Study On The Preparation And Luminescenct Properties Of Borate Based Phosphors For White LED

White light-emitting diodes?WLED?is a kind of solid state lighting and display light source,whitch has great prospect of application because of its advantages of high efficiency,low energy,long life,environmental friendly,small volume,energy conservation and environmental protection.Compared with blue light LED and tricolor LED,the colour of LED excited by ultraviolet light can be controlled and even better.The performance of luminescent materials plays a key role in ultraviolet LED,and it is especially necessary to find suitable ultraviolet LEDs.Borate,which possess low synthesis temperature,good color rendering,small light attenuation,high luminous efficiency,simple synthetic process,stable chemical properties,etc,become a hot spot of research on fluorescent material,research on the borate based white LED phosphors is particularly important.In this article,Sr₅MgLa₂?BO₃?₆ and boric acid aluminum based phosphors have been synthesized by high temperature solid phase method,the lattice structure and the luminous performance of fluorescent material have been discussed.In the first chapter,the research status of white light LED,photoluminescence materials and luminescence mechanism,structure characteristics of borate and the research contents of the paper are briefly introduced.The second chapter introduces the methods of experiment and the characterization of the samples.The sixth chapter is the summary and prospect of the thesis.Chapter three,four and five are the main points of the thesis.The luminescence performance of the three systems is discussed respectively.In the third chapter,a series of activator single doped Sr₅MgLa₂?BO₃?₆:RE(RE=Eu³⁺,Dy³⁺,Tb³⁺,Sm³⁺,Bi³⁺,Ce³⁺,Pr³⁺,Tm³⁺)phosphors have been synthesized by using high temperature solid phase method.X-ray diffraction?XRD?and scanning electron microscope?SEM?are used to characterize the morphology and structure of the synthesized samples.Excitation and emission spectra are used to analyze the luminous performance of the phosphors,and the luminous color can been discussed according to CIE chromalicity coordinates.Results show that the synthesized samples are pure phase,each activator ion can been doped into the matrix and generate the corresponding characteristics,in which Dy³⁺ion emits white light,Eu³⁺,Sm³⁺and Pr³⁺red light,Bi³⁺,Ce³⁺and Tm³⁺purple light,Tb³⁺green light.In the fourth chapter,various activated ions codoped Sr₅MgLa₂?BO₃?₆ phosphors have been synthesized by using high temperature solid phase method,the synthesized phosphors include the following systems:Sr₅MgLa_2-x-y?BO₃?₆:xBi³⁺,yM(M=Eu³⁺,Y³⁺)?0?x,y?1?,Sr₅MgLa_2-x-y?BO₃?₆:xEu³⁺,yDy³⁺,Sr₅MgLa_2-x-y?BO₃?₆:xTb³⁺,ySm³⁺,Sr₅MgLa_2-x-y?BO₃?₆:xBi³⁺,ySm³⁺,Sr₅Mg_1-xLa_2-y?BO₃?₆:xMn²⁺,yCe³⁺.Among them,Sr₅MgLa_2-x-y?BO₃?₆:xBi³⁺,yM(M=Eu³⁺,Y³⁺)?0?x,y?1?emit strong blue light of Bi³⁺ion peaked at 431 nm under 340 nm light excitation,and the emission intensity reach its maximum when the doping concentration x is 0.1.When the Bi³⁺and Y³⁺were codoped into Sr₅MgLa₂?BO₃?₆ matrix,the emission intensity of Bi³⁺increased significantly,and the excitation peak occurred red shift.When Bi³⁺and Eu³⁺were codoped into Sr₅MgLa₂?BO₃?₆,the emissions peaked at 434 nm and 614 nm were showed under the excitation of 340 nm or 396 nm,which belong to the ³P₁-¹S₀ transition of Bi³⁺and ⁵D₀ to ⁷F₂ transition of Eu³⁺,respectively.The chromaticity coordinates of the Sr₅MgLa_2-x-y?BO₃?₆:xEu³⁺,yDy³⁺samples can been regulated effectively by adjusting the ratio of Dy³⁺and Eu³⁺doping concentration,Eu³⁺can been used to improve the red component in phosphor powder.In the Sr₅MgLa_2-x-y?BO₃?₆:xTb³⁺,ySm³⁺system,Tb³⁺can sensitize the luminescence of Sm³⁺,and can adjust the color from green to red light.In the Sr₅MgLa_2-x-y?BO₃?₆:xBi³⁺,ySm³⁺system,Bi³⁺has sensitization effect on the emission of Sm³⁺,and the luminescent color can be regulated.For Sr₅Mg_1-x-x La_2-y?BO₃?₆:xMn²⁺,yCe³⁺system,fixed the concentration of Ce³⁺,the emission peaked at 434 nm decreased with the increase of Mn²⁺concentration,indicating that energy transfer occurred between Ce³⁺and Mn²⁺.In the fifth chapter,the rare earth ions doped borate aluminum based phosphors Al_4-xM_xB₂O₉ and Al_18-x8-x M_xB₄O₃₃?M=Eu,Tb,Dy?have been synthesized by using high temperature solid phase method.A small amount of rare earth ions has little influence on the structure of the Al₁₈B₄O₃₃or Al₄B₂O₉ matrix,but different structures of luminescent materials can been obtained under different calcination temperatures.Al₄B₂O₉ phase can been prepared under 900?,A₁₈B₄O₃₃phase can been obtained between 1200?-1300?range,and a mixture of both emerge in the range of 1000?-1100?.In both borate aluminum matrix,the activated ions showed corresponding characteristic emission,and the luminescence intensity of the sample Al_18-xM_xB₄O₃₃was significantly lower than that of Al_4-xM_xB₂O₉?M=Eu,Tb,Dy?.