兰州大学机构库 >物理科学与技术学院
长余辉材料光谱调控和陷阱调节的研究
Alternative TitleTuning Spectral and Duration Properties of persistent luminescence phosphors
王振斌
Thesis Advisor张加驰
2017-05-25
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword长余辉 NaCa2GeO4F 热释光 缺陷
Abstract

1.通过传统的高温固相法我们成功的制备了性能优异的NaCa2GeO4F:Mn2+,Yb3+长余辉荧光粉,通过调控Mn2+发光中心的位置,长余辉的颜色能够实现从红色到黄绿色的调控,最大的移动范围达到50nm。有意义的是在紫外和人造日光源的激发下,长余辉荧光粉余辉时间分别达到20h和5 h。详细的研究了晶体结构、能带结构、荧光和磷光特性,通过一系列不同激发温度的热释实验,采用初升法分析陷阱特性,很好的解释了光谱移动和具有优异的余辉性能的原因。根据这个结果,我们制备的长余辉荧光粉NaCa2GeO4F:Mn2+,Yb3+能够作为一个优异的红色长余辉材料,并且有光存储应用前景。

2. 我们根据非等价取代诱导发光中心迁移的方法设计了一种高效的方法调节光谱和余辉性能,一系列的外加取代离子可以分为两类:RA (RA = Li+, Al3+, N3−, Ga3+, B3+) 和 RB (RB = Mg2+, F, Bi3+, Zn2+, Cd2+, Sc3+, Tm3+)。实验结果表明RA的非等价取代会引入带负电缺陷,并且稳定Mn2+发光中心在Na+/Ca2+格位发射红光。相比之下RB的非等价取代会引入带正电缺陷,诱导Mn2+发光中心从六配位的Na+/Ca2+ 格位迁移到四配位的Ge4+格位发射黄绿光。在掺杂过程中,共掺杂RA会使基质产生带正电的本征缺陷,将作为电子存储中心有利于余辉的产生,基于以上的结果,我们提出了一个可能的非等价取代诱导发光中心迁移机理,根据这个机理,可以实现光谱从568 ↔ 627 nm的双向调节,同时实现余辉时间从几分钟到6h的调节。

3.结合我们的实验数据和相关的参考文献,我们得到了Lu3Al2Ga3O12:Ln2+/Ln3+荧光粉的离子能级图。根据这个离子能级图,我们预测了在Lu3Al2Ga3O12:Ln2+/Ln3+ (Ln = La–Yb) 中外掺杂离子的余辉性能,在这个图中根据 Ln2+的4f能级位于带隙的位置可以评估Ln3+能否作为一个有效的外掺杂离子提高余辉,我们的实验结果证明了这个预测,最终证明Yb3+共掺杂在Lu3Al2Ga3O12:Tb3+荧光粉中能够作为一个有效的外掺杂离子提高余辉,系统的研究了外掺杂离子提高余辉的必要条件,对于余辉机理进行了详细的分析。

4.通过高温固相法合成了一种在Lu3Al5O12基质中掺杂Ce3+的黄绿色长余辉材料,Lu3Al5O12:Ce3+在380到480nm存在很强的吸收峰,在450nm的激发下,所有的样品发射波长为535nm的黄绿色光,余辉时间的最佳浓度时1.1%,在254 nm的激发下,样品Lu3Al5O12:1.1%Ce3+的余辉时间长达12h,为了进一步探究余辉机理,我们测试了热释光谱,研究发现,在掺Ce3+的样品中里面存在着2种缺陷,分析得出他们都属于本征缺陷。

Other Abstract

1.An excellent persistent luminescence (PersL) phosphor NaCa2GeO4F: Mn2+,Yb3+ has been synthesized by traditional solid-state reaction. By controlling the occupation sites of Mn2+ emitters, the PersL color of this phosphor can be optionally tuned in the red to green-yellow region, and the maximum spectral shift is more than 50 nm. Significantly, the red PersL can be measured for approximately 13 and 3 h (0.32 mcd/m2) and can be observed for more than 20 and 5 h with dark-adapted vision after exposure to ultraviolet irradiation and artificial sunlight, respectively. The crystal/electronic structure and photoluminescence/PersL properties of this phosphor have been investigated in detail. A series of the excitation temperaturedependent thermoluminescence experiments and the initial rising method have been conducted to study the trap properties of this phosphor. It reveals the reasons for the variation of PersL color, excellent red PersL, and degradation of green-yellow PersL. According to the results, the as-prepared NaCa2GeO4F:Mn2+,Yb3+ can be considered as an excellent red PersL phosphor, and it also has potential for application in optical storage.

2.We combine nonequivalent substitution and charge-induced emitter-migration approaches and design an efficient method to optionally tune the spectral and duration properties of NaCa2GeO4F:Mn2+ phosphor. A series of representative codopants have been investigated in detail and classified into two categories: RA (RA = Li+, Al3+, N3−, Ga3+, B3+) and RB (RB = Mg2+, F, Bi3+, Zn2+, Cd2+, Sc3+, Tm3+). Results reveal that the nonequivalent substitution of RA codopants would induce foreign negative defects and stabilize Mn2+ emitters at octahedral Na+/Ca2+ sites for red emission. In constrast, the RB codopants would generate foreign positive defects and make Mn2+ emitters migrate to tetrahedral Ge4+ sites for green-yellow emission. At the same time, the RA codopants are in favor of the generation of intrinsic positive traps with shallow trap depth and thus efficiently improve the duration properties of phosphors. On the basis of the experimental results, a possible nonequivalent substitution and charge-induced emitter-migration model has been proposed, and we can optionally tune the spectral (568 ↔ 627 nm) and the duration (minutes to more than 6 h) properties according to this model。

3.Spectroscopic data in our investigation, combined with those in references, are used to construct an energy diagram of the typical Lu3Al2Ga3O12:Ln2+/Ln3+ phosphors. Based on the diagram, the persistent luminescence properties of Lu3Al2Ga3O12: Ln2+/Ln3+ (Ln = La–Yb) phosphors are theoretically predicted. We have shown that the position of the 4f ground level of Ln2+ in the band gap can estimate the ability of Ln3+ codopants as foreign electron traps, and it is confirmed by our experimental results of the typical Lu3Al2Ga3O12:Tb3+,Ln3+ samples. Finally, the critical roles of the Yb3+ codopants as efficient foreign traps in the typical Lu3Al2Ga3O12:Tb3+ phosphor is revealed. The requirements for efficient foreign traps and the fundamental persistent luminescence mechanism of this phosphor are systematically summarized.

4.A green-yellow emitting PersL phosphor of Ce3+ doped Lu3Al5O12 was synthesized. Lu3Al5O12:Ce3+ showed an strong absorption band ranging from 380 to 480nm. Under 450nm excitation, all samples gave bright green-yellow emission peaked at 535nm. 1.1% concentration shown the optimal persistent luminescence behavior. Under sufficient 254 nm excitation, its afterglow can last for up to 12 hours. In order to further study, we use thermoluminescence to research trap information. There are 2 kinds of traps in Ce3+ codoped samples. They were due to intrinsic defects in this host.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/229022
Collection物理科学与技术学院
Recommended Citation
GB/T 7714
王振斌. 长余辉材料光谱调控和陷阱调节的研究[D]. 兰州. 兰州大学,2017.
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