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Development of VUV-excited phosphors based on correlation between quantum cutting and acceptor-site arrangement within coordination

基于量子切割和配位内受体位点排列之间的相关性开发真空紫外激发荧光粉

基本信息

批准号：
17360317
负责人：
KODAMA Nobuhiro
金额：
$ 10.3万
依托单位：
Akita University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

项目摘要

We study quantum cutting via downconversion for the couple of R_1^<3+>-R_2^<3+>, R_1^<3+>-R_2^<3+>-R_3^<3+> (R_1=Gd, R_2=Eu, Tb, R_3=Er), and R_2^<3+>-R_2^<3+> (R_2=Tb), and investigate the dynamics and mechanisms of the energy transfer of their systems. In this research the results obtained are as follows.(1) In CsGd_2F_7: Er^<3+>, Tb^<3+> and CsGd_<2-x>, Y_xF_7: Er^<3+>, Tb^<3+> (x=0.2-0.4) mixed phosphors, the quantum cutting effect takes place upon VUV excitation in the 4f_<10> 5d levels of Er^<3+>. The dependence of the cross-relaxation efficiency ηCR on the Er^<3+> and Tb^<3+> concentrations are examined. The cross-relaxation efficiency ηCR decreases for CsGd_2F_7: Er^<3+>, Tb^<3+> as Er^<3+> concentration increases. With increasing Tb^<3+> concentration, the cross-relaxation efficiency ηCR CsGd_2F_7: Er^<3+> Tb^<3+> passes through a maximum. The cross-relaxation efficiency ηCR for CsGd_<2-x> Y_xF_7: Er^<3+> (1at.%), Tb^<3+> (0.2at.%) mixed crystals decreases with increasing Y^<3 … More +> concentration. We have also investigated the dynamics of the quantum cutting in CsGd_2F_7: Er^<3+>, Tb^<3+> by means of measurements of time-resolved luminescence spectra. The experimentally observed decay curves are explained by the two energy-transfer processes. The present analysis provides more insight in the dynamics of down conversion processes in the quantum cutting model.(2) Visible quantum cutting upon VUV and short-UV excitations in the 4f^75d states of Tb^<3+> in CsGd_2F_7: Tb^3 and KGd_3F_10: Tb^<3+> CsGd_2F_7: Tb^<3+>, via downconversion mechanism has been observed. The dependence of the cross-relaxation efficiency ηCR on the Tb^<3+> concentrations is examined. The cross-relaxation efficiency ηCR for CsGd_2F_7: Tb^<3+> KGd_3F_10: Tb^<3+> and KGd_3F_10: Tb^<3+> fluorides increases with increasing Tb^<3+> concentration upon VUV and short-UV excitations at 172 nm and 212 nm. We have obtained a green-emitting quantum cutting phosphor CsGd_2F_7: Tb_<3+> for which the calculated ηCR achieves 0.53 and 0.64 for VUV excitations. The time-resolved emission spectra of Tb^<3+> in CsGd_2F_7: Tb^<3+> suggest the a two-step energy transfer process by cross relaxation and direct energy transfer from one Tb^<3+> to a neighbouring Tb^<3+> and/or a neighbouring Gd^<3+>, -downconversion mechanism as proposed in the quantum cutting model.(3) Visible quantum cutting through downconversion is observed for the Gd^<3+>-Eu^<3+> couple in KLiGdF_5: Eu^<3+> (KLGF: Eu^<3+>) In this Gd^<3+>-based fluoride, visible quantum cutting, occurs upon VUV excitation of Gd^<3+> at the 6G_J level via two-step energy transfer from Gd^<3+> to Eu^<3+> by cross-relaxation and sequential transfer of the remaining excitation energy. The dependence of the efficiency of cross-relaxation on the Eu^<3+> doping concentration is discussed in terms of the probability of energy transfer, and it is found that KLGF crystal doped with 2 at.% Eu^<3+> exhibits the maximum cross-relaxation efficiency of 0.4. Based on thr number of nearest neighbors around Gd^<3+> ions and the ^5D_0 emission intensity, energy transfer from excited Gd^<3+> ions appears to extend to the fourth-nearest Eu^<3+> neighbors in the quantum cutting process.(4)Ce^<3+> doped SrMgF_4 and BaMgF_4 crystals have the absorption and luminescence spectra in the VUV and UV ranges, respectively, so that wide pumping and tuning ranges are expended for laser operation. The persistent spectral hole burning (PSHB) in KLaF_4: Sm^<2+> has been observed at 12K. UV or visible excitation for Eu^<2+-> doped Ba_2SiO_4 and Ba_3SiO_5 crystals produces broadband luminescence in the green and yellow regions, respectively. The temperature dependence of the long-lasting phosphorescence suggest that electrons and holes produced by UV excitation move back to Eu^<2+> sites in the crystals through hopping and tunneling, and recombine radiatively at Eu^<2+>. Less

