Preparation And Up-conversion Luminescence Characterization Of Fluoride Nano-crystal Glass

Up-conversion luminescence materials doped rare earth ions is paid much attention to in the field of rare earth luminescent materials all the time, it was widely applied in optical storage, optical communication system, night vision system, laser medical instruments and apparatus and sensing device, etc. The longer lifetime of excited state electron was required so that the excited electron can receive the exciting photon and transit to higher level. So the low phonon energy of host materials is critical.Fluoride glasses are highly desirable materials for up-conversion host glasses, with high transparency and high solubility for rare earth ions, lower phonon energy is most important. However, the application of fluoride glasses was rejected, because of the expensive price, poor stability, not easy to prepare general fiber. Oxide material doped with rare earth ions has satisfied chemical and mechanical properties, but phonon energy is too high to detect the up-conversion luminescence. Oxyfluoride materials are composed of fluoride micro-crystal which is inserted into oxide glass host. Rare earth ions were priority deposited into fluoride micro-crystal, with lower phonon energy environment. Because the oxidate was dispersed in the material, oxyfluoride materials have excellent chemical and mechanical properties, more easy to be prepared than the fluoride glasses or crystal. So oxyfluoride materials are highly desirable materials for optical amplification, up-conversion lasers and display devices.In the paper, a series of transparent oxy-fluoride glass-ceramics doped with Er³⁺ was prepared by sol-gel method, XRD pattern of the sample indicate the existence of LaF₃ micro-crystal. The particle diameter data was obtained through Scherrer Equation and SEM. The up-conversion properties and luminescence mechanism was investigated through the analysis to up-conversion spectra. The data indicate that up-conversion emission in the sample with 5wt% LaF₃ was not observed, the luminescent density increases with the increase of Er³⁺ions concentration in the sample with 10wt% LaF₃, but the luminescent density reduced in the sample of Er³⁺ ions concentration more than 1%, this reason result from concentration quench. The relationship between up-conversion luminescent density at 520, 540, 660nm and LD current was fitted under excitation of laser with 980 nm, double photon progress was proved. In the sample with 10% LaF₃ and l%Er³⁺, emission peak of green at 540nm is most strong, the luminescence process is due to the predominant relaxation of Er³⁺ from level ⁴F_3/2 to level ⁴S_3/2 and then energy transfer to ground state.