Effect Of Concentration Of Trivalent Lanthanide Ions And Annealing Temperature On Luminescence Properties Of Multifluorides

Luminescent materials doped with Lanthanide ions have excellent optical properties,so they have important applications such as biomarkers,anti-counterfeiting technology and cancer treatment.Fluorides doped with lanthanide ions have become a research hotspot due to its well chemical stability.In this thesis,NaGdF₄,KGd₂F₇ and Sr₂Gd F₇ were used as host materials,and fluoride with different morphologies was obtained by solid-state reaction at medium temperature and precipitation reaction,and good characteristic luminescence by single-doping,co-doping and tri-doping of lanthanide ions.X-ray diffraction（XRD）,scanning electron microscope（SEM）,X-ray energy dispersive spectrometer（EDS）and photoluminescence（PL）were employed to study the phase structure,size and luminescence performance of the sample.The main conclusion listed as follows:1.A series of hexagonal NaGdF₄:xLn³⁺(Ln³⁺=Eu³⁺,Tb³⁺,Dy³⁺,Er³⁺,Tm³⁺)phosphors were prepared via solid-state reaction at medium temperature.The crystal structure,morphology and size of the products were studied,respectively.The luminescence properties of the sample were measured by multi-component doping lanthanide ions.It is found that,NaGdF₄:xLn³⁺phosphors show good characteristic luminescence by single-doping,co-doping and tri-doping.Under 273 nm ultraviolet light excitation,the trend of NaGdF₄:Eu³⁺,Tb³⁺phosphors color tones change from white to green by adjusting the doping concentration of Tb³⁺ions.In addition,the energy transfer has been studied in detail among Gd³⁺,Eu³⁺,Tb³⁺,Dy³⁺.2.A series of monoclinic KGd₂F₇:xLn³⁺(Ln³⁺=Eu³⁺,Tb³⁺,Dy³⁺)phosphors were prepared via precipitation reaction.It is found that,increasing annealing temperature can improve the size of KGd ₂F₇:x Eu³⁺sample and the emission intensit y of KGd ₂F₇:x Dy³⁺sample.Multicolor-tunable luminescence can be obtained by changing the chemical species and concentration of doping ions.In particularl y,KGd₂F₇:x Eu³⁺,0.02Tb³⁺,0.03Dy³⁺（x=0.01,0.05）sample annealed at 450℃has a white color emission.3.A series of Sr₂Gd F₇:xLn³⁺(Ln³⁺=Eu³⁺,Tb³⁺)phosphors were prepared via solid-state reaction at medium temperature.It is found that,the prepared Sr₂Gd F₇:xLn³⁺phosphors are tetragonal structure.Sr₂Gd F₇:x Eu³⁺show strong ⁵D_3,2,1→⁷F_1,2,3 transitions and weak ⁵D₀→⁷F_1,2transitions.Both unannealed and annealed Sr₂Gd F₇:0.02Eu³⁺samples have a white color emission.4.The chromaticit y coordinates of NaGdF₄:xLn³⁺（Ln=Eu,Tb,Dy,Er,Tm）,KGd₂F₇:xLn³⁺and Sr₂Gd F₇:xLn³⁺show that C IE chromaticit y diagram is related to host materials,doping concentration of lanthanide ions,annealing temperature,and multicolor-tunable luminescence phosphors can be obtained by changing these factors.