Temperature and frequency dependent dielectric relaxation of Ni-Fe-Oxide nanocomposites

Nickel-iron Oxides powder with different molar ratios of Ni:Fe are successfully synthesized by easy facile glycol mediated sol-gel auto-combustion synthesis process. Influence of compositional molar percentage variation on structural, dielectric and charge transport mechanism has been studied. The change of average crystallite size from 26 nm to 8 nm of these nickel iron powder samples has been observed with the change of Ni:Fe molar ratios. The dielectric constant and loss factor of all these materials show strong temperature dependence at all frequencies. The nanocomposites exhibit high dielectric constant and relatively low dielectric loss which is the key factor for many practical applications. The ac conductivity of this material increases with increasing frequency irrespective of the compositional variation. An anomalous behavior related to the relaxation mechanism is observed for these materials which also suggest that the materials follow the non-Debye type dielectric relaxation. The complex impedance plots (Z '' vs Z') i.e. the cole-cole plots demonstrate the contribution of grain, grain boundary and conducting nature of these nickel iron oxides. The overall dielectric property and ac conductivity infer the potential application of this nickel iron oxide in energy storage and entrenched electronics devices.