Scholarlink

<p>The present study investigates the effect of Strontium (Sr) doping in a series of materials having nominal composition Y<sub>1-<i>x</i></sub>Sr<sub><i>x</i></sub>Fe<sub>0.5</sub>Co<sub>0.5</sub>O<sub>3</sub> (x = 0.1,0.2), synthesized from high-purity nitrates using the solid-state reaction method. X-ray diffractometry (XRD) studies confirms that the material exhibits a single-phase orthorhombic perovskite structure with Pnma space group symmetry exhibiting a consistent peak shift (Δ2θ = 0.15–0.35°) and increased lattice strain, indicating Sr-induced structural deformation. Furthermore, Rietveld refinement of the x-ray data verifies that the Sr<sup>2+</sup> ions replace the Y<sup>3+</sup> ions at the A-site of perovskite lattice in YFe<sub>0.5</sub>Co<sub>0.5</sub>O<sub>3</sub>. The charge imbalance caused by Sr<sup>2⁺</sup> substitution at the Y<sup>3⁺</sup> site is compensated through the creation of oxygen vacancies and by creation of mixed valence states of Fe<sup>3⁺</sup>/Fe<sup>2⁺</sup> and Co<sup>3⁺</sup>/Co<sup>2⁺</sup>. The presence of these defects increases the concentration of charge carriers, concurrently leading to lattice disorder and the localization of carriers. Additionally, Field Effect Scanning Microscopy (FESEM) investigations reveal that the synthesized materials have porous microstructure with crystallite sizes ranging from 160 to 240&#xa0;nm. Moreover, the dielectric response exhibits negative permittivity (ε′ &lt; 0) within the frequency range of 104–105&#xa0;Hz. This behavior can be explained by defect-mediated polarization mechanisms, specifically Maxwell–Wagner interfacial polarization and localized hopping conduction, instead of true metallic transport. Impedance analysis demonstrates a predominant semicircular response in Nyquist plots, whereas the Z″ versus frequency spectra display two relaxation peaks that correspond to contributions from grain and grain boundary effects. The relaxation time is approximately in the range of 10⁻⁸ to 10⁻⁷ seconds. The relaxation peak frequency exhibits a nearly constant value across the temperature range of 383–1083&#xa0;K, suggesting a non-thermally activated relaxation behavior. An explanation of the observed negative permittivity behavior has been provided using the Drude-Lorentz model. Overall, lattice strain and oxygen vacancies have a significant impact on the small polaron hopping between Fe3⁺/Fe2⁺ and Co<sup>3⁺</sup>/Co<sup>2⁺</sup> states that governs the conduction process. The metamaterial-like dielectric response shown at low frequencies shows that this system might be useful for electromagnetic shielding and adjustable dielectric devices.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Negative permittivity behavior in Sr and Co co-doped YFeO3 ceramic

  • 期刊论文

  • 发表日期：

    2026年5月4日

查看全文
  • Priya Dhuria,
  • Satnam Singh Bhamra,
  • Jasbir Singh Hundal

摘要

The present study investigates the effect of Strontium (Sr) doping in a series of materials having nominal composition Y1-xSrxFe0.5Co0.5O3 (x = 0.1,0.2), synthesized from high-purity nitrates using the solid-state reaction method. X-ray diffractometry (XRD) studies confirms that the material exhibits a single-phase orthorhombic perovskite structure with Pnma space group symmetry exhibiting a consistent peak shift (Δ2θ = 0.15–0.35°) and increased lattice strain, indicating Sr-induced structural deformation. Furthermore, Rietveld refinement of the x-ray data verifies that the Sr2+ ions replace the Y3+ ions at the A-site of perovskite lattice in YFe0.5Co0.5O3. The charge imbalance caused by Sr2⁺ substitution at the Y3⁺ site is compensated through the creation of oxygen vacancies and by creation of mixed valence states of Fe3⁺/Fe2⁺ and Co3⁺/Co2⁺. The presence of these defects increases the concentration of charge carriers, concurrently leading to lattice disorder and the localization of carriers. Additionally, Field Effect Scanning Microscopy (FESEM) investigations reveal that the synthesized materials have porous microstructure with crystallite sizes ranging from 160 to 240 nm. Moreover, the dielectric response exhibits negative permittivity (ε′ < 0) within the frequency range of 104–105 Hz. This behavior can be explained by defect-mediated polarization mechanisms, specifically Maxwell–Wagner interfacial polarization and localized hopping conduction, instead of true metallic transport. Impedance analysis demonstrates a predominant semicircular response in Nyquist plots, whereas the Z″ versus frequency spectra display two relaxation peaks that correspond to contributions from grain and grain boundary effects. The relaxation time is approximately in the range of 10⁻⁸ to 10⁻⁷ seconds. The relaxation peak frequency exhibits a nearly constant value across the temperature range of 383–1083 K, suggesting a non-thermally activated relaxation behavior. An explanation of the observed negative permittivity behavior has been provided using the Drude-Lorentz model. Overall, lattice strain and oxygen vacancies have a significant impact on the small polaron hopping between Fe3⁺/Fe2⁺ and Co3⁺/Co2⁺ states that governs the conduction process. The metamaterial-like dielectric response shown at low frequencies shows that this system might be useful for electromagnetic shielding and adjustable dielectric devices.