This study investigates the influence of magnesium substitution on the structural and electrical properties of polycrystalline MgxCu1−xFe2O4 ferrites (0.0 ≤ x ≤ 1.0), synthesized via the sol-gel autocombustion method using citric acid as fuel. The aim is to evaluate how compositional variation affects dielectric behavior and conduction mechanisms. X-ray diffraction confirmed the formation of a single-phase cubic spinel across all compositions, with lattice constant variations linked to the similar ionic radii of Cu2+ and Mg2+. Crystallite size, estimated by the Williamson-Hall method, decreased with magnesium content, indicating lattice strain and cation redistribution. Transmission electron microscopy (TEM) measurements confirmed these results, showing particle sizes in the range of 23–28 nm across all compositions. Nitrogen adsorption BET analysis revealed a substantial increase in specific surface area with increasing magnesium content, reaching up to 33.05 m2/g for x = 0.8. This enhancement in surface area and mesoporosity reflects the formation of finer particles and more pronounced interfacial regions, contributing to grain boundary effects and polarization heterogeneities that influence dielectric performance. Dielectric spectroscopy revealed low-frequency dispersion and non-Debye relaxation behavior, attributed to Maxwell-Wagner polarization and Fe3+/Fe2+ hopping. The dielectric loss tangent showed a composition-dependent peak, especially at x = 1.0, suggesting the presence of relaxation dipoles. Impedance spectroscopy demonstrated that electrical response stems from both grains and grain boundaries. Havriliak-Negami model fitting supported this behavior, with α and β parameters reflecting increased disorder and broader relaxation time distributions at higher Mg contents. Activation energy analysis via Arrhenius plots showed that the energy barrier increased from 0.96 eV (x = 0.0) to over 2.0 eV (x = 1.0), indicating a shift from polaron hopping to narrow-band and defect-assisted conduction. These results confirm that magnesium substitution significantly alters dielectric response and conductivity in MgxCu1−xFe2O4 ferrites. The findings highlight the key role of cation redistribution, structural disorder, and defect dynamics in tailoring electrical properties for advanced dielectric applications.

Optimizing the structural, morphological, and dielectric properties of copper ferrite through magnesium substitution

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发表日期：

2025年8月27日

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J. Mazurenko,
A. K. Sijo,
L. Kaykan,
Ł. Gondek,
J. M. Michalik,
L. Matzui,
L. Vovchenko,
O. Yakovenko

摘要

This study investigates the influence of magnesium substitution on the structural and electrical properties of polycrystalline Mg_xCu_1−xFe₂O₄ ferrites (0.0 ≤ x ≤ 1.0), synthesized via the sol-gel autocombustion method using citric acid as fuel. The aim is to evaluate how compositional variation affects dielectric behavior and conduction mechanisms. X-ray diffraction confirmed the formation of a single-phase cubic spinel across all compositions, with lattice constant variations linked to the similar ionic radii of Cu²⁺ and Mg²⁺. Crystallite size, estimated by the Williamson-Hall method, decreased with magnesium content, indicating lattice strain and cation redistribution. Transmission electron microscopy (TEM) measurements confirmed these results, showing particle sizes in the range of 23–28 nm across all compositions. Nitrogen adsorption BET analysis revealed a substantial increase in specific surface area with increasing magnesium content, reaching up to 33.05 m²/g for x = 0.8. This enhancement in surface area and mesoporosity reflects the formation of finer particles and more pronounced interfacial regions, contributing to grain boundary effects and polarization heterogeneities that influence dielectric performance. Dielectric spectroscopy revealed low-frequency dispersion and non-Debye relaxation behavior, attributed to Maxwell-Wagner polarization and Fe³⁺/Fe²⁺ hopping. The dielectric loss tangent showed a composition-dependent peak, especially at x = 1.0, suggesting the presence of relaxation dipoles. Impedance spectroscopy demonstrated that electrical response stems from both grains and grain boundaries. Havriliak-Negami model fitting supported this behavior, with α and β parameters reflecting increased disorder and broader relaxation time distributions at higher Mg contents. Activation energy analysis via Arrhenius plots showed that the energy barrier increased from 0.96 eV (x = 0.0) to over 2.0 eV (x = 1.0), indicating a shift from polaron hopping to narrow-band and defect-assisted conduction. These results confirm that magnesium substitution significantly alters dielectric response and conductivity in Mg_xCu_1−xFe₂O₄ ferrites. The findings highlight the key role of cation redistribution, structural disorder, and defect dynamics in tailoring electrical properties for advanced dielectric applications.