Calcination temperature effects on the electrical properties of Ni_0.6Cd_0.4FeAl_0.5Cu_0.5O₄

Spinel ferrites are promising materials for electronic applications due to their tunable structural and electrical properties, which can be significantly influenced by sintering temperature. In this work, Ni0.6Cd0.4FeAl0.5Cu0.5O4 ferrite was synthesized via the sol-gel method and sintered at 850 degrees C and 950 degrees C to investigate the impact of thermal treatment on its electrical and dielectric behavior. Electrical conductivity, dielectric response, and thermodynamic parameters were systematically examined through impedance spectroscopy across a wide frequency and temperature range. The results show that samples sintered at 950 degrees C exhibited enhanced electrical conductivity, reduced activation energy (0.315 eV vs. 0.358 eV at 850 degrees C), higher dielectric constants, and improved charge relaxation dynamics. Conduction was found to be governed by correlated barrier hopping (CBH) and non-overlapping small polaron tunneling (NSPT) mechanisms, with activation energies from DC conductivity and relaxation times in close agreement. Nyquist plot analysis confirmed the non-Debye relaxation behavior and highlighted the influence of both grain and grain boundary contributions. Thermodynamic analysis further revealed negative entropy changes, suggesting strong dipole-dipole interactions and reduced disorder at elevated temperatures. Overall, the results demonstrate that higher sintering temperatures improve the microstructure, conductivity, and dielectric performance, making Ni0.6Cd0.4FeAl0.5Cu0.5O4 ferrite a suitable candidate for microwave and high-frequency electronic applications.