Preparation And Luminescence Properties Of Rare-earth Doped M-Si-Al-N Materials

In recent years,white light-emitting diodes?WLED?is known as the fourth generation light source,with energy saving,environmental protection,long life,low power consumption,high brightness and so on.Phosphors is an important part of the phosphor converted white LED,which are used in combination with blue or near ultraviolet LED chip to produce white light.The quality of the phosphors directly determines the performance of white LED,such as color rendering index,color temperature and luminous efficiency etc.Nitride phosphors have attracted much attention of researchers because of its excellent luminescent properties.At present,the performance of most of the nitride phosphors needs to be further improved,and the types of nitride red fluorescent materials are too small and the related mechanism research is incomplete.Therefore,in this paper,the research work is carried out from the following four aspects:1.?1?Pure nitride Ca-a-sialon orange phosphors with the composition Ca1.4-xAl2.8Si9.2N16:x Eu²⁺(CASN:x Eu²⁺,x = 0–0.3)were successfully prepared by gas-pressed sintering using metal nitride as raw materials.Compared with the oxygen containing Ca-a-sialon:Eu²⁺ and commercial YAG:Ce³⁺ phosphors?P46-Y3?,CASN:x Eu²⁺ exhibit a longer wavelength emission and better thermal stability.The results indicate that CASN:x Eu²⁺ is a promising yellow phosphor for white LED.?2?The Photoluminescence and cathodoluminescence properties of Ce³⁺ doped CASN were investigated.The luminescent properties of the phosphors were controlled by changing the Ce³⁺ concentration and the composition of the matrix.Under the excitation of 395 nm,the emission peak of CASN: x Ce³⁺ is located at 525 nm,and the FWHM is 135 nm.At 150?,the emission intensity of the sample was reduced by only 13%.Under the excitation of electron beam,the sample CASN: x Ce³⁺ has good resistance to current saturation and excellent resistance to degradation and good color stability.?3?The structure and luminescent properties of the CASN:Eu²⁺ phosphors were modify by cation substitution(Al³⁺?Si4+).And the mechanisms of the red-shift of emission and the improvement of the emission intensity and thermal quenching have been explored.Owing to the increase of the crystallinity with Al³⁺ introducing,the emission intensity of the phosphors increases.The modified structure results in a strong covalence of Eu-N and an improvement of the thermal quenching.2.?1?Eu²⁺ doped and Eu²⁺,Ce³⁺ co-doped Li Si₂N₃ phosphors were successfully prepared by gas-pressed sintering.The dominant excitation band of Li Si₂N₃:Eu²⁺ was found at about 355 nm and exhibited a broad-band yellow emission centered at 592 nm instead of the early reports of 310 nm and 580 nm,respectively.The shifting behavior dominantly contributed to different oxygen content in the host.The detailed energy transfer mechanism from Ce³⁺ to Eu²⁺ in the Li Si₂N₃ host was also explored.?2?The effects of a solid solution of Al N on the crystal structure,morphology,thermal quenching and photoluminescence properties of Li Si₂N₃:Eu²⁺ phosphor were studied.The luminescence intensity of Li Si₂N₃:Eu phosphor is significantly improved by the solution of Al N,but the emission position is unchanged.The results show that these solid solutions could be the most useful way to improve the luminescence intensity of phosphors.3.Eu²⁺/Ce³⁺ doped Ca3Li4-ySi2N6-yOy?0?y?1.5??CLSN?were successfully prepared by conventional solid-state reaction and their luminescence properties and electronic structure were studied.The undoped CLSN shows red defect-related luminescence,Eu²⁺ and Ce³⁺ doped CLSN also show red emission centered at 702 nm and 673 nm,respectively.The thermal stability of CLSN is also investigated.The results indicate that CLSN:Eu²⁺/Ce³⁺ could be conducive to the development of phosphor-converted light-emitting diodes.4.A series of Li Ca Al N₂:Eu³⁺/Tb³⁺ phosphors were successfully prepared by solid-state reaction.The photoluminescence?PL?properties of Li Ca Al N₂:Eu³⁺/Tb³⁺ and the cathodoluminescence?CL?properties of Li Ca Al N₂:Tb³⁺ were investigated in detail The Eu³⁺(Tb³⁺)doped Li Ca Al N₂ shows red?green?emission peaking at 615 nm?550 nm?.Monitored at 615 nm?550 nm?,it is interesting to found that Li Ca Al N₂:Eu³⁺(Li Ca Al N₂:Tb³⁺)has a broad charge transfer band ranging from 350-450 nm?275-375 nm?.Li Ca Al N₂:Tb³⁺ exhibits a good resistance to the current saturation.The white LED has also been fabricated with blue,green,and Li Ca Al N₂:Eu³⁺ red phosphor.The results indicate that Li Ca Al N₂:Eu³⁺/Tb³⁺ could be conducive to the development of phosphor-converted LEDs and FEDs.