Ba^(2+)替代对Sr_4Al_(14)O_(25):Eu^(2+),Dy^(3+)结构和发光性能的影响

Structure and Luminescence Properties of Sr_4Al_(14)O_(25):Eu^(2+),Dy^(3+) by Ba^(2+) Substitution

采用高温固相反应按化学式Sr4-xBaxAl14O25:Eu2+,Dy3+(x=0,0.8,1.6,2.4,3.2,4)配比原料,合成长余辉发光材料。X射线衍射分析表明,当x=0.8时,产物物相为单斜结构SrAl2O4和磁铅矿结构SrAl12O19共存;当x>1.6时,产物主相转变为BaAl2O4六角结构。对所得样品采用360nm光照,发射光谱表明,样品发光是以Eu2+为发光中心,由Eu2+电子4f65d-4f7跃迁所致,并且随着Ba掺入量的增加,样品发射光谱峰位产生移动,这是由于Sr2+取代产物中Ba2+位置后,导致晶格收缩,影响Eu2+的5d能级劈裂,从而影响电子4f65d-4f7跃迁。余辉光谱显示x>1.6时,产物的余辉发光是以BaAl2O4基质中Eu2+为发光中心。余辉衰减检测和热释光谱分析发现不同掺Ba量的样品余辉衰减快慢不同,是由于其中存在的陷阱能级深度不同,且陷阱能级越深,其余辉时间越长。

The rare-earth doped strontium aluminate phosphors Sr4-xBaxAl14O25：Eu2＋,Dy3＋（x=0,0.8,1.6,2.4,3.2,4） were synthesized by a high temperature solid-state reaction method.The phase structures of the phosphors were characterized by X-ray diffraction.The results show that the monoclinic SrAl2O4 and hexagonal SrAl12O19 co-exist in the sample with x=0.8.The major phase of phosphors is hexagonal BaAl2O4 when x1.6.It is indicated that the phase structure of the samples changes from Sr4Al14O25 to BaAl2O4 when the value of x changes from 0 to 4.The emission spectra of 360 nm irradiation reveal that Eu2＋ is the luminescence center of the samples due to 4f65d-4f7 transition of Eu2＋ electron.With the Ba doping content increasing,the shift of emission spectra peak occurs,because the lattice shrinkage caused by Sr2＋ substitution for Ba2＋ affects the 5d level cleavage of Eu2＋ and thus influences the 4f65d-4f7 transition.The afterglow spectra show that Eu2＋ of BaAl2O4 is the luminescence center for the products when x1.6.The decay characteristics show that the phosphor samples with different Ba2＋ content have different afterglow time,and the afterglow time also changes with the value of x.The measurement of thermoluminescence reveals that the trap depth of the phosphor samples with different Ba2＋ content is different,and the samples with deeper traps have longer afterglow time.