Microwave-Assisted Green Combustion Synthesis of Phase-Pure MgFe2O4 Nanoparticles using Tinospora cordifolia: Structural Characterization and Electrical Relaxation Behaviour

Abstract

Phase-pure MgFe₂O₄ nanoparticles were successfully synthesized via a rapid microwave-assisted green combustion route using Tinospora cordifolia (giloy) extract as a natural phytochemical combustion fuel without post-combustion calcination of the synthesized powder. The crystal structure and microstructure of the synthesized nanoparticles and the electrical properties of sintered pellets prepared from the synthesized powder were systematically investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and temperature-dependent dielectric measurements. XRD confirmed the formation of a single-phase cubic spinel structure (space group Fd3̅m) without detectable secondary phases. The average crystallite sizes estimated by the Debye–Scherrer, Williamson–Hall (UDM) and size–strain plot (SSP) methods were 15.10, 18.36 and 18.26 nm, respectively. The close agreement among these values confirms the nanocrystalline nature of MgFe₂O₄, with relatively low lattice strain. FTIR spectra exhibited the characteristic tetrahedral and octahedral metal-oxygen vibrational bands of the spinel lattice, while SEM and EDS analyses revealed a porous agglomerated morphology and confirmed the presence of Mg, Fe and O. Dielectric measurements performed over the frequency range of 1 Hz-100 kHz and the temperature range from room temperature to 400 ºC showed pronounced temperature- and frequency-dependent dielectric behaviour consistent with Maxwell-Wagner interfacial polarization and thermally activated electron hopping processes. The AC conductivity exhibited thermally activated semiconducting behaviour, whereas electric modulus analysis revealed broad relaxation features characteristic of non-Debye dielectric relaxation. The relaxation times derived from the consistently selected high-temperature M" relaxation features followed an approximately Arrhenius-type dependence, with an activation energy of 0.758 eV.