Sol–gel preparation and photoluminescence enhancement of Li+ and Eu3+ co-doped YPO4 nanophosphors

YPO4 nanoparticles with pure monoclinic phase were successfully synthesized by a simple sol–gel method using both citric acid (CA) and ethylene diamine tetraacetic acid (EDTA) as complexing agent. Techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), as well as high-resolution transmission electron microscopy (HRTEM) have been employed to characterize the as-synthesized nanoparticles. Furthermore, the photoluminescence (PL) characterization of the Li+ and Eu3+ co-doped YPO4 nanocrystals was carried out and the effects of the doping concentration of Li+ and Eu3+ active center concentration as well as calcination temperature on the PL properties have been studied in details. The results show that the incorporation of Li+ ions into the YPO4:Eu3+ lattice could induce a remarkable improvement of the PL intensity. The highest emission intensity was observed with the compound of 5%Li+ and 5%Eu3+ co-doped YPO4, whose brightness was increased by a factor of more than 2.5 in comparison with that of the YPO4:5%Eu.