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<p>This study investigates the structural properties and humidity-dependent dielectric performance of Cerium-doped Zinc Cobaltite ZnCo<sub>2-x</sub>Ce<sub>x</sub>O<sub>4</sub> (<i>x</i> = 0, 0.2, 0.5, 1.0). X-ray photoelectron spectroscopy (XPS) confirmed Zn<sup>2+</sup>, mixed Co<sup>2+</sup>/Co<sup>3+</sup>, and integrated Ce<sup>3+</sup>/Ce<sup>4+</sup> states. Surface morphology transformed from particles to flaky structures with cerium addition, increasing surface area and porosity. Raman spectroscopy revealed spinel characteristic peaks, and higher cerium levels led to significant lattice distortion. HRTEM of the undoped sample showed a nearly ordered structure with distributed nanoparticles, while the Cerium-doped samples showed a more complex and less ordered structure. SAED confirmed the polycrystalline nature in all samples. Ce-doping increased the BET surface area from 25.9 to 102.6 m<sup>2</sup>/g, creating refined mesoporosity that enhances water adsorption. Dielectric properties showed strong humidity dependence. Both permittivity (ε′) and loss (ε″) increased with RH and Ce content, decreasing with frequency in two stages. The real impedance (Zre) dropped sharply at low frequency and then fell steadily, while the imaginary impedance (Z<sub>im</sub>) shifted from a single peak in the undoped sample to multiple peaks in the doped samples. The ε′ ratio (RH 97%/11%) at 1 kHz increased from 4.11 (undoped) to 73.4 (ZC-Ce1). Humidity sensitivity (Δε′/ΔRH) improved dramatically from 1.1 (undoped) to 52.5 (ZC-Ce1), indicating a strong Ce-dependent enhancement in moisture responsiveness. The flaky, porous morphology in doped samples enhanced interfacial polarization and dispersion. These results indicate strong potential for sustainable humidity sensing applications in environmental monitoring, with additional promise for catalyst support and energy storage in supercapacitors.</p>

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Humidity modulated dielectric properties of morphology controlled Ce-doped ZnCo2O4

  • 期刊论文

  • 发表日期：

    2026年3月13日

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  • Abdelfattah Darwish,
  • Mohamed I. Farouk,
  • Amir Elzwawy,
  • Mohamed Morsy

摘要

This study investigates the structural properties and humidity-dependent dielectric performance of Cerium-doped Zinc Cobaltite ZnCo2-xCexO4 (x = 0, 0.2, 0.5, 1.0). X-ray photoelectron spectroscopy (XPS) confirmed Zn2+, mixed Co2+/Co3+, and integrated Ce3+/Ce4+ states. Surface morphology transformed from particles to flaky structures with cerium addition, increasing surface area and porosity. Raman spectroscopy revealed spinel characteristic peaks, and higher cerium levels led to significant lattice distortion. HRTEM of the undoped sample showed a nearly ordered structure with distributed nanoparticles, while the Cerium-doped samples showed a more complex and less ordered structure. SAED confirmed the polycrystalline nature in all samples. Ce-doping increased the BET surface area from 25.9 to 102.6 m2/g, creating refined mesoporosity that enhances water adsorption. Dielectric properties showed strong humidity dependence. Both permittivity (ε′) and loss (ε″) increased with RH and Ce content, decreasing with frequency in two stages. The real impedance (Zre) dropped sharply at low frequency and then fell steadily, while the imaginary impedance (Zim) shifted from a single peak in the undoped sample to multiple peaks in the doped samples. The ε′ ratio (RH 97%/11%) at 1 kHz increased from 4.11 (undoped) to 73.4 (ZC-Ce1). Humidity sensitivity (Δε′/ΔRH) improved dramatically from 1.1 (undoped) to 52.5 (ZC-Ce1), indicating a strong Ce-dependent enhancement in moisture responsiveness. The flaky, porous morphology in doped samples enhanced interfacial polarization and dispersion. These results indicate strong potential for sustainable humidity sensing applications in environmental monitoring, with additional promise for catalyst support and energy storage in supercapacitors.