Characterization and frequency-thermal response of electrical properties of Cu nanoferrite prepared by sol–gel method

• Results are compatible with the Maxwell–Wagner model and the phenomenological Koop's theory.
• Measured loss tangent and conductivities were low, but increased with temperature.
• Conductivity of Cu ferrites followed the localized hopping mechanism and Jonscher's law.
• The electrical modulus shows relaxation of interfacial polarization, relaxation time increases with temperature.
• Using impedance analysis with Cole–Cole equation, the effect of resistance of grains is shown.

In this paper, we have synthesized copper ferrite nanocrystals using sol–gel method. X-ray diffraction (XRD) analysis confirms that the ferrite has cubic spinal structure and shows Jahn–Teller effect. Also, scan electron microscope (SEM) image demonstrates that grains are nano size order. We showed that the dielectric properties are compatible with the Maxwell–Wagner model and phenomenological Koop's theory. Loss tangent and conductivity of the ferrite have been measured to have small values of 2.4 and 2×10−7 S/m, respectively at room temperature and at 12 Hz. Conductivity has been investigated in terms of localized hopping mechanism and good obedience of Jonscher's law was observed. Variation of activation energy was studied and showed a transition temperature of 443 °K. The electrical modulus shows relaxation of interfacial polarization with relaxation time of 0.318 ms at 24 °C and 15.9 μs at 72 °C. In Impedance spectroscopy, we observed the effects of grain and grain boundary. By increasing temperature, capacity and conduction would increase which show easier polarization process and a semiconducting behavior. Also, relaxation times are shifted to smaller values to represent increasing the electrons mobility.