Study On Aluminate Fluorescent Ceramics With Garnet Structure

White LED（Light Emitting Diode）as a new type of solid-state lighting technology,in recent years has made rapid development.The current market LED packaging method is mainly composed of phosphors and organic resin/silicone mixed,which has poor thermal stability,easy aging,low thermal conductivity and other issues.Compared with resin/silicone encapsulated phosphors,fluorescent ceramics have more excellent thermal,mechanical and optical properties,and have attracted more and more attention in the application of high-power white LED.In this paper,YAG(Y₃Al₅O₁₂)-based phosphors doped with rare earth ions were systematically studied,and fluorescent ceramics and composite fluorescent ceramics were prepared on this basis.The samples were tested by X ray diffraction（XRD）,fluorescence spectrum,Scanning electron microscopy（SEM）,temperature variation spectrum and fluorescence lifetime,and the morphology,structure and luminescence properties of the samples were analyzed.The main research contents and results are as follows:（1）YAG-based phosphor was prepared by high-temperature solid phase method.The optimal sintering temperature was 1550°C,the optimal holding time was 6 h,and the flux was 0.04 wt%H₃BO₃.On this basis,rare earth ions were introduced to change the matrix structure and luminescent center type of YAG:Ce³⁺phosphor,and to study their effects on the phase structure,luminescence properties and particle morphology of phosphors.First of all,Gd³⁺,Lu³⁺,La³⁺replaced Y³⁺in YAG:Ce³⁺,and comparative analysis showed that when the amount of Lu³⁺was introduced 0.10 mol/L,the luminous intensity of Y_2.84Lu_0.1Al₅O₁₂:0.06Ce³⁺phosphor samples had the strongest luminous intensity and the longest fluorescence life,and the luminous intensity at 150°C was 89%of the room temperature.Later,on the basis of doping Lu³⁺,the activated ion Sm³⁺was introduced.The results showed that the emission spectrum had a small redshift after the introduction of Sm³⁺,and the characteristic emission peak of Sm³⁺was added at 620 nm,which increased the red light component in the spectrum to a certain extent.（2）Lu³⁺doped Y_2.84Lu_0.1Al₅O₁₂:0.06Ce³⁺fluorescent ceramics were prepared by vacuum sintering.The effects of sintering temperature,holding time,sintering additive type and concentration,and annealing treatment on the optical properties of Y_2.84Lu_0.1Al₅O₁₂:0.06Ce³⁺fluorescent ceramics were studied.The results show that when the sintering temperature is 1750°C,the holding time is 10 h,the sintering auxiliary is 0.02 wt%Mg O,0.75 wt%TEOS,the annealing treatment temperature is 1450°C and the heat preservation is 6 h,the luminescence,transmittance and morphology of the samples are the best.（3）Y_2.84Lu_0.1Al₅O₁₂:0.06Ce³⁺/Sr Al Si N₃:Eu²⁺composite fluorescent ceramics were prepared by screen printing combined with laser ablation.The results show that screen printing combined with laser ablation technology can obtain all-inorganic fluorescent ceramic composites.With the increase of the number of Sr Al Si N₃:Eu²⁺phosphor printing times,the luminous intensity of the red area in the emission spectrum gradually increased,and the effective regulation of the spectrum was realized.When the LED device is packaged with blue chip,the color temperature can vary from 3383 K to 9761 K,and the color coordinate can vary from（0.311,0.243）to（0.411,0.371）.When the package power is3.5 W,the maximum luminous efficiency can reach 148 lm/W,and the color rendering index can reach 90.