Abstract

By using the solution combustion method and urea as a fuel, we synthesized aluminate nano-powders Al₂XO₄ (X = Cd, Ni and Co) to study the effects of the cation type on the chemical bonding, the structural and the optical properties of these materials through the X-ray diffraction (XRD) technique, UV–visible diffuse reflectance spectroscopy (UV–Vis), and Fourier transform infrared (FTIR) spectroscopy. The analysis of the XRD patterns shows the formation of spinel-type crystallites in the cubic crystal structure with the space group Fd-3 m (N°227) for all Al₂XO₄ samples, the average size crystallites increases from 38.55 to 45.86 nm, while the lattice constant decreases from 8.046 to 8.089 Å when the cation type is changed from Ni, Cd to Co. The FT-IR spectrums show that the principal absorption peaks are located in the region 400–745 cm⁻¹, those peaks are attributed to the aluminates in agreement with the XRD analysis. Besides, the slight shift the principal absorption peaks toward longer wavenumbers is due to the low electronegativity of Cd compared to the others two cations. The optical bandgap was determined through the analysis of the UV–Vis spectrum, the obtained values are 3.78, 3.82 and 3.75 eV for Al₂CdO₄, Al₂NiO₄ and Al₂CoO₄ respectively. The optical bandgap is assigned to charge transfer O²⁻: 2p → X²⁺: d orbital, the obtained findings show that the herein-studied spinels are a promising candidate for optoelectronic and photocatalytic applications.

中文翻译：

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溶液燃烧法合成纳米铝酸盐尖晶石Al2XO4（X=Cd、Ni、Co）的制备及光谱研究

摘要

采用溶液燃烧法，以尿素为燃料，合成了铝酸盐纳米粉体Al ₂ XO ₄ (X=Cd、Ni和Co)，研究了阳离子类型对其化学键合、结构和光学性能的影响。通过 X 射线衍射 (XRD) 技术、紫外可见漫反射光谱 (UV-Vis) 和傅里叶变换红外 (FTIR) 光谱对这些材料进行分析。 XRD图谱分析表明，所有Al ₂ XO ₄样品均在空间群Fd-3 m (N°227)的立方晶体结构中形成了尖晶石型微晶，平均微晶尺寸从38.55 nm增加至45.86 nm。 ，而当阳离子类型从Ni、Cd变为Co时，晶格常数从8.046减小到8.089 Å。FT-IR光谱显示主吸收峰位于400-745 cm ^-1区域，这些峰为归因于铝酸盐，与 XRD 分析一致。此外，主吸收峰向较长波数的轻微移动是由于与其他两种阳离子相比，Cd 的电负性较低。通过紫外-可见光谱分析确定了Al ₂ CdO ₄、Al ₂ NiO ₄和Al ₂ CoO ₄的光学带隙值分别为3.78、3.82和3.75 eV 。光学带隙被分配给电荷转移O ²⁻ : 2p → X ²⁺ : d轨道，所得结果表明本文研究的尖晶石是光电和光催化应用的有希望的候选者。