Thermal annealing temperature evolution of structural and dielectric properties of MgFe 2 O 4

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Abstract Evolution of structural and dielectric characteristics as a function of thermal annealing temperature (400–600 °C/2h) of MgFe 2 O 4 ferrite nano-powder prepared by sol-gelsynthesis-protocol is reported. Structural characterization is done by X-ray diffraction (XRD), and dielectric response was recorded. XRD confirms presence of nano-crystalline spinel-phase bearing grain diameters in range of 48.01 nm – 64.59 nm. Evolution of structural properties with thermal annealing reveals: i) minor decrease of lattice parameter, ii) Grain growth (from 48.01 – 64.59 nm), iii) weakened A–B, A–A super-exchange and simultaneous increment in the strength of B–B super-exchange interaction, showing decrease of Néel magnetic moment, iv) changes in oxygen parameter and degree of inversion owing to increasing population of Mg 2+ at A site, and that of Fe 3+ ions at B site, v) as frequency increases, real (ε'), imaginary (ε") parts of dielectric-constant, and loss (tan δ) shows declination, vi) AC conductivity (σ ac ) exhibited a power-law dependence and showed a notable increase at higher frequencies. Complex impedance analysis indicates that grain-boundaries significantly influence the dielectric performance at higher frequencies. Enhanced behaviour of σ ac , suggests prospective use of pure MgFe 2 O 4 in RF-based dielectric and electronic device applications.

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