Research On Up/Down Conversion Luminescence Properties Of Yb³⁺/Er³⁺(Tm³⁺)/Sc³⁺, Er³⁺/Eu³⁺ Doped NaBiF₄

Rare earth luminescent nanocrystals have unique photo-luminescence properties due to unique 4f electronic structure of rare earth elements.Rare earth fluorides with low phonon energy are currently great substrate materials.Due to their high electronegativity,low phonon energy,low toxicity,strong ability to penetrate tissue cells,and strong resistance to photobleaching,Ln³⁺doped fluorides upconversion luminescent materials are widely used in solar cells,photothermal diagnosis and treatments,biological imagings,biological probes and other fields.In recent years,it has been found that the cost of Bi（NO₃）₃ is lower than most rare earth compounds.In order to achieve the purpose of cost savings,replacing the common rare earth fluorides such as Na REF₄（RE=Yb,Y,Gd,Sc,etc.）with NaBiF₄ as matrix materials can effectively reduce the cost of raw materials.In this thesis,NaBiF₄ are used as matrix materials,which doped with different rare earth ions(Yb³⁺,Er³⁺,Tm³⁺,Sc³⁺,Eu³⁺)to achieve enhanced up-conversion luminescence and the color transformation of down-conversion luminescence.The main contents are as follows:1、Pure hexagonal NaBiF₄:20mol%Yb³⁺,2mol%Er³⁺(0.5mol%Tm³⁺),xmol%Sc³⁺（x=0,1.5,2.5,5,7.5,10）phosphors were synthesized by solvothermal method with PVP at 190℃for 12 hours.Under 980 nm NIR light irradiation,NaBiF₄:Yb³⁺/Er³⁺(Tm³⁺)/Sc³⁺phosphors showed intense UC luminescence.Through the Sc³⁺ions doping,the enhancement in UC emission intensities was observed and the optimal doping concentration for Sc³⁺ions was revealed to be 2.5 mol%.2、NaBiF₄:1mol%Er³⁺,xmol%Eu³⁺（x=0,2,4,6,8,10）phosphors were synthesized by solvothermal method.The luminescent color of the phosphors can be changed by changing the doping concentration of Eu³⁺ions.Under the excitation of 377 nm ultraviolet light,the luminescent color of the samples changed from green to yellow.Under the excitation of 394 nm ultraviolet light,the luminescent color of the samples changed from blue to orange-red.