Low temperature synthesis of Lu3Al5-xGaxO12:Ce3+,Cr3+ powders using a sol-gel combustion process and its persistent luminescence properties

Lu3Al5-xGaxO12:Ce3+,Cr3+ powders were prepared using a sol-gel combustion (SGC) process. To clarify the effects of the preparation method on the phase formation and luminescence properties, Lu3Al3Ga2O12:Ce3+,Cr3+ powders were also prepared at different calcination temperatures using a solid-state reaction (SSR) process for comparison with the SGC process. The photoluminescence spectra of the synthesized powders consisted of strong bands of Ce3+ and weak peaks of Cr3+ within the green and red regions, respectively. A Lu3Al3Ga2O12:Ce3+,Cr3+ single phase can be achieved even at a low temperature of 1100 degrees C for the SGC process, whereas it is formed at a higher temperature of 1500 degrees C for the SSR process. The green emission intensities of the Lu3Al3Ga2O12:Ce3+,Cr3+ powders prepared using the SGC process were significantly higher than those prepared using the SSR process. This behavior can be explained using a crystal structure, particle morphology, and uniformity of the dopant distribution. For the Lu3Al5,GaxO12:Ce3+,Cr3+ powders prepared using the SGC process, increasing the Ga content caused an increase in the lattice constant, resulting in a blue-shift of the green band of Ce3+. The synthesized powders exhibited a persistent luminescence, which resulted from the trapping and de-trapping behaviors between the Ce3+ and Cr3+ ions. The longest persistent luminescence was observed for the Lu3Al3Ga2O12: Ce3+,Cr3+ powders prepared at 1700 degrees C using the SGC process, lasting approximately 40 min.