Influence of non-magnetic ions doping on structural, morphological, optical, and magnetic properties of nanocrystalline zinc oxide powders

Abstract

In this research study, nanocrystalline non-magnetic ion-doped zinc oxide powders are synthesized through sol-gel auto combustion with a variety of different ions (Mg, Al, and Ca) at a range of concentrations (0, 5%, 10%, 20% mol). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), filed-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), UV–visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL), and vibrating sample magnetometry (VSM) were then used to investigate the calcined products, whereupon the structures, chemical bonds, surface texture, chemical composition, morphologies, particle size, surface elemental composition, electronic state, optical and fluorescence properties including magnetism were reported for each of the samples. From XRD it could be determined that the introduction of minuscule quantities of magnesium and calcium ions to the zinc oxide powder produced solutions of hexagonal solid MgZnO and CaZnO, while composites of Mg/ZnO, CaO/ZnO, Al2O3/ZnO could also be observed, without impurity phases. Textural properties of these modified samples observed from SEM, FE-SEM, and TEM were superior to that of the pure ZnO. XPS studies confirmed the substitution of Zn2+ by Mg2+ and Ca2+ for the samples of low doping concentration. UV-DRS analysis showed that samples which had been optimally modified exhibited improved levels of absorption when compared to visible spectral observations of the pure sample. In comparison to the pure sample, the modified samples also showed higher bandgap energy (Eg). In the pure sample, violet and blue emission bands were seen in the PL spectra ranging from 350 to 430 nm, but these emissions showed significant changes in intensity as the concentration of non-magnetic ions was increased. Furthermore, VSM results revealed that diamagnetism of zinc oxide can be adjusted through the introduction of non-magnetic ions to paramagnetism and ferromagnetism.