Eu-doped Mg–Ni ferrites: a reliable strategy to enhance dielectric properties for high-frequency applications

In this study, we synthesized Mg_0.5Ni_0.5Fe₂O₄ (MNFO) spinel ferrites and Eu-doped spinel Mg_0.5Ni_0.5Fe_1.98Eu_0.02O₄ (MNFEuO) using a solid-state method. Our comprehensive analysis included structural, morphological, and dielectric properties. X-ray diffraction confirmed the cubic structure of both MNFO and MNFEuO. The Rietveld refinement revealed an increased lattice constant for the Eu-doped sample, attributed to the larger ionic radius of Eu³⁺ ions. The crystallite size was 46 nm for MNFO and 80 nm for MNFEuO. The bulk densities were measured as 4.32 g/cm³ for MNFO and 4.41 g/cm³ for MNFEuO, with the theoretical densities calculated as 4.96 g/cm³ and 4.98 g/cm³, respectively. Scanning electron microscopy (SEM) indicated well-defined, spherical particles with uniform size distribution and average grain sizes of 0.86 µm for MNFO and 0.62 µm for MNFEuO. X-ray photoelectron spectroscopy (XPS) confirmed the purity and oxidation states of the elements. Impedance spectroscopy showed a significant enhancement in conductivity for MNFEuO, with DC conductivity values at 600 K of 57 × 10⁻⁴ S m⁻¹ for MNFO and 107.4 × 10⁻⁴ S m⁻¹ for MNFEuO, indicating superior electrical performance in the doped sample. Dielectric analysis demonstrated an increase in the dielectric constant for MNFEuO compared to MNFO, suggesting improved polarization properties. These findings indicate that Eu-doped spinel ferrites possess promising potential for high-frequency and advanced electronic applications.