Effect of lithium doping on frequency-dependent dielectric properties of manganese ferrite nanoparticles

Abstract

For enhancing the charge storage of nanoparticles by modifying the grains, a novel lithium-doped iron-based nanoparticle (Li_2xMn_1–xFe₂O₄) was designed and synthesized. Lithium-doped manganese ferrite (Li_2xMn_1–xFe₂O₄) nanoparticles were prepared using sol–gel route with different doping concentrations of lithium, i.e., x = 0, 0.25, 0.50, 0.75, and 1.0 when annealed at 500 °C temperature. The structure (crystal structure and crystallite size), vibrational modes (functional groups of molecules), morphology, and composition were investigated and confirmed by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The vibrational bands shifted towards high wavenumbers due to small ionic radii of Li⁺¹ to Mn⁺² which indicated the successful replacement of lithium with manganese in Li_2xMn_1–xFe₂O₄ nanoparticles and redistribution of cations between octahedral and tetrahedral sites. Moreover, the dielectric parameters of Li_2xMn_1–xFe₂O₄ nanoparticles were investigated using LCR at room temperature. The dielectric parameters revealed improved dielectric properties ($\varepsilon_{r}^{^{\prime}}$ 168, $\varepsilon_{r}^{^{\prime\prime}}$ 332, tanδ 2.63, and σ_ac 3.78 × 10^–4 Ω⁻¹ m⁻¹) with increasing concentrations of lithium in Li_2xMn_1–xFe₂O₄ nanoparticles owed to increasing Fe²⁺ ions at the octahedral sites. Furthermore, these Li_2xMn_1–xFe₂O₄ nanoparticles offered large places and provoke more active sites for storage due to their high ac-conductivity. Henceforth, it can be suggested that lithium-doped manganese ferrite nanoparticles can be the best candidate for energy storage devices.