Impact of indium doping on the structural, optical and radiation shielding characteristics of nano/quantum dots ZnAl2-xInxO4

Abstract

ZnAl_2-xIn_xO₄ (x=0.0, 0.1, 0.15, 0.2, 0.25) samples were prepared employing the solid-state reaction approach. The structural inspection, utilizing Rietveld refinement and synchrotron x-ray diffraction patterns, revealed the substantial solubility threshold of indium within the ZnAl₂O₄ (ZAO) matrix and enabled the assessment of the inversion parameter, which expresses the distribution of cations among the tetrahedral and octahedral sites within the spinel conformation. The cation distribution fingerprint appeared on the Fourier transform infrared spectroscopy (FTIR) spectra. The transmission electron microscopy (TEM) technique revealed a little variation in particle size with an average value of 6 nm as determined from Rietveld x-ray analysis. Field emission scanning electron microscopy (FESEM) technique and energy dispersive X-ray spectroscopy (EDS) analysis were used to spot the morphology and elements inside the samples. The optical bandgap energy E_g value for ZAO is 4.43 eV and diminished to 4.41, 4.22, 4.22 and 3.96 eV for indium doping levels of x=0.1, 0.15, 0.2, and 0.25, respectively. Upon doping, optical absorption is significantly elevated in the ultraviolet region. CIE chromaticity diagrams revealed that the samples displayed cyan-blue colors depending on the amount of indium doping. The linear (LAC) and mass attenuation coefficient (MAC) values for all samples were maximum at the minimal energy value of 0.015 MeV. The LAC is elevated from 148 cm^-1 to 246 cm^-1 and MAC from 31.9 to 47.7 cm²/g for x=0.0 and 0.25, respectively. The half value layers (HVL), tenth value layers (TVL) and mean free path (MFP) values diminished as ZAO was doped with indium, indicating that the doped samples possess superior shielding properties compared to undoped ZAO. ZnAl₂O₄ doped with 0.1 or 0.15 indium disclosed marvels photoluminescence and has potential applications in phosphors, especially in light-emitting devices and displays.