El Shater R E, Awad A W, Abdel-Khalek E K, El-Bahnasawy H H, Meaz T M, Okba Ehab A
Physics Department, Faculty of Science, Tanta University, Tanta, 31527, Egypt.
Physics Department, Faculty of Science, Al-Azhar University, Nasr City, Cairo, 11884, Egypt.
Sci Rep. 2023 Sep 19;13(1):15482. doi: 10.1038/s41598-023-41214-1.
Two ferrite series were synthesized. One series has nanosize samples that have been prepared by the co-precipitation method, and the second series has the corresponding bulk samples that have been sintered at 1000 °C for 6 h. X-ray diffraction has been used to estimate the cubic spinel structure of both series. The crystallite size, theoretical density, and porosity of the nanomaterials are larger than those of the bulk materials. HRTEM analysis demonstrated the aggregation of nanoscale samples, including an average particle size of 9-22.5 nm. However, bulk specimens have a limited surface area. The agglomeration of the nanoparticles was seen in TEM images, in which the mean particle size was within the limit of the crystallite size (R) result and ranged from 14 to 20 nm. The appearance of the spinel phase in the samples was validated through Raman spectroscopy. Different cation occupation ratios in either tetrahedral or octahedral sites have been identified to be associated with an observable systematic shift and asymmetric flattening in Raman spectra with a variation in Cr concentration. The optical characterization was performed using the UV/Vis methodology, and the results reveal that the absorption cutoff frequency declines as the chromium content rises. It was also estimated that the optical bandgap averaged 3.6 eV for nanosamples and 4.6 eV for overall bulk materials. The highest photoluminescence emission was seen at wavelengths between λ = 415 and 460 nm. The photoluminescence emission peaks of both bulk and nanoscale materials were red-shifted. These results accurately reflect the corresponding energy gap values for almost the same ranges. Sintering leads to a rise in photoluminescence.
合成了两个铁氧体系列。一个系列具有通过共沉淀法制备的纳米尺寸样品，另一个系列具有在1000℃下烧结6小时的相应块状样品。已使用X射线衍射来估计两个系列的立方尖晶石结构。纳米材料的微晶尺寸、理论密度和孔隙率均大于块状材料。高分辨率透射电子显微镜（HRTEM）分析表明纳米级样品发生了聚集，平均粒径为9 - 22.5纳米。然而，块状样品的表面积有限。在透射电子显微镜（TEM）图像中可以看到纳米颗粒的团聚，其中平均粒径在微晶尺寸（R）结果的范围内，为14至20纳米。通过拉曼光谱验证了样品中尖晶石相的出现。已确定四面体或八面体位点中不同的阳离子占据率与拉曼光谱中随Cr浓度变化而出现的可观察到的系统位移和不对称变平有关。使用紫外/可见光谱法进行了光学表征，结果表明吸收截止频率随着铬含量的增加而下降。据估计，纳米样品的光学带隙平均为3.6电子伏特，整体块状材料的光学带隙平均为4.6电子伏特。在波长λ = 415至460纳米之间观察到最高的光致发光发射。块状和纳米级材料的光致发光发射峰均发生红移。这些结果准确地反映了几乎相同范围内相应的能隙值。烧结导致光致发光增强。
