Study On The Preparation And Performance Of Aluminosilicate System Phosphors And Glass Ceramics For White Light LEDs

White LEDs?white light-emitting diodes?has attracted much attention due to its advantages of energy saving,environmental protection and high efficiency,and is known as a green lighting source.At present,commercial white LEDs are packaged by blue LED chips and Y₃Al₅O₁₂:Ce³⁺yellow phosphors,which have the problems of low color rendering index,high color temperature and easy aging due to poor thermal conductivity of organic packaging materials.In order to solve these problems,we can consider the following two aspects:first,to replace YAG:Ce³⁺yellow phosphor with a combination of green phosphor and red phosphor with existing blue LED to improve color rendering index and lower color temperature;second,to obtain transparent glass ceramic with good luminescence and high transmittance,to overall replacement of phosphors and organic packaging materials,in conjunction with the popular near-ultraviolet LED chips,solves the problems in white LED packaging.Therefore,this paper conducts two researches.One is to replace the Lu³⁺-Al³⁺ion pair in Lu₃Al₅O₁₂:Ce³⁺with Ba²⁺-Si⁴⁺ion pair to prepare BaLu₂Al₄SiO₁₂:Ce³⁺green phosphor used in combination with blue LED;In terms of the preparation of Sr_1.07Al_2.2Si_1.8O₈:0.03Eu²⁺and Sr_1.09Al_2.2Si_1.8O₈:0.01Sm³⁺aluminosilicate system multilayer transparent glass ceramics,instead of phosphors and organic packaging materials,with UV LED.The main research contents and results are as follows:?1?BaLu_2-xAl₄SiO₁₂:xCe³⁺?x=0.01⁰.08?samples are pure rhodium aluminium garnet structure.Under 450 nm excitation,the emission intensity reaches its maximum at x=0.06.With the increase of Ce³⁺concentration,the emission spectrum shows a continuous red shift.At room temperature,the photoluminescent quantum yield of BaLu_1.94Al₄SiO₁₂:0.06Ce³⁺phosphors is determined to be 92.4%.The luminescent intensity of BaLu_1.94Al₄SiO₁₂:0.06Ce³⁺phosphor at200?decreased to 91.5%at room temperature.The color shift of BaLu_1.94Al₄SiO₁₂:0.06Ce³⁺phosphors is much smaller than that of commercial?Sr,Ba?₂SiO₄:Eu²⁺,and less than that of Lu₃Al₅O₁₂:Ce³⁺phosphors.?2?Aphosphor-convertedwhiteLEDdevicefabricatedbyusing BaLu_1.94Al₄SiO₁₂:0.06Ce³⁺as the green phosphor exhibits good optical performance with Ra=88.5,CCT=3562 K and CIE1931 chromaticity coordinates as?x=0.4041,y=0.3951?.BaLu_1.94Al₄SiO₁₂:0.06Ce³⁺has good optical properties used in white LED.?3?The optimum melting condition for Sr_1.07Al_2.2Si_1.8O₈:0.03Eu²⁺glass is 1 hour melting at1700?.The optimum crystallization temperature of glass is 1040?.After crystallization,the structure of the sample is SrAl₂Si₂O₈ with hexagonal phase.The longer the crystallization time is,the less the glass phase is,and the more the crystal phase is.The ceramic layer crystals grow along the c-axis in a rectangular columnar orientation.The sample has a ceramic/glass/ceramic sandwich structure.There is no obvious chemical difference in the distribution of each element between the ceramic zone and the glass zone,and the distribution is uniform.?4?Sr_1.07Al_2.2Si_1.8O₈:0.03Eu²⁺glasses have wide excitation peaks between 250-450nm for the glass samples crystallized for 4h,8h,12h and fully crystallized samples.There is only one broad emission peak at 495nm for the glass samples,and there are two emission peaks at 395 nm,477nm for the crystallized samples at 4h,8h,12h and the fully crystallized samples,respectively.With the increase of crystallization time,the intensity of excitation and emission peaks becomes stronger.The color of emission light gradually shifts from green region to blue region,and the quantum efficiency gradually increases.The transmittance of glass and crystalline samples for 4h,8h and12h exceeded 88.8%,86.8%,84.5%and 82.2%,respectively.?5?Sr_1.07Al_2.2Si_1.8O₈:0.03Eu²⁺and Sr_1.09Al_2.2Si_1.8O₈:0.01Sm³⁺double-layer glass crystalline transparent multilayer glass ceramics coated on 400nm purple chip.The color development index of white LED was 93.3,which could be used for white LED with high color development index.