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<p>ZnMo<sub>x</sub>Al<sub>2−2x</sub>O<sub>4</sub> (x = 0.00–0.10) nanospinel oxides (NSOs) were synthesized via the sol–gel route. XRD confirmed the formation of a pure cubic spinel structure with crystallite sizes ranging from <b>8.4 to 11&#xa0;nm</b>, while TEM, HR-TEM, SEM, and EDX analyses validated the cubic morphology and homogeneous chemical composition. The dielectric and electrical properties of Mo→ZnAl<sub>2</sub>O<sub>4</sub> NSOs were systematically investigated across a wide frequency range (<b>100&#xa0;Hz–1 MHz</b>) and temperature window (<b>20–120&#xa0;°C</b>). AC conductivity followed Jonscher’s universal power law, confirming a correlated barrier hopping (CBH) mechanism, where electron transport occurs via hopping between localized states. Mo doping significantly enhanced conductivity, with nearly an <b>order of magnitude improvement</b> up to the optimal doping level of <b>x = 0.06</b>, attributed to oxygen vacancies and defect dipoles that facilitate polaron hopping between Mo<sup>6+</sup>/Mo<sup>5+</sup> and Zn<sup>2+</sup>/Zn<sup>3+</sup> sites. The activation energy (Ea) increased with doping, peaking at <b>~ 0.0686&#xa0;eV for x = 0.06</b>, and subsequently decreased at higher doping levels, suggesting a transition from optimized defect-assisted conduction to defect saturation. The dielectric constant rose from <b>x = 0.00</b> to <b>x = 0.06</b> at 120&#xa0;°C, accompanied by moderate dielectric loss, reflecting enhanced dipolar relaxation and thermally activated charge carrier hopping. Impedance spectroscopy revealed depressed semicircular arcs and Warburg tails, confirming non-ideal Debye relaxation, grain boundary effects, and diffusion-limited transport. These findings demonstrate that controlled Mo substitution in ZnAl<sub>2</sub>O<sub>4</sub> nanospinel oxides can effectively tailor conduction and dielectric properties, making them promising candidates for dielectric and energy storage applications.</p>

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A temperature/frequency dependent complex impedance study, electrical transport and dielectric relaxation mechanism in mo substituted ZnAl2O4 nanospinel oxides

  • 期刊论文

  • 发表日期：

    2025年12月5日

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  • M. A. Almessiere,
  • A. V. Fulari,
  • A. Baykal,
  • Sagar E. Shirsath,
  • Md Amir

摘要

ZnMoxAl2−2xO4 (x = 0.00–0.10) nanospinel oxides (NSOs) were synthesized via the sol–gel route. XRD confirmed the formation of a pure cubic spinel structure with crystallite sizes ranging from 8.4 to 11 nm, while TEM, HR-TEM, SEM, and EDX analyses validated the cubic morphology and homogeneous chemical composition. The dielectric and electrical properties of Mo→ZnAl2O4 NSOs were systematically investigated across a wide frequency range (100 Hz–1 MHz) and temperature window (20–120 °C). AC conductivity followed Jonscher’s universal power law, confirming a correlated barrier hopping (CBH) mechanism, where electron transport occurs via hopping between localized states. Mo doping significantly enhanced conductivity, with nearly an order of magnitude improvement up to the optimal doping level of x = 0.06, attributed to oxygen vacancies and defect dipoles that facilitate polaron hopping between Mo6+/Mo5+ and Zn2+/Zn3+ sites. The activation energy (Ea) increased with doping, peaking at ~ 0.0686 eV for x = 0.06, and subsequently decreased at higher doping levels, suggesting a transition from optimized defect-assisted conduction to defect saturation. The dielectric constant rose from x = 0.00 to x = 0.06 at 120 °C, accompanied by moderate dielectric loss, reflecting enhanced dipolar relaxation and thermally activated charge carrier hopping. Impedance spectroscopy revealed depressed semicircular arcs and Warburg tails, confirming non-ideal Debye relaxation, grain boundary effects, and diffusion-limited transport. These findings demonstrate that controlled Mo substitution in ZnAl2O4 nanospinel oxides can effectively tailor conduction and dielectric properties, making them promising candidates for dielectric and energy storage applications.