Effect of annealing temperature on the structural, dielectric and electric properties of $\hbox {Ni}_{{0.7}} \hbox {Cd}_{0.3}\hbox {Fe}_{2}\hbox {O}_{4}$ ferrites

Abstract

A composition of Ni$_{{0.7}}\hbox {Cd}_{{0.3}}\hbox {Fe}_{{2}}\hbox {O}_{{4}}$ (NCF) ferrite nanoparticles was synthesized by a sol–gel auto-combustion technique. The particles in powder form were annealed at 550 and 700$^{\circ }\hbox {C}$ to study the structural, dielectric and electric properties of NCF by using X-ray diffraction (XRD), field emission scanning electron microscopy, impedance and modulus spectroscopy. XRD patterns confirmed the single phase cubic spinel structure of the sample. The average crystallite size of NCF was found to be 17 nm at 550$^{\circ }\hbox {C}$ and 31 nm at 700$^{\circ }\hbox {C}$, respectively. The variation in complex dielectric constant, loss tangent and impedance along with the modulus properties of NCF with frequencies was observed at room temperature because of their size and annealing temperature. Notably, dielectric dispersion of the materials was observed at low frequencies because of Maxwell–Wagner interfacial polarization. The impedance and modulus spectroscopy were used to investigate the electric properties of the materials, which revealed the increase in grain and grain boundary resistance with annealing temperature. A non-Debye type of relaxation in the materials was evidenced through the Cole–Cole study of impedance and modulus spectra.