Preparation And Properties Of Rare Earth Ions Doped YBO₃ Phosphors With Tunable Color For WLED

In the past decades,inorganic luminescent materials doped with rare earth ions have attracted much attention and research in the fields of LED lighting,biomedicine,solar cells,optical sensing and high-energy laser weapons due to their unique chemical stability and luminescence properties.Phosphors prepared by doping trivalent rare earth ions have many unique advantages,such as rich spectral lines in the visible region,narrow spectral band,concentrated luminescence energy,good high temperature resistance,high luminescence efficiency and adaption to high-load environment.Compared with other inorganic matrix materials,YBO₃ has the advantages of high chemical stability,low cost,easy synthesis and special optical damage threshold,which makes it an ideal matrix material doped with rare earth ion activators.Although the preparation of phosphors based on YBO₃ doped with various rare earth ions has been studied widely,the preparation of rare earth ions co-doped YBO₃ matrix with tunable color is rarely reported.In this thesis,a simple hydrothermal method was used to prepare YBO₃-based three-primary color rare earth ion phosphor and explore its application in white LED（WLED）.YBO₃:x%Ce³⁺;YBO₃:1%Ce³⁺,x%Tb³⁺;YBO₃:1%Ce³⁺,x%Eu³⁺;YBO₃:3%Tb³⁺,x%Eu³⁺;YBO₃:1%Ce³⁺,3%Tb³⁺,x%Eu³⁺phosphors were prepared by hydrothermal method.By changing the atomic ratio of Ce³⁺,Tb³⁺,Eu³⁺to control the luminescent color of the phosphor in order to prepare color-tunable tricolor rare earth ion-doped YBO₃phosphors and apply them to the field of LED display lighting.The luminescence properties,phase composition and surface morphology of the phosphors were analyzed by PL,XRD,SEM characterization methods.Meanwhile,LED devices based on（In）Ga N chips were prepared.The experimental conclusions are as follows:（1）The phosphors prepared by excessive boric acid(RE³⁺:H₃BO₃=1:4)has a hexagonal crystal structure.It has more regular spherical morphology,better crystallinity and stronger luminescence intensity.（2）YBO₃:x%Ce³⁺（x=0.5,1,2,3,4）phosphor presents a spherical shape with uniform size and full particles,and the surface of the spherical particles is covered with a small amount of lamellar particles.When the value of x is 1,the crystallization performance,luminous intensity,quantum efficiency and fluorescence lifetime of the sample are the highest.（3）YBO₃:1%Ce³⁺,x%Tb³⁺（x=0,0.5,1,2,3）phosphors are hexagonal crystal structures.With the increase of Tb³⁺doping amount,the crystallinity of the sample increases continuously,and the surface morphology consists of full but not dense spherical particles composed of lamellar grains,which gradually become secondary lamellar clearly visible,with small gaps and compact packing persimmon shape.The luminescence properties indicate that there is energy transfer between Ce³⁺and Tb³⁺.（4）YBO₃:1%Ce³⁺,x%Eu³⁺（x=0,0.5,1,2,3）phosphors are hexagonal crystal structures.With the increase of Eu³⁺doping amount,the crystallization properties of the samples first increased and then decreased,and the surface morphology changed from full but not dense spherical particles composed of lamellar grains to dense spherical particles with well-defined layers.The luminescence properties indicate that there is metal-metal charge transfer between Ce³⁺and Eu³⁺.（5）YBO₃:3%Tb³⁺,x%Eu³⁺（x=0,0.5,1,2,3）phosphors have a hexagonal crystal structure,and the crystallinity increased with the increase of Eu³⁺doping amount.All the samples were made up of plump spherical particles.The luminescence properties indicate that energy transfer exists between Tb³⁺and Eu³⁺.（6）YBO₃:1%Ce³⁺,3%Tb³⁺,x%Eu³⁺（x=0,0.1,0.5,1,2,3）phosphors belong to the hexagonal crystal phase crystal structure,and the crystallization performance is good.With increasing amount of Eu³⁺,the surface morphology changes from particles with non-uniform size,thin secondary lamella structure and uniform voids to spherical particles with clear secondary lamellae,uniform size and full particles with the increase of Eu³⁺.The luminescence properties indicate that there is energy transfer between Ce³⁺,Tb³⁺and Eu³⁺.（7）Ln³⁺co-doped YBO₃-based phosphors can achieve white light emission and can be used in WLEDs.