Synthesis And Luminescent Properties Of Rare-earth Doped Molybdates

The LED production is nowadays rapidly developing.For the lighting field,scientists are exploring luminescent materials with excellent luminescent materials constantly.As one of the most important components of the mainstream LED structure,PC LED,the luminescence properties of the phosphors have an important impact on LED lighting indicators.With the largest share of the rare-earth resources in the world,China should pay more attention to the in-depth study on the luminescent rare-earth resources.The rare-earth doped molybdates have a stable structure,and it can absorb ultraviolent light effectively,which can broaden the selection rage of rare-earth luminescent materials and moreover,promise the expending of the application,such as the area of the lighting,display,detection,imagining and other emerging technologies.The is application environment is broadening,and the LED chip technology continuous developing.Phosphors have a large impact on color rending,luminous efficacy and color temperature of LED.Limited by the luminescence property,the type of the phosphor may decide the performance of application,especially on the far-field illumination and high-power illumination devices.In response to the situations,the contents and results were as follows:1.LiEu（MoO₄）₂:Nd,the NIR phosphor,was synthesized by the high temperature solid reaction method.The influence of doping concentration to the luminescence intensity was explored and the best doping concentration of Nd is determined.After that,LiEu（MoO₄）₂:Nd@SiO₂with better luminescence performance was prepared through Stober method,which also efficiently improved the thermal stability of phosphor.It shows that the best doping concentration of Nd is10%,and it has a good effect of the coated sample on the luminescence intensity and thermal stability.This is has a certain significance for the further expansion of the NIR LED application field excited by blue chip.2.LiY（MoO₄）₂:Er,Yb,the phosphor with the UC emission was synthesized,and its UC mechanism is explored.The FIR and sensitivities were calculated and analyzed.SiO₂was coated on the surface of LiY（MoO₄）₂:Er,Yb,and its influence on material properties is analysis through structural characterization and spectra measurement.It shows that the phosphor has a good thermal stability and FIR under excitation of 980nm.After coated with SiO₂,the saturation threshold is raised.The LiY（MoO₄）₂:Er,Yb@SiO₂phosphor can be well applied for optical thermometry.3.Two kinds of red phosphors,LiY（MoO₄）₂:Eu and NaY（MoO₄）₂:Eu,were synthesized through high temperature solid reaction method.The luminescence properties of Eu³⁺which can emit red light in different based matrix were compared.The experimental results show that the luminescence intensity of LiY（MoO₄）₂:Eu phosphor is higher than that of NaY（MoO₄）₂:Eu.The reasons for this phenomenon may be explained as follows:（1）the crystal volume of LiY（MoO₄）₂is smaller than that of NaY（MoO₄）₂:Eu,which promotes the energy transfer between matrix and activating agent,Eu³⁺;（2）the LiCO₃in LiY（MoO₄）₂:Eu raw material provides a good reaction environment for crystal growth,so that the lattice defects can be reduced,and the luminescence intensity can be improved while the raw material forming into a new material.The experimental results provide a new routine for the improvement of luminescence intensity of red phosphors.