Synthesis and microstructure of Co/Ni: MgGa2O4 nanoparticles

This report discusses the preparation and microstructure of Co/Ni co-doped MgGa2O4 nanoparticles. The nanoparticles with the size of 20–55 nm were synthesized by sol-gel method. The phase and crystallinity were confirmed by X-ray powder diffraction (XRD) pattern. The particle size was estimated according to XRD data and transmission electron microscopy. The electronic structure was studied using X-ray photoelectron spectroscopy (XPS). The XPS studies showed that Ga3+ ions possess tetrahedral and octahedral sites of spinel structure and the inverse degree (two times of the fraction of tetrahedral Ga3+ ions) has increased with the increase of the doping concentration of Co2+ and Ni2+ ions. For Co/Ni co-doped MgGa2O4, two broad absorption bands of 350~500 and 550~700 nm were observed in the absorption spectra. The broad band at 350~500 nm was assigned to the combination of the absorption of octahedral Co2+ and Ni2+ ions, whereas the absorption band at 550~700 nm is mainly due to tetrahedrally coordinated Co2+ ions and octahedrally coordinated Ni2+ ions.