Temperature-dependent analysis of dielectric behaviour of Co3O4/NiO nanocomposites with varying NiO concentration

In the present study, we report the dielectric, impedance, modulus and conductivity study of Co3O4, NiO & Co3O4-NiO nanocomposites with varying NiO concentration (10%, 40%). XRD analysis suggests crystalline phases of pure NiO, Co3O4 and the nanocomposite samples. The crystallite size was calculated using SSP method. The analysis of experimental results indicate that dielectric constant (epsilon '), dielectric loss factor (tan delta) and a.c. conductivity sigma(ac)(omega) are temperature, frequency and concentration dependent. It was found that while dielectric constant is an increasing function of temperature, it decreases with increasing frequency. The activation energy (E-a) of the ac conduction have been found between 0.085 and 0.13 eV for all the samples. To discuss the conduction mechanism, the AC conductivity and temperature dependence of frequency exponent 's' have been analysed based on Correlated Barrier Hopping (CBH) and Non-Overlapping Small Polaron tunneling (NSPT) model. Simultaneously, correlated AC conductivity data with CBH & NSPT model were used to calculate the value of maximum barrier height (binding energy) (W-m), AC activation energy, tunnelling distance (R-w) and density of states at Fermi level N (E-F). The Nyquist plot from complex impedance spectrum shows only one semicircular arc representing the grain boundary effect in the electrical conduction. The modulus mechanism indicates the non-Debye type of conductivity relaxation in the material, which is supported by impedance data. The variation of AC conductivity as function of temperature indicates that the conduction is due to thermally activated charge carriers.