Preparation And Performance Study Of New Germanate Luminescent Material

As an environment friendly luminescent material,germanate has been widely used in indoor light,indication signs,safety emergency and architectural decoration due to its excellent physical and chemical properties,thermal stability for the luminescent center.In this paper,a series of Mg Ge O₃:(Sm³⁺,Tb³⁺,Pr³⁺,Tm³⁺),Li YGe O₄:(Tb³⁺,Eu³⁺,Tb³⁺-Eu³⁺),Na YGe O₄:Bi³⁺and Li Lu Ge O₄:Tb³⁺phosphors were successfully prepared by high temperature solid state reaction.The preparation process,crystal structure,micro-morphology,luminescence properties and thermal stability were systematically studied.1.In order to study the influence of rare earth doped Mg Ge O₃compounds on their luminescent properties,a series of Mg Ge O₃:(Sm³⁺,Tb³⁺,Pr³⁺,Tm³⁺)phosphors were successfully prepared by high temperature solid state reaction.The optimum sintering temperature and time of Mg Ge O₃:(Sm³⁺,Tb³⁺,Pr³⁺,Tm³⁺)phosphors were investigated,and the influence of different doping concentration on the luminescent properties of the samples was studied.At different doping concentrations,Mg Ge O₃:(Sm³⁺,Tb³⁺,Pr³⁺,Tm³⁺)phosphors were successfully synthesized and the XRD patterns were Rietveld refined.At the optimum doping concentration,the sample particles are plump,the surface is smooth,and the grains are well developed.Subsequently,the thermal stability of Mg Ge O₃:(Sm³⁺,Tb³⁺,Pr³⁺,Tm³⁺)phosphor doped with different rare earth ions was studied and compared.The results showed that the thermal stability of Mg Ge O₃:Sm³⁺phosphor was the best,and the luminous intensity at 400 K was 80.7%of the initial intensity.At the same time,the chromaticity coordinates and related color temperatures of the samples were analyzed in detail.Mg Ge O₃:(Sm³⁺,Pr³⁺)phosphors emits orange-red light,Mg Ge O₃:Tb³⁺phosphor emits green light and Mg Ge O₃:Tm³⁺phosphor emits blue light.In addition,the energy transfer energy level diagram of Mg Ge O₃:(Sm³⁺,Tb³⁺,Pr³⁺)phosphors was established,and the luminescence mechanism of doped rare earth ions was analyzed.2.The influence of rare earth ions(Tb³⁺,Eu³⁺)doping on the luminescent properties of Li YGe O₄:(Tb³⁺,Eu³⁺,Tb³⁺/Eu³⁺)phosphors was systematically studied.When Tb³⁺ions doped Li YGe O₄:Tb³⁺phosphor,the sample emits green light.When Eu³⁺ions doped Li YGe O₄:Eu³⁺phosphor,the sample emits red light.When Tb³⁺/Eu³⁺ions co doped Li YGe O₄:30%Tb³⁺,y Eu³⁺phosphor,the chromaticity coordinate of the sample moves from the green area to the red area through the yellow area,indicating that the phosphor can be used as a color tunable luminescent material.The influence of doping concentration on the micro-morphology and luminescent properties of Li YGe O₄:(Tb³⁺,Eu³⁺,Tb³⁺/Eu³⁺)phosphors was studied.When the ions doping concentration is 30%,the sample particles are full,the crystal grains are complete,and the luminous performance reaches the maximum.The excitation and emission spectra of Li YGe O₄:(Tb³⁺,Eu³⁺,Tb³⁺/Eu³⁺)phosphors were studied in detail.The sample can be effectively excited by near ultraviolet and blue light,and its luminescence performance is very excellent.At the same time,the thermal stability of Li YGe O₄:30%Tb³⁺phosphor excited by near ultraviolet and blue light was compared.The results show that the thermal stability of Li YGe O₄:30%Tb³⁺phosphor under blue light excitation is stronger than that under near ultraviolet excitation.Similarly,the energy transfer energy level diagram of Li YGe O₄:(Tb³⁺,Eu³⁺,Tb³⁺/Eu³⁺)phosphor was established,and the luminescence mechanism of the phosphor was analyzed.3.The Li Lu Ge O₄:Tb³⁺and Na YGe O₄:Bi³⁺phosphors were prepared and synthesized.The effects of different Tb³⁺/Bi³⁺concentrations on the crystal structure,micro-morphology,luminescent properties and afterglow properties of Li Lu Ge O₄:Tb³⁺and Na YGe O₄:Bi³⁺phosphors were studied in detail.The excitation and emission spectra of the sample show that Li Lu Ge O₄:Tb³⁺phosphor can be effectively excited to green light by near-UV and blue light,while Na YGe O₄:Bi³⁺phosphor can only be effectively excited to blue light by near-UV light.At the same time,the thermal stability and chromaticity coordinates of Li Lu Ge O₄:Tb³⁺and Na YGe O₄:Bi³⁺phosphors were studied in detail.The results show that both phosphors have excellent thermal stability and low relative color temperature,and can be used as a potential luminescent material in the field of low color temperature solid-state lighting.In addition,the electronic structure diagram（VRBE diagram）and the long afterglow luminescence mechanism diagram of Li Lu Ge O₄and Na YGe O₄were constructed through the combination of experimental data and theory,and the impurity energy level positions formed by lanthanide ions in the matrix were obtained,and the long afterglow luminescence mechanism was analyzed.