.