Study Of Luminescence Properties Of Calcium And Magnesium Silicate Phosphors（CaMgSiO₄/Ca₂MgSi₂O₇）Based On Rare Earth Ions Sm³⁺,Eu³⁺ Doping And Their White Light LED Applications

With the development of society,people’s demand for light sources is getting higher and higher.From 1879 Edison invented the incandescent lamp until2014 people finally looked for a new green new light source,that is white LED（light-emitting diodes）.White LEDs are widely used in various lighting fields,such as daily lighting,agricultural farming and LCD displays.Currently,commercially prepared white LEDs are mainly used to excite yellow YAG:Ce³⁺phosphors by blue LED chips to achieve white light emission.However,the white LED devices integrated by this method lack the red part of the spectrum,resulting in poor color rendering index and high color temperature defects.Therefore,it is necessary to prepare high-performance red phosphors in order to improve the defects of conventional white LEDs that lack red light.In this paper,the preparation,photoluminescence properties,energy transfer mechanism,and application on white LEDs of new red silicate luminescent materials doped with rare-earth ions Sm³⁺,Eu³⁺have been investigated based on the extensive literature review and previous work of the group.Two series of new phosphor samples:Ca Mg Si O₄:x%Sm³⁺,y%Li⁺,and Ca₂Mg Si₂O₇:x%Sm³⁺,y%Eu³⁺were successfully synthesized by high-temperature solid-phase method.The effects of particle morphology,crystal structure,steady/transient spectra,thermal stability,charge compensator,and energy transfer on the luminescence properties of the phosphors were investigated in detail.The specific studies and results are as follows.（1）The results of the physical phase analysis showed that the prepared samples were pure phases and the doping of Sm³⁺and Li⁺had almost no effect on the crystal structure of the phosphors.The intensity of the Ca Mg Si O₄:x%Sm³⁺phosphants has increased 2.3 times and the increase of the doping concentration has increased from25 percent to 85%.The color coordinates of the phosphor are in the red region（0.605,0.394）and the color purity is as high as 93.3%.When the temperature was increased to 150°C,the peak intensity of the emission peak was maintained at 73.5%of the room temperature,which indicates that the phosphor has good thermal stability.（2）The new red phosphors with Sm³⁺,Eu³⁺co-doped with Ca₂Mg Si₂O₇ were prepared by a high-temperature solid-phase method.The findings indicate that the incorporation of Sm³⁺and Eu³⁺did in no way change the crystal structure of magnesite pyrite feldspar.The emissions intensity of Sm³⁺gradually decreased with the increase of Eu³⁺concentration.In addition,the fluorescence lifetime of Sm³⁺also reduced gradually with the enhancement of Eu³⁺concentration.These phenomena identified the existence of resonant nonradiative energy transfer from Sm³⁺to Eu³⁺in the sample with an energy transfer efficiency of 44%.The color purity was 89.3%,and the thermal stability was 87.8%of room temperature.Finally,a near-UV warm white LED（CCT～5553 K,R_a～84.8）was fabricated using the efficient red phosphor Ca₂Mg Si₂O₇:2%Sm³⁺,7%Eu³⁺along with commercial phosphors.This magnesia yellow feldspar silicate phosphor was confirmed to be expected to be feasible as a trichromatic phosphor and as a red fraction in solid-state lighting.