Structural and magnetic properties of Al-doped yttrium iron aluminum garnet and optical properties of Mn, Sr, Fe-doped ZnO prepared by solution combustion method

Abstract

The structural and magnetic properties of Al substituted yttrium-iron garnet (Y3AlxFe5-xO12, x = 0, 0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6 and 1.8) ceramic powders synthesized using solution combustion method were investigated. For low Al content, Al3+ ions have preference to occupy tetrahedral (Td) sites than the octahedral (Oh) sites. At higher Al content the distribution of Al tends towards a ratio of 3:2 at the tetrahedral:octahedral site. Increase in Al doping results in the decrease in the lattice parameter due to smaller size of Al3+ as compared to Fe3+ ion. All the studied samples show coral-network-like surface morphology. The saturation magnetization (MS) values decrease from ∼26.94 emu/g to ∼ 0.17 emu/g with increase in Al content from 0.0 to 1.8. Further addition of Al makes the sample paramagnetic at RT. Substitution of non-magnetic Al3+ reduces the saturation magnetization rapidly due to the decrease in the superexchange interaction in the crystal. Furthermore, solution combustion synthesis of Mn, Sr or Fe-doped zinc oxide ceramic samples was carried out. All the samples were characterized by XRD, SEM and UV-DRS. The magnetic order of Fe in ZnO lattice of the Fe-doped ZnO samples was characterized by Mössbauer spectroscopy. The X-ray diffractograms determine the solubility limits of dopant in the host (ZnO) lattice. Electron micrographs confirmed the spongy network nanostructure of all the samples. The bandgap of the samples was estimated from Tauc plots of corresponding UV-DRS spectra. The spongy (high surface area) and low bandgap of Fe-ZnO renders it as an important candidate for photocatalytic applications. Our results show that among all these samples, Fe-doped zinc oxide nanoparticles can be the most suitable candidate for photocatalytic applications.