Preparation And Luminescence Properties Of Two Oxide Phosphors Research

Light-emitting diode（abbreviated as LED）has the advantages of high luminous efficiency,environmental protection,low energy loss,and long service life.With the development of phosphor-converted light-emitting diode（Phosphor converted light-emitting diode abbreviated as pc-LED）technology,pc-LED can be applied in various aspects such as green solid-state lighting,display,plant lighting,and biomedical.In the field of solid-state lighting,commercial white LEDs are made by mixing blue LED chips and yellow phosphor YAG:Ce³⁺.Due to the lack of red light-emitting components in the YAG:Ce³⁺phosphor luminescence spectrum,the luminescence is biased toward cold white light,which is not conducive to people’s eye health.This white light LED because of the lack of color also has the disadvantage of a low color rendering index.In plant lighting and biomedicine,the main research direction is in the field of deep infrared and near-infrared phosphors.However,the overall performance of NIR phosphors studied so far is not enough to meet people’s needs,such as poor thermal stability and low photoelectric conversion efficiency.With the progress of social development and people’s requirements for various extreme environments,the performance requirements of pc-LED are getting higher and higher.The phosphor,as an important part of pc-LED,greatly affects the luminous performance of pc-LED.This requires the development of phosphors with better performance,thermal stability,and luminous efficiency.In this paper,two oxide-based phosphors are studied and their luminescence properties,thermal stability,luminescence efficiency,and other performance are analyzed as follows:（1）Luminescence properties of multicolor emitting La₄GeO₈:Tb³⁺,Eu³⁺phosphors.La₄GeO₈:Tb³⁺,Eu³⁺phosphors were prepared by solid-phase reaction method.The photoluminescence properties of La₄GeO₈:Tb³⁺,Eu³⁺were systematically investigated.The energy transfer in the Tb³⁺-Eu³⁺-doped La₄GeO₈phosphor is the result of quadrupole-quadrupole interactions.The thermal stability of the La₄GeO₈:0.07Tb³⁺,0.01Eu³⁺phosphor was demonstrated using variable temperature emission spectra from 303 K to 513 K.The activation energies of Tb³⁺and Eu³⁺ions obtained from the fitting calculations were 0.186 e V and 0.187 e V,respectively.By varying the Eu³⁺to Tb³⁺content ratio,the samples could achieve multicolor luminescence and tunable colors from green to red under 265 nm light excitation.These results indicate that La₄GeO₈:Tb³⁺,Eu³⁺is a promising solid-state luminescent material.（2）Broadband near-infrared luminescent properties of Cr³⁺activated SrGa₂Si₂O₈phosphor.A series of SrGa₂Si₂O₈:Cr³⁺phosphors with near-infrared emission were prepared by a solid-phase reaction method.They exhibit strong broadband emission in the 600-950 nm region corresponding to the spin-allowed ⁴T₂→⁴A₂jump.The phosphor emission intensity peaks at a doping concentration of 0.005.The emission of SrGa₂Si₂O₈:Cr³⁺phosphor in the octahedral lattice is caused by the[Ga O₄]tetrahedral to[Cr O₆]octahedral distortion due to the doping of Cr³⁺ions.The energy transfer interaction between the trivalent Cr ions is a dipole-dipole interaction.The total emission intensity of SrGa₂Si₂O₈:Cr³⁺phosphor can be maintained at 83.42%at 420 K compared to300 K,indicating its high thermally stable luminescence.The calculated internal quantum efficiency of SrGa₂Si₂O₈:Cr³⁺phosphor is 23.6%.The NIR output power of the LED device is 53m W when the driving current is 20 m A,and the photoelectric conversion efficiency is 2.25%.We can all see the blood vessels inside the palm of the human finger obviously under the near-red camera shot.It shows that SrGa₂Si₂O₈:Cr³⁺near-infrared pc-LED has some application value in biomedical applications.