Ce3+和Tb3+, Eu3+在六方NaLnF4(Ln=La,Gd或Y)中的发光和能量传递

本文报道Ce3+掺杂和Ce3+—Tb3+、Ce3+—Eu3+共掺杂的六方NaLnF4(Ln=La,Gd或Y)发光体的研究结果:氟配位环境使Ce3+在300nm附近发射并有很低的猝灭浓度;阳离子缺陷发光中心可能形成于NaGdF4基质中并被Ce3+—Gd3+共同敏化;Ce3+的发光可以因Tb3+掺杂而增强,反过来Ce3+亦会使Tb3+的5D3/5D4发射强度比减小;Ce3+含量增加使Eu3+的5D2/5D1及5D2/5D0发射强度比减小,这与Ce3+的2F5/2→2F7/2跃迁和Eu3+的5D2→D1跃迁能级差匹配而产生共振能量传递有关。

THE LUMINESCNECE AND ENERGY TRANSFER OF Ce3+, Tb3+ AND Eu3+ IN HEXAGONAL-NaLnF4 (Ln=La,Gd or Y)

For the advanced study of the luminescence of Ce3+ in various coordination environment served as are activater or sensitizer, the luminescence and energy transfer phenomena in hexagonal-NaLnF4 (Ln=La Gd or Y) doped with Ce3+, Ce3+-Tb3+, Ce3+-Eu3+ have been investigated and some results are reported in this paper.The same luminescence centre of Ce3+ formed in NaLaF4 and NaYF4 and the higher energy transfer efficiency of that in the host lattices are suggested from the fact that in the two host lattices Ce3+ emits near 300nm with the close luminescence intensity and that the quenching concentration is very low for Ce3+ in the flouride.A broad band with a max. emission peak at 420nm was observed in the host lattice of NaGdF4 and the doped NaGdF4:Ce3+ under the excitation of 273.5nm (Gd3+ 6p-8S) and 250nm (only for NaGdF4 at 77K and room temperature). Comparing the excitation and the emission spectra of NaGdF4 and NaGdF4:Ce3+, the relationship between the concentration of Ce3+ and the luminescence intensity of the broad band and Gd3+ in NaGd1-xCexF4 (x=0, 2.5, 3.5, 1) and the results-reported in some referencesthat the cation-defect centre or electron-self-trcped hole centre could be observed in some flou-rids especially containing Gd3+ which could provide a shallow trap for electron, we suggest that one kind of cation-defect centre may exist in the NaGdF4 host lattice (broad band emit in 420nm) and be sensitized by Ce3+ and Gd3+ through the pathway from (Ce3+→Gd3+) to cation-defect centre.