Lithium ion codoping effect on structural, morphological and photoluminescence spectroscopy of Lu3Al5O12: Ce3+ garnet powder material synthetized by sol gel method

Monovalent lithium (Li+) ion codoped Lu3Al5O12:Ce3+ (LuAG:Ce) powder garnet phosphors were successfully synthesized using a simple sol-gel method. The effect of different Li+ content, namely 1, 3, 5, 7, 9, 11, 15 at.%, on the structural, morphological and photoluminescence properties were investigated. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy-Dispersive X-ray Spectroscopy (EDS), as well as room temperature steady-state and time-resolved photoluminescence spectroscopy were used to characterize the samples. XRD patterns analysis showed that all powder samples crystallized in cubic garnet phase, with space group symmetry Ia3d, the crystallite size decreased as the Li+ co-doping concentration increased. Density Functional Theory (DFT) calculations indicated that Li+ ions in LuAG are predominantly localized at Al3+ (24d) site. FE-SEM showed that the addition of Li altered the morphology of the powder materials. Furthermore, all samples reveal a strong broad green–yellow emission band ranging from 450 to 650 nm, with decay time on the order of tens of nanoseconds, This emission was associated with the Electric Dipole (ED) 5d−4f radiative transition, allowed by the parity and spin of the Ce3+ ions. The photoluminescence emission and excitation spectra, as well as decay times were examined as a function of Li+ content, and compared with those of a Lu3Al5O12 single crystal grown by Czochralski method. Additionally, the determined radiative lifetime values of Ce3+ embedded in dielectric LuAG material were used to discuss the local field effect, based on both virtual (VC) or real (RC) cavity models.