Study On Optical Properties And Application Of Rare Earth Doped Up/Down Conversion Oxide Luminescent Materials

Rare earth doped micro-nano luminescent materials have attracted extensive attention in many applications,such as optical temperature sensing,cell imaging,medical treatment,anti-counterfeiting,solar cells and plant lamps,due to their narrow emission band,weak toxicity and long life.In order to improve the utilization rate of materials and meet the needs of production and life,the development and exploration of multifunctional materials is imperative.In addition,rare earth luminescent materials are still facing the dilemma of low doping concentration.The increase of doping concentration will reduce the distance between the dopants,which will inevitably enhance the interaction between the light centers,resulting in the weakening of the luminous intensity.Therefore,in order to achieve high concentration doping of rare earth ions,one of the methods is to design and adjust the lattice structure of the matrix material.Therefore,starting from the multifunctionality of rare earth luminescent materials,we first look for single-phase self-luminescent phosphors with double activators,so as to realize the dual-mode emission under the excitation of single ultraviolet light,and explore the structure,optical properties and related applications of the phosphors in detail.In addition,in order to construct up-conversion luminescent materials with high concentration doping,one of the requirements is to reduce the concentration quenching phenomenon of activator ions and increase the distance between dopants,so as to optimize the luminescent properties of up-conversion luminescent materials.The specific research contents include the following aspects:(1)CaEuAl₃O₇:Eu²⁺/Eu³⁺single-phase self-luminescent phosphors were successfully synthesized by high temperature solid phase method in carbon rod reduction atmosphere.Under the excitation of a single UV light(359nm),the broad blue emission of Eu²⁺ions and the sharp peaks of Eu³⁺ions can be realized simultaneously,and the emission spectra are consistent with the absorption spectra of chlorophyll and carotenoids.The thermal stability of CaEuAl₃O₇:Eu²⁺/Eu³⁺samples was obtained by calculating the relative intensity of all emission peaks and the change of color coordinates with temperature.Therefore,it has a great prospect to combine the sample with commercial UV chips to prepare LED devices in the application field of plant lamps.At the same time,the fluorescence intensity ratio temperature sensing properties of the non thermal coupling energy levels(5d?4f,⁵D₀?⁷F₂,⁵D₀?⁷F₄)of Eu²⁺and Eu³⁺are discussed,and a relatively high sensitivity of 6.90%K^-1is obtained.(2)Ba₆Gd₂Ti₄O₁₇oxide was also successfully synthesized by high temperature solid phase method.Through the analysis of crystal structure,the alternate arrangement of GdO₆and BaO₆polyhedra can increase the distance between the luminescent centers in the matrix,making the doping concentration of Er³⁺ions as high as 0.25.The mechanism of Er³⁺ions high concentration doping performance and luminescence mechanism were discussed in detail.Furthermore,in order to prove the influence of structural factors on Er³⁺doping,we also studied other non-layered BaGd₂O₄and BaGd₂ZnO₅oxides,and found that their optimal Er³⁺doping amount can only reach 0.05.The luminescent intensity,fluorescence lifetime,quantum efficiency and the relationship between luminescent intensity and pump power were compared and analyzed.