The Structure And Properties Of Fluoride-based Up-conversion Luminescent Materials

Rare earth doped up-conversion luminescent materials have always been a hot research material,especially the up-conversion luminescent materials based on fluoride,which have been widely studied and applied because of their low phonon energy,good chemical stability,high luminous efficiency and luminous intensity.Therefore,in this paper,a series of studies on rare earth ion doped fluoride-based up-conversion luminescent materials were carried out,and XRD,SEM,fluorescence emission spectrum and Fourier infrared spectrum were tested.According to the results,the influence of the structure of the sample on the luminescent properties was analyzed.Based on the prepared fluoride-based solid solution phosphors,a fluorescent coating was successfully prepared by screen printing combined with laser ablation,which expanded the application of up-conversion phosphors.The main research contents and results are as follows:（1）Sr F₂:Er³⁺,Yb³⁺up-conversion phosphors were prepared by high temperature solid-state method using Sr F₂ as matrix material,Er³⁺as activator and Yb³⁺as sensitizer.The effects of sintering temperature,holding time and rare earth ion doping concentration on the luminescence properties were studied.The optimum sintering temperature was650℃,the optimum holding time was 1.5h,and the molar doping ratio of Er³⁺/Yb³⁺was2:10.（2）Using Pb F₂ as the matrix material,Ba²⁺ions and Sr²⁺ions were introduced to replace the position of Pb²⁺ions to form a substitutional solid solution.The results show that Ba²⁺and Sr²⁺ions replace Pb²⁺ions to form solid solution,which causes the stretching vibration of chemical bonds in the lattice,improves the lattice asymmetry and adjusts the luminescence performance.The luminescence mechanism under 980nm,1064nm and1550nm laser excitation was studied.The green emission corresponds to the ²H_11/2→⁴I_5/2,⁴S_3/2→⁴I_15/2 transition of Er³⁺,and the red emission corresponds to the ²F_9/2→⁴I_15/2 transition of Er³⁺.（3）Fluorescent coatings were prepared by screen printing combined with laser ablation using transparent ink and(Pb_1-xBa_x)F₂:Er³⁺,Yb³⁺up-conversion phosphor as raw materials.The effects of the ratio of transparent ink to phosphor,the amount of ink diluent,laser ablation power and scanning speed on the luminescence properties of the fluorescent coating were studied by fluorescence spectrum test,variable temperature spectrum test and transmittance test.