Dielectric, impedance and electric modulus properties of lanthanum-doped zinc spinel ferrite (ZnLa_xFe_2−xO₄) nanomaterials

In this study, lanthanum-doped zinc spinel ferrite (ZnLa_xFe_2−xO₄) nanoparticles (NPs) were synthesized using the sol–gel technique with varying doping concentrations (x = 0.00, 0.05, 0.10, 0.15 and 0.20). Each sample was annealed at 600 °C for 3 h to achieve the crystalline phase of the NPs. X-ray diffraction (XRD) analysis confirmed a cubic lattice structure with the Fd3m space group. The crystallite size was determined using the Scherrer equation associated with the modified Scherrer and Williamson–Hall approaches as well as the size–strain plot technique. Fourier-transform infrared spectroscopy was employed to investigate the chemical composition of the NPs, revealing two distinct absorption peaks at 420 and 530 cm⁻¹. Transmission electron microscopy results on the internal morphology were consistent with the XRD results. The dielectric properties of the NPs were investigated using an LCR meter over a frequency lies between 1 MHz and 3 M Hz under room temperature condition. For all samples, Cole–Cole plots were analyzed to describe the conduction phenomenon. The hysteresis loops confirmed that the undoped zinc ferrite NPs exhibit ferromagnetic behavior. The incorporation of multi-walled carbon nanotubes led to a reduction in magnetic parameters, such as saturation magnetization (M_s), coercivity (H_c), remanent magnetization (M_r), squareness ratio (M_r/M_s) and anisotropy constant (K). These results demonstrate that zinc spinel ferrites possess great potential for energy storage and microwave applications.