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<p>Aluminium oxide nanoparticles (γ-Al<sub>2</sub>O<sub>3</sub> NPs) were synthesized by a straightforward chemical co-precipitation method using aluminium nitrate and sodium hydroxide, followed by calcination at 600&#xa0;°C. X-ray diffraction confirmed the formation of cubic γ-Al<sub>2</sub>O<sub>3</sub> NPs with an average crystallite size of about 6.5&#xa0;nm. Microscopic analyses (FESEM and HRTEM) revealed nearly spherical particles with sizes between 15 and 55&#xa0;nm, and EDX mapping confirmed a uniform distribution of aluminum and oxygen across the sample. UV-visible spectroscopy showed a sharp absorption edge at 260&#xa0;nm corresponding to a direct optical band gap of 5.51&#xa0;eV, while FTIR spectra displayed the characteristic Al-O vibrational modes. Dielectric measurements on γ-Al<sub>2</sub>O<sub>3</sub> NPs pellets (1–5&#xa0;mm) across the frequency range 10<sup>− 2</sup>-10<sup>5</sup> Hz and temperatures of 25–100&#xa0;°C showed that the dielectric constant, dielectric loss, and capacitance increased with temperature and thickness but decreased with frequency, consistent with Maxwell-Wagner interfacial polarization. Complex-modulus and Argand-plane analyses exhibited depressed semicircular arcs, confirming non-Debye relaxation, whereas AC conductivity increased with temperature and thickness, indicating thermally activated charge transport suggesting thermally activated hopping conduction. This study presents the first systematic correlation among thickness, temperature, and frequency on the dielectric relaxation and charge-transport behavior of γ-Al<sub>2</sub>O<sub>3</sub> NPs, revealing a tunable dielectric response that highlights their promise for high-frequency electronic and energy-storage applications.</p>

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Structural, Dielectric, AC Conductivity, and Impedance Properties of γ-Al2O3 Nanoparticles Synthesized for Electronic Applications

  • 期刊论文

  • 发表日期：

    2026年1月17日

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  • Sukdev Dewangan,
  • Shyama Prasad Mahapatra

摘要

Aluminium oxide nanoparticles (γ-Al2O3 NPs) were synthesized by a straightforward chemical co-precipitation method using aluminium nitrate and sodium hydroxide, followed by calcination at 600 °C. X-ray diffraction confirmed the formation of cubic γ-Al2O3 NPs with an average crystallite size of about 6.5 nm. Microscopic analyses (FESEM and HRTEM) revealed nearly spherical particles with sizes between 15 and 55 nm, and EDX mapping confirmed a uniform distribution of aluminum and oxygen across the sample. UV-visible spectroscopy showed a sharp absorption edge at 260 nm corresponding to a direct optical band gap of 5.51 eV, while FTIR spectra displayed the characteristic Al-O vibrational modes. Dielectric measurements on γ-Al2O3 NPs pellets (1–5 mm) across the frequency range 10− 2-105 Hz and temperatures of 25–100 °C showed that the dielectric constant, dielectric loss, and capacitance increased with temperature and thickness but decreased with frequency, consistent with Maxwell-Wagner interfacial polarization. Complex-modulus and Argand-plane analyses exhibited depressed semicircular arcs, confirming non-Debye relaxation, whereas AC conductivity increased with temperature and thickness, indicating thermally activated charge transport suggesting thermally activated hopping conduction. This study presents the first systematic correlation among thickness, temperature, and frequency on the dielectric relaxation and charge-transport behavior of γ-Al2O3 NPs, revealing a tunable dielectric response that highlights their promise for high-frequency electronic and energy-storage applications.