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<p>The relaxation behavior and charge transport mechanisms of MnO₂-doped sodium–zinc phosphate glasses were systematically investigated using impedance spectroscopy over a wide temperature and frequency range. Complex impedance, electric modulus, and dielectric analyses reveal non-Debye type relaxation behavior. The relaxation dynamics were analyzed using Davidson–Cole, Cole–Cole, Kohlrausch–Williams–Watts (KWW), and modified KWW formalisms. AC conductivity follows Jonscher’s universal power law, and the temperature dependence of the frequency exponent suggests a correlated barrier hopping (CBH) mechanism. The activation energies derived from DC conductivity and relaxation analysis indicate thermally activated hopping transport. A systematic variation of transport parameters with MnO₂ concentration suggests a gradual transition from predominantly electronic hopping to mixed ionic–electronic conduction. These findings provide deeper insight into charge transport phenomena in transition-metal-containing phosphate glass systems. The conductivity behavior was examined using the Cole–Cole and power-law models and the results were found to be mutually consistent. Bulk and interfacial/electrode polarisation responses were determined by fitting the impedance spectra with constant phase elements (CPEs) in an equivalent circuit model. Nyquist plots of impedance and electric modulus confirmed the non-Debye relaxation behavior. The temperature-dependent variation of the frequency exponent s is analyzed within the framework of hopping-type transport models, consistent with recent reports on mixed ionic–electronic conduction in related phosphate glass systems, indicating a correlated barrier hopping (CBH) mechanism for AC conductivity. Overall, the results demonstrate that the glasses exhibit temperature-dependent conductivity, showing thermally activated behavior, consistent with hopping-type transport in amorphous materials, which is dependent on the manganese content in the glass matrix.</p>

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Impedance spectroscopic analysis of relaxation and charge transport in MnO2-doped sodium–zinc phosphate glasses

  • 期刊论文

  • 发表日期：

    2026年4月9日

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  • N. Hanumantharaju,
  • V. C. Veeranna Gowda,
  • A. Jayasheelan,
  • G. Sriprakash

摘要

The relaxation behavior and charge transport mechanisms of MnO₂-doped sodium–zinc phosphate glasses were systematically investigated using impedance spectroscopy over a wide temperature and frequency range. Complex impedance, electric modulus, and dielectric analyses reveal non-Debye type relaxation behavior. The relaxation dynamics were analyzed using Davidson–Cole, Cole–Cole, Kohlrausch–Williams–Watts (KWW), and modified KWW formalisms. AC conductivity follows Jonscher’s universal power law, and the temperature dependence of the frequency exponent suggests a correlated barrier hopping (CBH) mechanism. The activation energies derived from DC conductivity and relaxation analysis indicate thermally activated hopping transport. A systematic variation of transport parameters with MnO₂ concentration suggests a gradual transition from predominantly electronic hopping to mixed ionic–electronic conduction. These findings provide deeper insight into charge transport phenomena in transition-metal-containing phosphate glass systems. The conductivity behavior was examined using the Cole–Cole and power-law models and the results were found to be mutually consistent. Bulk and interfacial/electrode polarisation responses were determined by fitting the impedance spectra with constant phase elements (CPEs) in an equivalent circuit model. Nyquist plots of impedance and electric modulus confirmed the non-Debye relaxation behavior. The temperature-dependent variation of the frequency exponent s is analyzed within the framework of hopping-type transport models, consistent with recent reports on mixed ionic–electronic conduction in related phosphate glass systems, indicating a correlated barrier hopping (CBH) mechanism for AC conductivity. Overall, the results demonstrate that the glasses exhibit temperature-dependent conductivity, showing thermally activated behavior, consistent with hopping-type transport in amorphous materials, which is dependent on the manganese content in the glass matrix.