Preparation And Properties Of Spherical Eu³⁺ Doped Phosphors By Ultrasonic Spray Drying

Eu3+doped rare earth oxide phosphors are widely used in various light-emitting devices as high-efficiency red light-emitting materials.Morphology and particle size are important factors affecting its luminous intensity.However,the main stream methods for preparing Eu3+doped rare earth oxide phosphors is solid state method which cannot effectively control the morphology,and a few controllable morphology preparation path such as wet chemically path is cumbersome and the cycle is too long.It is impossible to continuous produce product in one step.In order to solve the above problems,this thesis selects the oldest and most widely used three types of Eu3+doped rare earth oxide phosphors including YVO4:Eu3+,Y2O3:Eu3+and YAG:Eu3+as the target products and research objects.A novel spray drying method and the ultrasonic spray-drying method is used for the preparation path,and a spherical Eu3+doped rare earth oxide phosphor with controlled morphology and particle size is prepared by this method in one step,and the advantages and disadvantages of the preparation method are discussed.The main research contents and conclusions are as follows:1)A two-step preparation process combining hydrothermal method and spray drying method was successfully used to synthesize a spherical-like morphology YVO4:Eu3+/SiO2 composite with a particle size distribution of 1-7 ?m.Under the excitation light with a wavelength of 280 nm,strong emission peaks appeared at the wavelengths of 596 nm and 618 nm(red light),and the luminous intensity was significantly improved compared to the YVO4:Eu3+prepared by the hydrothermal method.The preparation process in this thesis will effectively simplify the traditional composite material synthesis steps,so it is expected to apply this process to industrial production and improve production efficiency.However,samples prepared by this method still have large particle size,irregular spherical shape,wide particle size distribution,etc.these shortcomings still need to be overcame.2)Spherical Y2O3:Eu3+rare earth oxide phosphors produced by one-step ultrasonic spray drying using a two-component solution as a precursor.The samples meet the industrial requirements in terms of structure,photoluminsence performance and color purity.The samples prepared by the ultrasonic spray drying method highly conform to the spherical morphology,the particle size is controllable,and the particle size is significantly lower than that of the samples synthesized by traditional spray drying,from 1?7 ?m to 1-2 ?n or even sub-microns.The ultrasonic spray drying method obviously improves the spray drying method and strengthens the advantages of the spray drying method in controlling the morphology,making up for the lack of excessive particle size of the sample prepared by the spray drying method,further simplifying operations and improving production efficiency.3)Spherical ternary rare earth oxide phosphor YAG:Eu3+was successfully prepared in one step by ultrasonic spray drying method using multi-component solution as precursor.The results of XRD and energy spectrum characterization shows that the expected product was obtained and heterogeneous phase didn't exist.Its morphology is regular and dense spherical,the particle size is in the range of 1-3 ?m,and the particle size distribution width is narrow.When 240 nm is used as the excitation wavelength,the emitted light confirms to the characteristic emission peak of Eu3+,and the luminous intensity is weaker than that of the sample prepared by the solid state reaction method,but the color purity is improved.The ultrasonic spray method greatly simplifies the preparation process and operation of sub-micron spherical ternary rare earth oxides,and enhances morphology and particle size control.It can be extended in industrial production and better the production efficiency.In summary,the ultrasonic spray drying method proposed in this thesis can continuously prepare micron/sub-micron Eu3+doped phosphors with excellent spherical morphology,well performance,small particle size with controllability.In addition,the ultrasonic spray drying method is one-step way,the loss rate of product is not high,and the production efficiency can be greatly improved.This novel method can provide new methods and ideas for other researchers or industrial producers on the control of phosphor morphology and the improvement of production efficiency.