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<p>In the present work, the mixed alkali effect (MAE) in a Na₂O–Li₂O–ZnO–PbCl₂ glassy system based on Na–Li combinations was investigated using powder X-ray diffraction (PXRD), density and molar volume measurements, complex impedance analysis, DC and AC conductivity, and dielectric relaxation studies. The average crystallite size exhibits a minimum at a relative composition of 0.85, while the density shows a minimum at a relative composition of 0.5. These observations indicate that both crystallite size and density clearly demonstrate the presence of the MAE. The ionic DC conductivity and hopping conductivity also show a pronounced MAE, decreasing by more than four orders of magnitude at 513&#xa0;K for the Na–Li alkali pair in the present system. This behavior suggests that the MAE can be interpreted as a natural consequence of random ion mixing, wherein ion transport is favored between energetically well-matched sites. Consequently, the MAE arises due to structural mismatch between neighboring sites occupied by dissimilar ions. Furthermore, dielectric coupling between the slower Na⁺ ions and the faster Li⁺ ions may contribute to the MAE in the present system, leading to phenomena such as volume relaxation and the wave-shaped nature of viscosity. The primary objective of this study is to elucidate the fundamental mechanisms underlying the MAE in mixed alkali glass-ceramics, correlating structural, electrical, and dielectric properties with ionic transport phenomena. From an application perspective, understanding and controlling the MAE in these materials can enable tailoring of ionic conductivity and dielectric behavior, making the system promising for battery electrolytes, energy storage devices, dielectric components, and optical applications.</p>

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Mixed alkali effect in Na2O-Li2O glass-ceramics: studies of physical properties and transport phenomena

  • 期刊论文

  • 发表日期：

    2026年4月29日

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  • Rakesh Ram,
  • Sanjib Bhattacharya

摘要

In the present work, the mixed alkali effect (MAE) in a Na₂O–Li₂O–ZnO–PbCl₂ glassy system based on Na–Li combinations was investigated using powder X-ray diffraction (PXRD), density and molar volume measurements, complex impedance analysis, DC and AC conductivity, and dielectric relaxation studies. The average crystallite size exhibits a minimum at a relative composition of 0.85, while the density shows a minimum at a relative composition of 0.5. These observations indicate that both crystallite size and density clearly demonstrate the presence of the MAE. The ionic DC conductivity and hopping conductivity also show a pronounced MAE, decreasing by more than four orders of magnitude at 513 K for the Na–Li alkali pair in the present system. This behavior suggests that the MAE can be interpreted as a natural consequence of random ion mixing, wherein ion transport is favored between energetically well-matched sites. Consequently, the MAE arises due to structural mismatch between neighboring sites occupied by dissimilar ions. Furthermore, dielectric coupling between the slower Na⁺ ions and the faster Li⁺ ions may contribute to the MAE in the present system, leading to phenomena such as volume relaxation and the wave-shaped nature of viscosity. The primary objective of this study is to elucidate the fundamental mechanisms underlying the MAE in mixed alkali glass-ceramics, correlating structural, electrical, and dielectric properties with ionic transport phenomena. From an application perspective, understanding and controlling the MAE in these materials can enable tailoring of ionic conductivity and dielectric behavior, making the system promising for battery electrolytes, energy storage devices, dielectric components, and optical applications.