Fabrication And Luminescent Properties Of Eu³⁺-doped LaF₃Nanoparticles

Rare earth luminescent materials have many potential applications, such as lighting, communications, display technology, solar cells and so on, due to their special spectral structure and excellent optical performance. Rare earth fluoride is a kind of excellent optical matrix material because of their low phonon energy, environmental stability and adequate thermal, therefore the LaF3matrix rare earth doped luminescent materials has important research value.In this work, Eu3+-doped LaF3(LaF3:Eu3+) nanocrystals were synthesized using a low temperature solvothermal method. Well-dispersed nanoparticles with an average size of30nm and a hexagonal shape were obtained. The influences of Eu3+ions concentration, reaction temperature and time on the structure and luminescence of LaF3:Eu3+nanoparticles were investigated. It has been concluded that Eu3+ions are located at sites with inversion symmetry in LaF3lattice and the concentration quenching of the Eu3+ions is15mol%. Higher temperature and longer reaction time can promote grain growth and improve the crystallinity of the nanoparticles. Moreover, with the increase of the solvothermal temperature, the luminescence was obviously enhanced.The effect of thermal annealing on LaF3:Eu3+nanocrystals phase structures and luminescence properties were also studied. It was found that a sufficiently high annealing temperature is required for the transformation of LaF3to LaOF. LaOF phase started to be formed after annealing at500℃for as short as5min, and higher annealing temperatures and low Eu3+ions concentration led to a larger amount of LaOF formed. With the increase of the formation of LaOF, the luminescence was greatly enhanced. Strong O2-â†'Eu3+charge transfer band was present in these samples annealed and the relative intensity of the charge transfer band was enhanced with the increase of the LaOF, and greatly enhanced7Foâ†'5D2transition of Eu3+was also observed.