Divalent ion doping in CaFe₂O₄: A strategy for enhancing electrical conductivity in energy storage materials

IF 3 4区 材料科学 Q3 CHEMISTRY, PHYSICAL
M. Nadeem Madni , Farooq Ahmad , Muhammad Danish , M. Jahangeer , M.U. Islam , Muhammad Adnan , Shahid Atiq , Abdul Shakoor , Ahmed Althobaiti
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Abstract

This study investigates the microstructural and electrical properties of CaFe₂O₄ concentrating on cations' distribution in its spinel structure regarding tetrahedral and octahedral sites. This is achieved by substituting Ca2+ with divalent metal ions like Co2+, Ni2+, Cu2+, and Zn2+. The transition metal-doped CaFe₂O₄ (Ca-ferrite) and other samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, dielectric measurements, and electrical resistivity analysis. The creation of a single-phase orthorhombic structure (space group Pnam, No. 62) devoid of impurity phases was validated by XRD patterns, with 64–27 nm crystallite sizes, depending on the dopant (from Co to Zn). SEM micrographs revealed inhomogeneous, agglomerated grains with sizes varying between 95 nm and 35 nm. EDX analysis verified the expected elemental composition, free of impurities. Dielectric characteristics were assessed between 20 Hz and 1 MHz in frequency, adhering to the Maxwell-Wagner polarization model. A notable decrease in DC electrical resistivity was observed, from 4.9 × 107 Ω-cm in undoped CaFe₂O₄ to 3.2 × 106 Ω-cm in Zn-doped samples. This reduction in resistivity is attributed to substituting Ca2+ with transition metal ions of smaller ionic radii, which reduces the hopping length and enhances electron mobility, thereby improving electrical conductivity. These findings suggest that CaFe₂O₄, particularly when doped with conductive elements like Cu and Zn, holds significant potential for application in energy storage devices.

Abstract Image

在硫酸钙中掺杂二价离子:提高储能材料导电性的策略
本文研究了硫酸钙的显微结构和电学性质,重点研究了四面体和八面体尖晶石结构中阳离子的分布。这是通过用二价金属离子如Co2+、Ni2+、Cu2+和Zn2+取代Ca2+来实现的。利用x射线衍射(XRD)、扫描电子显微镜(SEM)、能量色散x射线能谱(EDX)、拉曼光谱、介电测量和电阻率分析对过渡金属掺杂的CaFe₂O₄(Ca-ferrite)等样品进行了表征。通过XRD谱图验证了无杂质相的单相正交结构(空间群Pnam, No. 62),根据掺杂物(从Co到Zn)的不同,晶粒尺寸为64-27 nm。扫描电镜显示,颗粒大小在95 nm到35 nm之间,不均匀,团聚。EDX分析证实了预期的元素组成,无杂质。根据麦克斯韦-瓦格纳极化模型,在20 Hz和1 MHz频率范围内评估介电特性。观察到直流电阻率显著降低,从未掺杂的硫酸钙的4.9 × 107 Ω-cm到掺杂锌的3.2 × 106 Ω-cm。这种电阻率的降低是由于用较小离子半径的过渡金属离子取代Ca2+,从而减少了跳变长度并增强了电子迁移率,从而提高了电导率。这些发现表明,硫酸钙,特别是当掺杂导电元素如Cu和Zn时,在储能设备中具有巨大的应用潜力。
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来源期刊
Solid State Ionics
Solid State Ionics 物理-物理:凝聚态物理
CiteScore
6.10
自引率
3.10%
发文量
152
审稿时长
58 days
期刊介绍: This interdisciplinary journal is devoted to the physics, chemistry and materials science of diffusion, mass transport, and reactivity of solids. The major part of each issue is devoted to articles on: (i) physics and chemistry of defects in solids; (ii) reactions in and on solids, e.g. intercalation, corrosion, oxidation, sintering; (iii) ion transport measurements, mechanisms and theory; (iv) solid state electrochemistry; (v) ionically-electronically mixed conducting solids. Related technological applications are also included, provided their characteristics are interpreted in terms of the basic solid state properties. Review papers and relevant symposium proceedings are welcome.
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