Abstract

This work reports, thermal, structural, magnetic, electric, and dielectric investigations of the CoFe_2-xAl_xO₄ nanocrystals synthesized through eco-friendly green sol–gel auto-ignition route. X-ray diffractograms exposed the uni-phasic geometry with Fd3m^_\({\text{O}}_{{\text{h}}}^{7}\) space group. The standard crystallite sizes were found in between 24 and 44 nm, confirming the nano-crystalline dimension. FTIR analysis confirmed the two specific vibrational stretching bands corresponding to the spinel ferrite geometry. The surface topology of ferrite nanocrystals with size distribution was effectively observed from TEM micrographs. The magnetic study at room temperature showed lessening in saturation magnetization with rise in Al³⁺ concentrations, ascribed to the replacement of Fe³⁺ ions by paramagnetic Al³⁺ ions. The M–H loops showed the perfect loop of typical soft ferromagnetic behavior of the produced nano-ferrites. The saturation magnetization, coercivity, and magneto-crystalline anisotropy declines with the upsurge in Al³⁺ ions which is owing to the non-magnetic contamination in the magnetic matrix. The DC-electrical resistivity was enhanced with growing temperature along with Al³⁺ content x. The dielectric parameters boosted pointedly with Al³⁺ substitution and decline exponentially with a rise in frequency in compliance with ‘Koops’ phenomenological theory. All the outcomes show that Al³⁺ substitution influences the physical characteristics of cobalt ferrite nanocrystals which shows its suitability in various technological applications.

Graphic abstract

The graphical abstract presenting the synthesis reaction, TEM micrograph (along with crystallite size distribution) and M–H plots for CoFe_2-xAl_xO₄ nanocrystals.

中文翻译：

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CoFe 2-x Al x O 4纳米晶体的环保绿色合成与表征：结构，磁，电和介电性能分析

摘要

该工作报告了通过环保的绿色溶胶-凝胶自燃路线合成的CoFe _{2- x} Al _x O ₄纳米晶体的热，结构，磁，电和介电研究。X射线衍射图显示Fd3m ^_的单相几何^_ \（{\ text {O}} _ {{\ text {h}}} ^ {7} \）空间群。发现标准微晶尺寸在24至44nm之间，证实了纳米晶尺寸。FTIR分析证实了对应于尖晶石铁氧体几何形状的两个特定的振动拉伸带。从TEM显微照片可以有效地观察到具有尺寸分布的铁氧体纳米晶体的表面拓扑。在室温下将磁性研究中饱和磁化强度表现出减轻与上升的Al ³⁺浓度，归因于取代Fe ³⁺由顺磁Al离子³⁺离子。MH回路显示出所生产的纳米铁氧体的典型软铁磁行为的完美回路。随着Al的增加，饱和磁化强度，矫顽力和磁晶各向异性下降³⁺离子是由于磁性基质中的非磁性污染所致。随着温度的升高，Al ³⁺含量x增强了直流电阻率。根据“ Koops”现象学理论，介电参数随着Al ^3+的取代而显着提高，并且随着频率的升高呈指数下降。所有结果表明，Al ³⁺取代会影响钴铁氧体纳米晶体的物理特性，这表明其在各种技术应用中的适用性。

图形摘要

图形抽象呈现所述合成反应，TEM显微照片（与微晶尺寸分布一起）和M-H曲线为的CoFe _{2- X}的Al _X Ò ₄纳米晶体。