Lead-free ferroelectric ceramics have attracted significant attention as sustainable alternatives to Pb-based materials due to their environmental compatibility and multifunctional properties. In this study, the presence of Er and Fe in BNT-based ceramics , (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25) were synthesized using the conventional solid-state reaction method and characterized through a combination of structural, optical, microstructural, dielectric, and magnetic analyses. X-ray diffraction confirmed the formation of a single-phase rhombohedral perovskite structure. Microstructural analysis using FESEM and AFM revealed an increase in grain size from 297.71 to 5.08 μm and decrease in the roughness, which contributed to improved dielectric performance. A clear decreasing trend in the band gap 2.811 eV to 1.509 eV with increasing doping concentration (x = 0.05 to 0.25) was observed, highlighting the material’s application for optoelectronic devices. Dielectric studies indicated appropriate permittivity with low dielectric loss across a wide frequency range, making the material suitable for energy storage and capacitor applications. Furthermore, magnetic hysteresis (M-H) measurements demonstrated the antiferromagnetic nature with weak ferromagnetism. Er3+ ions with unique f-electron transitions impart to optical behavior and Fe3+ ions with magnetic moments contribute to magnetic properties of the doped BNT material. This multifunctional behavior is not typically seen in undoped BNT. Hence, this material poses applications for magneto-dielectric sensors, spintronics, opto-electronic devices

The ferrite samples Mg0.5Mn0.5Fe2-xErxO4 (x = 0, 0.02, 0.04, 0.06, 0.1) prepared using the solid-state route were evaluated for microwave absorption applications. X-ray diffraction with Rietveld refinement revealed multiphase characteristics and the coexistence of a spinel phase with an orthorhombic phase attributed to the larger Er3+ ionic radius. The SEM analysis of rare earth-doped spinel ferrites reveals that grain size and porosity are significantly influenced by doping concentration, which in turn strongly affect the dielectric and magnetic properties. AFM indicated high surface roughness. The favourable figures of dielectric constant and loss factor recorded at frequency variation makes the material suitable in high frequency performances. The Er modified ferrites possessing a broad range of relaxation period can interact and effectively absorb an extended range of spectrum from the microwave frequency range. UV–Vis spectroscopy demonstrated an increase in the optical forbidden band gap from 1.06 eV to 2.30 eV after doping of erbium, enhancing light absorption. The combined improvements in optical, dielectric, and thermal properties confirm that Er-modified ferrites are promising candidates for high-frequency, high-temperature microwave absorbing applications. The increase of coercivity with respect to doping concentration may be attributed to the anisotropy due to the strong spin orbit coupling of Er3+.

Erbium doped MgNiFe2O4 with composition MgNiFe2-xErxO4 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) have been prepared by ceramic processing technique. The existence of spinel cubic phase and secondary phase of ErFeO3 orthorhombic structure have been confirmed in the Er-doped MgNiFe2O4 from the Rietveld analysis of XRD pattern. The Williamson-Hall graph shows the decrease of average crystallite size of spinel phase due to compressive strain after Er-doping. UV spectra analysis shows an increasing trend of band gap after incorporating Er3+. The dielectric constant shows decreasing trend and dielectric loss shows increasing trend with respect to frequency for all the ferrites. The nature of the M − H loops for all the specimens show a soft ferromagnetic behavior. The synthesized samples have modified electrical and magnetic behaviors suitable for microwave applications.