Spectral, electrical, and dielectric characterization of Ce-doped Co-Mg-Cd spinel nano-ferrites synthesized by the sol-gel auto combustion method

Abstract

The spinel nano-ferrites with composition Co0.5Mg0.25Cd0.25Fe2-xCexO4 (0.0 ≤ x ≤ 0.2 with a step interval of 0.05) synthesized by sol-gel auto combustion method. Samples sintered at a significant temperature of 800 °C for 8 h. XRD confirmed the formation of spinel matrix and reduction in lattice constant from 8.3941 Å to 8.3598 Å by increasing Ce3+ cations. The crystalline size of prepared nano-ferrites reduced from 33.6 nm to 14.5 nm. Two absorption bands in the range of 405.23–435.12 cm−1 for octahedral and 510.85–523.21 cm−1 for the tetrahedral site were detected by using FTIR. The UV–visible study showed the optical band gaps decreased from 3.01 eV to 2.25 eV with decreasing Ce3+ doping. The electrical resistivity of as-prepared nano-ferrites increased in the Ferro region and decreased in the Para region with increasing temperature. The resistivity decreased with Ce3+ doping increase, and drift mobility has an opposite trend of resistivity. Due to the effect of space-charge polarization, the values of the dielectric constant (ε′) and dielectric constant loss (ε″) and tan δ were reduced as the frequency was increased, and displayed a dispersive behavior at higher frequencies.