【摘要】 采用高温固相法,先在空气气氛下制备了SrAl2O4:Eu,Dy,后对其进行还原→氧化→还原处理。X射线衍射结果表明,经过还原→氧化→还原处理后样品的晶体结构没有改变。样品的发射光谱测试表明,在高温空气气氛下有少量的Eu3+还原成Eu2+。Eu3+和Eu2+有不同的发光特性,Eu3+产生的是线状特征光谱,发射峰值在592,616nm。Eu2+产生的是带状光谱,带的中心位置在513nm。经过还原处理的样品和经过氧化处理的样品相比,Eu2+的浓度得到显著提高,而Eu3+的浓度则急剧下降。对Eu2+的氧化、Eu3+的还原的机理进行了细致地讨论。另外,样品的热释光谱测试表明,经过氧化气氛处理和经过还原气氛处理过的样品的热释光峰值有很大的变化,但陷阱能级深度基本不变,在0.65eV左右。这表明,对长余辉材料SrAl2O4:Eu,Dy进行还原→氧化→还原处理,Eu离子价态和发光强度会产生变化,并不影响其中Dy离子的陷阱能级。更多还原

【Abstract】 As novel functional materials,long afterglow phosphors have drawn more and more attention in recent years because of a constantly growing market for their applications in traffic signs,emergency signage,watches and clocks,textile printing,among others.Amid the newly developed long afterglow materials which have already found commercial use,green-emitting SrAl2O4:Eu2+,Dy3+ is of special interest because of its high quantum efficiency,good stability and excellent persistent luminescence combined with an easy proces-sability.However the mechanism of afterglow phosphors is still unclear,even the effect of the reductive using on the producing process on the luminescence is not well studied.In this paper,compounds of SrAl2O4:Eu,Dy were prepared in air atmosphere by high temperature solid state reaction firstly,and then were treated in weak reductive atmosphere(95%N2+5%H2).Thirdly,in air atmosphere again,and finally,in weak reductive atmosphere(95%N2+5%H2).The effect of this process on the structure,luminescent properties,and themoluminescent spectra of the samples were studied by X-ray diffraction(XRD),fluorescent spectrophoto-meter and thermoluminescence dosimeter(TLD) respectively.The monoclinic structure remains the same irrespective of the process,and is in good agreement with that of the powder diffraction file(JCPDS) 34-0379(SrAl2O4).The reduction of Eu3+→Eu2+ was firstly observed in the aluminate phosphor of SrAl2O4:Eu,Dy synthesized in air condition and the reductive mechanism was also discussed in this paper.Eu3+ shows completely different luminescent properties with Eu2+ in SrAl2O4.Eu3+ has two narrow,intense spectra peaking at 592 nm and 612 nm,which resulted from the 5D0→7F1 transition and 5D0→7F4 transition respectively,implied that the Eu3+ may occupy two different lattice sites in the host crystal lattice;while Eu2+ has only one broad band spectra peaking at 513 nm,which resulted from the 4f65d→4f7 transition.The emission of Dy3+ was not found in all the four samples,indicated that the Dy3+ ions play a roll as trap centre in the phosphor,but not the luminescence centre.The concentration of Eu2+ in the samples treated in weak reductive atmosphere greatly increased whereas the concentration of Eu3+greatly decreased when compared to the samples treated in air atmosphere.The samples treated in weak reductive atmosphere have much higher thermoluminescent peak than that of the samples treated in air atmosphere.But all the samples,irrespective being treated in air atmosphere or reductive atmosphere,have the same trap depth(about 0.65 eV),which derived from Dy3+.All these phenomena indicated that,for the long after-glow phosphor material of SrAl2O4:Eu,Dy prepared in air atmosphere,the process of being treated in weak reductive atmosphere,air atmosphere and weak reductive atmosphere orderly,changes the valence of Eu ion and luminescence intensity,but doesn’t change the trap depth in the material.更多还原