Structural, vibrational, and dielectric characterization of sol–gel synthesized spinel ferrite for high-performance multifunctional applications

Ni₀.₄Cd₀.₃Mg₀.₃Fe₂O₄ spinel ferrite was synthesized by the sol–gel method and calcined at 950 °C. XRD confirmed a well-crystallized cubic spinel structure with crystallite sizes between 99 and 113 nm. Dielectric and conductivity analyses revealed that conduction and relaxation are driven by the same charge carriers, with increased charge carrier mobility at higher frequencies. The Non-Small Polaron Tunneling (NSPT) model successfully described charge transport—selected over alternatives like CBH or OLPT due to the observed increase in the frequency exponent s with temperature—yielding a low activation energy (0.025 eV) and a polaron binding energy of 0.41 eV. Ghosh scaling demonstrated universal transport behavior, while impedance spectroscopy highlighted the role of grains and grain boundaries. The material’s high resistivity at room temperature makes it a promising candidate for microwave and electronic device applications.