Preparation And Performance Study Of Rare Earth Doped Germanate Luminescent Material

With the continuous development and progress of society,people’s requirements for lighting systems are getting higher and higher.People hope to obtain high-efficiency lighting systems that are more environmentally friendly,energy-saving and eye-protecting,and have rich and adjustable light colors.As a photoluminescent material with a wide range of uses,phosphor powder is one of the indispensable supporting products for the recently emerging ultraviolet LED（UV-LED）lighting technology.The research of higher-level applications of rare earths is of great significance for solving the dilemma of my country’s rare earth exports and protecting the safety of my country’s rare earths.In this paper,the host material Li YGe O₄ is prepared by high-temperature solid-phase method based,and a series of new color phosphors Li YGe O₄:Tb³⁺,Li YGe O₄:Dy³⁺,Li YGe O₄:Tm³⁺are prepared by rare earth single doping,and prepared by rare earth co-doping New white phosphor Li YGe O₄:Dy³⁺,Tm³⁺.A series of phosphors Li Y_1-xGe O₄:x Tb³⁺were successfully developed by using rare earth Tb³⁺ions to replace the lattice positions of Y³⁺in the host Li YGe O₄.Under the excitation of 378nm ultraviolet light,it can produce a green light emission around550nm with stronger intensity and purer light color than commercial phosphors,which comes from the electronic energy level transition of ⁵D₄→⁷F₅ produced by Tb³⁺4f layer electrons.The luminous intensity of the phosphor increases first and then decreases with the doping concentration,and reaches the strongest when the doping concentration is30%.When doped at a lower concentration,the phosphor can also produce a long afterglow effect;the thermal stability test results show that its thermal quenching activation energy（35）（36）≈0.37e V.A new type of phosphor Li Y_1-xGe O₄:x Dy³⁺was developed by single doping of rare earth ions Dy³⁺.Under the excitation of ultraviolet light,blue light emission around485nm and yellow light emission around 577nm can be produced simultaneously.With the increase of doping concentration,the overall light color will have a changing trend from yellow light to cool white light.When the doping concentration is 5%,it can produce yellowish warm white light,and the CIE coordinates are（0.3973,0.4149）.The phosphor can still maintain 77.8%of the luminous intensity in a high temperature environment of 100°C.Doped Tm³⁺rare earth ions in the matrix Li YGe O₄,and successfully developed a series of new phosphors Li Y_1-xGe O₄:x Tm³⁺.Under the irradiation of 354nm ultraviolet light,the luminescent center Tm³⁺can obtain a large amount of energy transferred by the matrix,resulting in an electronic energy level transition of ¹D₂→³F₄,which is manifested as a sharp blue light emission around 456nm.When the Tm³⁺doping concentration is 0.5%,the overall luminous intensity of the material is the strongest,further increasing the doping concentration will lead to concentration quenching due to the energy transfer interaction between the nearest neighbor ions.The color purity analysis shows that the best color purity of the phosphor can reach 98.1%.A new type of single-matrix white light phosphor Li Y_0.99-xGe O₄:1%Dy³⁺,x Tm³⁺was successfully developed by co-doping rare earth ions Dy³⁺and Tm³⁺.Under the excitation of ultraviolet light,the yellow light generated by the ⁴F_9/2→⁶H_13/2 electronic energy level transition of Dy³⁺is mixed with the blue light generated by Tm³⁺,initially forming white light emission.The experiment fixed the doping concentration of Dy³⁺at1%molar ratio,and adjusted the doping concentration of Tm³⁺from 0.05%to 5%,the light color changed from warm white light to light blue light.Experiments show that351nm ultraviolet light excitation and 1%Dy³⁺,0.5%Tm³⁺doping ratio are the best white light generation conditions.At this time,the CIE coordinates are（0.3270,0.3273）,which is very close to the CIE coordinates（0.33,0.33）of standard white light.In the thermal stability analysis,it is concluded that the smaller the activation energy calculated by applying the Arrhenius equation to the phosphor,the better.The test shows that at 150°C,its luminous intensity remains 72.1%of the initial intensity,and the thermal quenching activation The energy（35）（36）is about 0.134e V.