Synthesis And Characterization Of Borate Phosphors For LED

Borate has the advantages of mild synthesis conditions,diversified structure,and good structural rigidity.Therefore,the borates are suitable as the matrix for phosphors.The correlation between the composition,morphology,luminescence efficiency and thermal stability of the phosphors used in LEDs has always been the focus of this research field.Focusing on these related scientific issues,we have separately studied the preparation and luminescence properties of blue phosphors and yellow phosphors with high quantum yields and single-phase white phosphors.The specific innovations are as follows:1.Prepared the blue phosphor Sr_0.98Ga₂B₂O₇:0.01Bi³⁺,0.01Dy³⁺with high quantum yield.Bi³⁺doping in SrGa2B2O7 can obtain phosphors with stable blue emission,and co-doping Dy³⁺as sensitizer can enhance the emission intensity of Bi³⁺,a blue phosphor with higher luminescence efficiency can be obtained.Among them,Sr_0.98Ga₂B₂O₇:0.01Bi³⁺,0.01Dy³⁺blue phosphor has a quantum yield of 65.5%,a half-peak width of about 65 nm and a color purity of 94%.Moreover,Sr0.98Ga2B2O7:0.01Bi³⁺,0.01Dy³⁺blue phosphor has good thermal stability,and maintains a high emission intensity in the temperature range from room temperature to 100?. specially in the temperature range from room temperature to 75°C,the emission intensity will increase as the temperature rises,and then in the temperature range of75?100?,the emission intensity decreases as the temperature rises.When the emperature reaches 100?,the emission intensity decreases to the intensity at room temperature.2.Doping Dy³⁺in SrGa2B2O7 can obtain yellow phosphor,and co-doping with Si⁴⁺or Al³⁺can enhance the emission intensity of Dy3+.Among them,the quantum yield of Sr0.95Ga2B2O7:0.05Dy³⁺yellow phosphor is 3.9%,and the quantum yield of Sr_0.95Ga_1.6B₂O₇:0.05Dy³⁺,0.4Si⁴⁺yellow phosphor is increased to 33.3%.In addition,by doping Dy³⁺,Si⁴⁺and Bi³⁺in SrGa₂B₂O₇ at the same time,the single-phase white phosphors can be obtained,which have good white emission under near-ultraviolet ight excitation,and precise adjustment of luminescence color can be achieved by djusting the ratio of Si⁴⁺.The precise adjustment of white light,when the ratio of Si⁴⁺is 0.18,the color coordinates are(0.333,0.333),which is particularly close to the tandard equal energy white light.The emission intensity of Sr0.95Ga1.6B2O7:0.05Dy³⁺,0.4Si⁴⁺yellow phosphor at 200?is 87.4%of room temperature intensity,the mission intensity of Sr_0.94Ga_1.82B₂O₇:0.05Dy³⁺,0.18Si⁴⁺,0.01Bi³⁺white phosphor at200°C is 96.9%of the room temperature intensity,and both exhibit excellent thermal stability.3.By co-doping Bi³⁺-Tb³⁺-Eu³⁺and Bi³⁺-Tb³⁺-Sm³⁺in the Gd₂MoB₂O₉ matrix,the white phosphors that are very close to the standard is obtained.In the Gd2MoB2O9matrix,Bi³⁺can emit blue light and effectively transfer energy to rare earth ions, hereby obtaining phosphors with adjustable luminescence colors.Under the xcitation of 280 nm ultraviolet light,the color coordinates of Gd1.474MoB2O9:0.3Bi³⁺,0.2Tb³⁺,0.026Eu³⁺and Gd_1.46MoB₂O₉:0.3Bi³⁺,0.19Tb³⁺,0.05Sm³⁺white phosphors are(0.339,0.335)and(0.332,0.346),very close to the standard equal energy white ight.In addition,the thermal stability of the white phosphors is good.From room temperature to 200?,the luminescence color remains in the white region,and the half-decay quenching temperature T1/2 is 513.33 K and 655.15 K,respectively.d_2-x-y-zMoB₂O₉:xBi³⁺,yTb³⁺,zEu³⁺/Sm³⁺white phosphors are synthesized in air atmosphere,have high chemical stability and good practical prospects.4.Doping Tb³⁺in LaMoBO6 to obtain a green phosphor that can be excited by ultraviolet light and blue light,and it has a high quantum yield when excited by blue light.Co-doping Tb³⁺and Eu³⁺/Sm³⁺can obtain yellow phosphor excited by ltraviolet and blue light.Tb³⁺can effectively transfer energy to Eu³⁺or Sm³⁺.In addition,co-doping Bi³⁺can increase the luminescence intensity of the yellow hosphors.The quantum yield of La_0.575MoBO₆:0.4Tb³⁺,0.005Eu³⁺,0.02Bi³⁺yellow phosphor under 487 nm blue light excitation reaches 92%.It has good practical value in the white light source.5.Doping Bi³⁺in the non-rare-earth matrix MGa2B2O7(M=Sr,Ba)can obtain the phosphors with stable blue emission,while co-doping with Al³⁺can enhance the emission intensity of Bi³⁺and obtain blue phosphors with very high quantum yields.The quantum yield of Sr_0.99Ga_1.50B₂O₇:0.01Bi³⁺,0.50Al³⁺blue phosphor is 96%,and the quantum yield of Ba_0.995Ga_1.60B₂O₇:0.005Bi³⁺,0.40Al³⁺blue phosphor is as high as 99%.The study found that the phosphors in which Ga³⁺is replaced by Al³⁺will oduce a spinodal-like phase separation structure.Moreover,the Debye characteristic temperature of the phosphors can be increased,reducing the energy loss caused by the non-radiative transition of the phosphors,thereby improving the emission intensity nd quantum yield of the phosphors.In addition,Sr0.99Ga2B2O7:0.01Bi³⁺and r_0.99Ga_1.50B₂O₇:0.01Bi³⁺,0.50Al³⁺blue phosphors have intrinsic negative thermal quenching properties,and the emission intensity increases with the temperature rises.There will be no thermal quenching in the range of room temperature to 200?.Moreover,the structure of the phosphors will not undergo phase change or other changes with the temperature rises,and the thermal stability is high.