Synthesis And Application Of Eu³⁺ Doped Yttrium Tungstate

LED（light emitting diode）is a semiconductor device that takes light-emitting diode as the core to convert electric energy into light energy.It can directly convert electricity into light.As LED has many advantages such as long service life,low power consumption and environmental protection,it will gradually replace incandescent lamp and fluorescent lamp in the future.Light conversion coating method is the mainstream technical scheme to obtain white LED at present.As one of the key materials of LED packaging,the performance of phosphor directly affects the overall quality of LED products.Tungstate phosphors have attracted extensive attention in the industry because of their stable performance and high luminous efficiency.In this paper,a variety of tungstate red phosphors were prepared by changing the Y/W ratio by high temperature solid state method,and their properties were studied.The main contents and research results are as follows:（1）Y₂W₃O₁₂:Eu³⁺and Y₂WO₆:Eu³⁺system red phosphors were newly synthesized.The experimental results show that both Y₂W₃O₁₂:Eu³⁺and Y₂WO₆:Eu³⁺system red phosphors can be used by near-ultraviolet LED chips and blue LED chips.The emission peak is located near613 nm(⁵D₀→⁷F₂transition of Eu³⁺ions);and under the excitation wavelength of 396 nm,the luminous intensity of the Y₂WO₆:Eu³⁺red phosphor is significantly better than that of the Y₂W₃O₁₂:Eu³⁺red phosphor,Its relative luminous intensity is 2.1 times that of the Y₂W₃O₁₂:Eu³⁺red phosphor,indicating that the phosphor of this system can be used in the manufacture of white LEDs with three-primary phosphor systems or as red compensation powders for"blue LED+yellow phosphor systems".（2）The red phosphor Y_2-xWO₆:Eu_x³⁺（x=0.02,0.06,0.10,0.14,0.18）was successfully synthesized by high temperature solid state method.This series of phosphors can be effectively excited by near ultraviolet light（396 nm）and blue light（466 nm）and emit red light with the main peak at 616 nm.The experimental results show that the luminous intensity of red phosphor Y_2-xWO₆:Eu_x³⁺（x=0.02,0.06,0.10,0.14,0.18）reaches the maximum when x=0.1,and when x>0.1,the concentration quenching of Eu³⁺occurs in Y₂WO₆:Eu³⁺red phosphor.The concentration quenching of Eu³⁺is caused by multistage interaction,and the type of multistage interaction is electric dipole electric dipole interaction.All experimental results show that this series of phosphors is very suitable for the manufacture of white LED.（3）Eu³⁺-Bi³⁺,Eu³⁺-Ga³⁺,Eu³⁺-Sm³⁺Co doped yttrium tungstate（Y₂WO₆）system red phosphors were prepared by high temperature solid state method.The experiments show that this series of phosphors can be effectively excited by near ultraviolet light（396 nm）and blue light（466 nm）,and the main emission peak is located in the red region at 613 nm.In the red phosphor of Y₂WO₆:Eu³⁺,Bi³⁺system,there is sensitization between Eu³⁺-Bi³⁺,and the co doping of Eu³⁺-Bi³⁺increases the relative brightness of the sample by 28%.Appropriate doping of Bi³⁺will not only increase the intensity of the excitation peak at 466 nm,but also increase the width of the excitation peak,which is more conducive to the packaging of white LED devices.The optimum doping concentration of Bi³⁺is 0.01 mol.In the red phosphor of Y₂WO₆:Eu³⁺,Ga³⁺system,a large energy transfer occurs between Ga³⁺and Eu³⁺,and the relative brightness of the sample is increased by 49%due to the co doping of Eu³⁺-Ga³⁺.The optimum doping concentration of Ga³⁺is 0.01 mol,and the color coordinates of Y_1.89WO₆:Eu³⁺_0.1,Ga³⁺_0.01are（0.6658,0.3340）,It’s better than the color coordinate of Y_1.89WO₆:Eu³⁺_0.1,Ga³⁺_0.01（0.6618,0.3379）,which is closer to the NTSC standard value（x=0.670,y=0.330）.In the red phosphor of Y₂WO₆:Eu³⁺,Sm³⁺system,Sm³⁺sensitizes Eu³⁺and the Eu³⁺-Sm³⁺CO doping increases the relative brightness of the sample by 85%.Appropriate Sm³⁺doping will not only improve the strength of transfer band CBT,but also increase the width of excitation peak,which is more conducive to the packaging of white LED devices.The optimum doping concentration of Sm³⁺is 0.01mol.（4）The prepared phosphors of Y₂WO₆:Eu³⁺,Bi³⁺,Y₂WO₆:Eu³⁺,Ga³⁺,Y₂WO₆:Eu³⁺,Sm³⁺can be used as red light compensation powder of"blue LED+yellow phosphor system"to improve the color rendering index of white LED.