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<p>Using a novel chemical precipitation method, the researchers synthesized pure CdO and CdO/CeO<sub>2</sub> composites.&#xa0;They thoroughly analyzed these materials for their structure, shape, thermal, and dielectric properties. X-ray diffraction (XRD) tests unequivocally confirmed the successful synthesis of CdO and CeO₂ phases. In the CdO/CeO₂ phase, a peak shift occurred toward lower 2<i>θ</i> values. The increase in lattice strain and dislocation density led to a reduction in crystallite size, decreasing from 28.28&#xa0;nm (CdO) to 20.15&#xa0;nm (CdO/CeO₂). This indicates more structural disorder from the inclusion of CeO<sub>2</sub> due to ionic mismatch. UV–Vis spectroscopy revealed an increase in the direct bandgap from 4.59 to 5.83&#xa0;eV, attributed to defect-induced band tailing and Ce<sup>4+</sup> -induced hybridization mechanisms. Field emission scanning electron microscopy (FE-SEM) revealed a decrease in the average grain size from 45–60&#xa0;nm (CdO) to 30–50&#xa0;nm (CdO/CeO<sub>2</sub>) and a simultaneous increase in porosity from 1.57% to 6.17%. These changes led to increased interfacial polarization. The dielectric constant (<i>ε</i>′) in CdO/CeO₂ exhibited a notable increase with temperature, peaking at 107.62 at 200&#xa0;°C. In contrast, the&#xa0;dielectric constant&#xa0;for pure CdO decreased&#xa0;as&#xa0;the temperature&#xa0;rose. The dielectric loss (<i>ε</i>″) and loss tangent (tan δ) were notably lower in the composite, indicating better energy efficiency. AC conductivity (<i>σ</i><sub>ac</sub>) followed Jonscher’s power law, showing a frequency-dependent increase and better retention in the CdO/CeO₂ nanocomposite. Impedance spectroscopy revealed that the activation energy (<i>E</i>ₐ) for CdO/CeO₂ was lower (0.48&#xa0;eV at 200&#xa0;°C) compared to CdO (0.52&#xa0;eV), supporting thermally activated hopping conduction mechanisms. Modulus spectroscopy (<i>M</i>′, <i>M</i>″) showed non-Debye relaxation behavior, with relaxation peaks shifting toward higher frequencies, consistent with Maxwell–Wagner and Koop’s models. At higher frequencies (log f ≈ 5–6), both materials demonstrated a decrease in shielding effectiveness (SE). CdO/CeO₂ had negative values around –10&#xa0;dB, which resulted from weak absorption, reduced reflection, or possible measurement errors. This suggests a shift from reflection-dominated to absorption-limited&#xa0;electromagnetic interference (EMI) shielding&#xa0;behavior. Although pure CdO exhibited stronger EMI shielding due to higher dielectric losses, the CdO/CeO₂ nanocomposite offers superior electrical conductivity, reduced energy dissipation, and enhanced dielectric stability. These characteristics position the CdO/CeO₂ nanocomposite as a promising option for advanced applications in high-frequency electronics, energy storage systems, and EMI shielding.</p>

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Enhanced dielectric stability and electromagnetic shielding efficiency of CdO/CeO₂ nanocomposites for high-performance electronic applications

  • 期刊论文

  • 发表日期：

    2025年7月21日

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  • V. Charles Vincent,
  • P. Elaiyaraja,
  • S. Senthil,
  • A. Antony Prabhu,
  • V. Ratchagar,
  • G. Saravanan,
  • T. Senthil Ganesh,
  • S. Srinivasan

摘要

Using a novel chemical precipitation method, the researchers synthesized pure CdO and CdO/CeO2 composites. They thoroughly analyzed these materials for their structure, shape, thermal, and dielectric properties. X-ray diffraction (XRD) tests unequivocally confirmed the successful synthesis of CdO and CeO₂ phases. In the CdO/CeO₂ phase, a peak shift occurred toward lower 2θ values. The increase in lattice strain and dislocation density led to a reduction in crystallite size, decreasing from 28.28 nm (CdO) to 20.15 nm (CdO/CeO₂). This indicates more structural disorder from the inclusion of CeO2 due to ionic mismatch. UV–Vis spectroscopy revealed an increase in the direct bandgap from 4.59 to 5.83 eV, attributed to defect-induced band tailing and Ce4+ -induced hybridization mechanisms. Field emission scanning electron microscopy (FE-SEM) revealed a decrease in the average grain size from 45–60 nm (CdO) to 30–50 nm (CdO/CeO2) and a simultaneous increase in porosity from 1.57% to 6.17%. These changes led to increased interfacial polarization. The dielectric constant (ε′) in CdO/CeO₂ exhibited a notable increase with temperature, peaking at 107.62 at 200 °C. In contrast, the dielectric constant for pure CdO decreased as the temperature rose. The dielectric loss (ε″) and loss tangent (tan δ) were notably lower in the composite, indicating better energy efficiency. AC conductivity (σac) followed Jonscher’s power law, showing a frequency-dependent increase and better retention in the CdO/CeO₂ nanocomposite. Impedance spectroscopy revealed that the activation energy (Eₐ) for CdO/CeO₂ was lower (0.48 eV at 200 °C) compared to CdO (0.52 eV), supporting thermally activated hopping conduction mechanisms. Modulus spectroscopy (M′, M″) showed non-Debye relaxation behavior, with relaxation peaks shifting toward higher frequencies, consistent with Maxwell–Wagner and Koop’s models. At higher frequencies (log f ≈ 5–6), both materials demonstrated a decrease in shielding effectiveness (SE). CdO/CeO₂ had negative values around –10 dB, which resulted from weak absorption, reduced reflection, or possible measurement errors. This suggests a shift from reflection-dominated to absorption-limited electromagnetic interference (EMI) shielding behavior. Although pure CdO exhibited stronger EMI shielding due to higher dielectric losses, the CdO/CeO₂ nanocomposite offers superior electrical conductivity, reduced energy dissipation, and enhanced dielectric stability. These characteristics position the CdO/CeO₂ nanocomposite as a promising option for advanced applications in high-frequency electronics, energy storage systems, and EMI shielding.