Luminescence Properties And Research Of Rare Earth-doped Phosphor Down-conversion&Up-conversion

Rare earth,as an important resource,was used in various fields in the world.Among them,rare earth is prepared as a phosphor light-emitting material due to its abundant energy levels,which is widely used in the field of solid light emission and display.For example,indicators,display boards,LEDs(light-emitting diodes),signal indicators,instrumentation displays and so on.Among them,the most widespread is the application of White-LEDs.As a new generation of light emitting energy,White-LEDs have received widespread attention due to their low energy consumption and high efficiency.C urrently,one of the commercially available methods for white LED synthesis is to excite the three primary color phosphors through ultraviolet or near-ultraviolet chips.By adjusting the proportion of the phosphors in each color,doping can achieve the purpose of generating white light.The advantage is that it can well adjust the color temperature of white light to achieve a good saturation.The second method is to coat the YAG:Ce3+phosphor on the blue light chip to get white light.The advantage of this method is that the cost is reduced,b ut the red saturation is slightly missing.Secondly,unlike the short-wavelength excitation phosphor for get the visible light,method of ultraviolet blue excitation phosphor,the phosphor can also generate visible light by long-wavelength excitation phosp hor for get the short-wavelength.This process is called up-conversion luminescence.Upconversion luminescence is widely used in temperature sensors and biological imaging due to its unique luminescence mechanism.In this paper,a conventional high-temperature solid-phase method was used to prepare phosphor luminescent materials of two systems,niobate and tungstate,and their luminescent characteristics were studied for different luminescent mechanisms.(1)Sr₂La_1-xNbO₆:xEu³⁺(x=0.01?0.04?0.07?0.1?0.13?0.16)red phosphor was prepared by high-temperature solid-phase method,which was tested by XRD,XPS,excitation and emission spectrum,variable temperature quantum efficiency,etc..The sample emits orange-red light under the illumination of 394nm excitation light.The peak of the emitted light is located at 612nm,which is derived from the transition of the ⁵D₀?⁷F₂ energy level.Among them,the test of Eu³⁺doped samples with different concentrations found that when the doping reached The emission inte nsity reaches the maximum value at 0.13mol%.Under the test of variable temperature emission spectrum,the sample can maintain an emission intensity of 60.7%relative to normal temperature at 423K,and then the quantum efficiency of the sample is further changed Test,the internal quantum efficiency of this sample at 423K is about 21.7%.After mixing the Sr₂La_0.87NbO₆:0.13Eu³⁺sample with a commercial green phosphor,and encapsulating the mixture with a 395nm blue LED chip,the white LED with a color rendering index of 72.9 was obtained after power-on.(2)Sr₂La_1-yNbO₆:ySm³⁺(y=0.01?0.04?0.07?0.1?0.13)red phosphor was prepared by high temperature solid-phase method,and tested by XRD,XPS,excitation and emission spectroscopy,variable temperature quantum efficiency and so on.The sample emits orange-red light under the irradiation of 405nm excitation light.The peak of the emitted light is located at 608nm,which originates from the transition of the ⁴G_5/2?⁶H_7/2 energy level.Among them,it was found through the test of samples with different concentrations of Sm³⁺doping When the doping reaches0.07mol%,the emission intensity reaches the maximum value.Under the test of variable temperature emission spectrum,the sample can maintain an emission intensity of 80.7%relative to the normal temperature at 423K,and then the temperature of the sample is further changed.For the quantum efficiency test,the internal quantum efficiency of this sample at 423K is about 2.0%.(3)Bi_1.2La_0.8-xWO₆:xEr³⁺(x=0.01?0.04?0.07?0.1?0.13)up-converted luminescent fluorescent material was prepared by high temperature solid phase method The emission peak showed strong green light at 550nm,and it was found that the sample reached its maximum value when the doping concentration was 0.1.And by using Yb³⁺ion as a sensitizer doping,Bi_1.2La_0.7WO₆:0.1Er³⁺/0.03Yb³⁺phosphor was obtained.Due to the energy transfer effect from Yb³⁺to Er³⁺,its emission intensity was further improved.It shows that the sample can be used as a heat detector,biological imaging and so on.(4)The up-conversion fluorescent material of Er³⁺ion-doped Y₂WO₆ sample was synthesized by high-temperature solid-phase method,and its performance was tested and studied using diffuse reflection,XRD,emissio n spectrum,etc.Among them,the sample was found to be There is an obvious absorption peak near 970nm,and using the formula of diffuse reflection and band gap calculation,the direct band gap of the matrix should be 4.36e V.After exciting the sample with a 976nm laser,a green emission light was obtained with a peak of 545nm.After doping with different concentrations of Er³⁺,it was found that the luminous intensity of this series of samples reached a peak when the doping concentration was 0.09mol%,whic h occurred The concentration is quenched.Further,by fitting the emission intensity after excitation of samples with different pump power lasers,it is concluded that the up-conversion should be the mechanism process of two-photon excitation.