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<p>Iron oxides, particularly maghemite (γ-Fe₂O₃), are widely explored for energy storage applications due to their chemical stability and favorable dielectric behavior. However, their relatively high dielectric loss typically around 4 at low frequencies limits their efficiency in high-frequency electronic devices. To address this challenge, we investigated cobalt doping as a strategy to enhance dielectric performance. Fe₂₋ₓCoₓO₃ nanoparticles (x = 0 to 0.1) were synthesized using a sol–gel method followed by thermal treatment. The incorporation of cobalt significantly reduced dielectric loss, achieving values as low as ~ 1 for Fe₁.₉Co₀.₁O₃ representing a 75% improvement over undoped Fe₂O₃. Dielectric loss also exhibited strong frequency dependence, with substantial reductions across the 10<sup>2</sup>–10⁶ Hz range, highlighting the material’s potential for high-frequency applications. X-ray diffraction confirmed retention of the spinel structure with minor lattice expansion due to Co<sup>2</sup>⁺ substitution. SEM and TEM analyses showed uniformly dispersed nanoparticles with average sizes below 50 nm. Impedance spectroscopy revealed that cobalt doping altered charge transport dynamics, evidenced by a shift in the real part of the electrical modulus (M′) toward higher frequencies, indicating enhanced charge carrier confinement. The imaginary part (M′′) displayed relaxation peaks shifting to lower frequencies with increasing Co content, suggesting extended relaxation times caused by charge trapping at Co-induced localized states. Furthermore, Arrhenius analysis of relaxation frequencies showed increased activation energy at moderate doping levels (e.g., 0.02 Co), imposing energy barriers to charge mobility, while higher doping levels (x = 0.1) induced structural changes that modified conduction mechanisms. These results demonstrate that cobalt doping effectively tunes the dielectric and electrical properties of γ-Fe₂O₃, making it a promising candidate for high-frequency capacitive storage and resistive switching applications requiring precise control over charge transport and relaxation behavior.</p>

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Tailoring the dielectric properties of Fe2-xCoxO3 nanoparticles for high-frequency energy storage applications

  • 期刊论文

  • 发表日期：

    2025年5月31日

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  • Abdullah M. Aldukhayel

摘要

Iron oxides, particularly maghemite (γ-Fe₂O₃), are widely explored for energy storage applications due to their chemical stability and favorable dielectric behavior. However, their relatively high dielectric loss typically around 4 at low frequencies limits their efficiency in high-frequency electronic devices. To address this challenge, we investigated cobalt doping as a strategy to enhance dielectric performance. Fe₂₋ₓCoₓO₃ nanoparticles (x = 0 to 0.1) were synthesized using a sol–gel method followed by thermal treatment. The incorporation of cobalt significantly reduced dielectric loss, achieving values as low as ~ 1 for Fe₁.₉Co₀.₁O₃ representing a 75% improvement over undoped Fe₂O₃. Dielectric loss also exhibited strong frequency dependence, with substantial reductions across the 102–10⁶ Hz range, highlighting the material’s potential for high-frequency applications. X-ray diffraction confirmed retention of the spinel structure with minor lattice expansion due to Co2⁺ substitution. SEM and TEM analyses showed uniformly dispersed nanoparticles with average sizes below 50 nm. Impedance spectroscopy revealed that cobalt doping altered charge transport dynamics, evidenced by a shift in the real part of the electrical modulus (M′) toward higher frequencies, indicating enhanced charge carrier confinement. The imaginary part (M′′) displayed relaxation peaks shifting to lower frequencies with increasing Co content, suggesting extended relaxation times caused by charge trapping at Co-induced localized states. Furthermore, Arrhenius analysis of relaxation frequencies showed increased activation energy at moderate doping levels (e.g., 0.02 Co), imposing energy barriers to charge mobility, while higher doping levels (x = 0.1) induced structural changes that modified conduction mechanisms. These results demonstrate that cobalt doping effectively tunes the dielectric and electrical properties of γ-Fe₂O₃, making it a promising candidate for high-frequency capacitive storage and resistive switching applications requiring precise control over charge transport and relaxation behavior.