我们研究了R_1^<3+>-R_2^<3 +>、R_1^<3+>-R_2 ^<3+>-R_3^<3+>（R_1=Gd，R_2=Eu，Tb，R_3=Er）和R_2^<3+>-R_2 ^<3 +>（R_2=Tb）对的下转换量子剪裁，探讨了它们的能量传递动力学和机制。在本研究中，所获得的结果如下。(1)在CsGd_2F_7：Er^<3+>、Tb^<3+>和CsGd_<2-x>，Y_xF_7：Er^<3+>、Tb^<3+>（x=0.2-0.4）混合荧光粉中，在真空紫外激发下，<10>Er^<3+>的4f_ 5d能级发生量子切割效应。研究了交叉弛豫效率ηCR与Er^<3+>和Tb^<3+>浓度的关系。CsGd_2F_7：Er^<3+>，Tb^<3 +>的交叉弛豫效率ηCR随Er^<3+>浓度的增加而减小。随着Tb^<3+>浓度的增加，交叉弛豫效率ηCR CsGd_2F_7：Er^<3+> Tb^<3+>经历一个极大值。计算了CsGd_<2-x>Y_xF_7：Er^<3+>（1at.%）的交叉弛豫效率ηCR，Tb^<3+>（0.2at.%）随着Y^<3，混晶减少 ...更多信息 +>浓度。我们还通过时间分辨荧光光谱的测量研究了CsGd_2F_7：Er^<3+>，Tb^<3+>的量子剪裁动力学。实验观察到的衰减曲线解释的两个能量转移过程。目前的分析提供了更多的洞察力在量子切割模型中的下转换过程的动力学。(2)在CsGd_2F_7：Tb^<3+>和KGd_3F_10：Tb^<3 +> CsGd_2F_7：Tb^<3+>中，观察到了Tb^<3+> 4f^75d激发态通过下转换机制的可见光量子剪裁。研究了交叉弛豫效率ηCR与Tb^<3+>浓度的关系。在172 nm和212 nm的真空紫外和短紫外激发下，CsGd_2F_7：Tb ^<3 +>、KGd_3F_10：Tb ^<3+>和KGd_3F_10：Tb^<3 +>氟化物的交叉弛豫效率ηCR随Tb^<3+>浓度的增加而增加。我们得到了一种绿色荧光粉CsGd_2F_7：Tb_（3+），在真空紫外激发下，计算的ηCR分别达到0.53和0.64。在CsGd_2F_7：Tb^<3 +>中Tb^<3 +>的时间分辨发射光谱表明，在量子切割模型中，Tb^<3+>与相邻Tb^<3+>和/或相邻Gd^<3+>之间存在交叉弛豫和直接能量转移两步能量转移过程。(3)在KLiGdF_5：Eu^<3 +>中观察到了Gd^<3+>-Eu^<3 +>对的可见光量子下转换切割（KLGF：Eu^<3+>）在该Gd^<3+>基氟化物中，可见量子切割，当Gd^<3+>在6G_J能级上被真空紫外激发时，通过两步能量转移从Gd^<3+>到Eu^<3+>，剩余激发能的弛豫和顺序转移。从能量转移几率的角度讨论了交叉弛豫效率与Eu^<3+>掺杂浓度的关系，发现掺杂浓度为2at.% Eu^（3+）表现出最大的交叉弛豫效率为0.4。根据Gd^<3+>离子的近邻数和^5D_0发射强度，在量子切割过程中，Gd^<3+>离子的能量转移似乎扩展到了Eu^<3 +>离子的第四近邻。(4)Ce SrMgF_4和BaMgF_4晶体的吸收光谱和发光光谱分别在真空紫外和紫外波段，从而扩大了激光器的泵浦和调谐范围。在KLaF_4：Sm^<2+>中观察到了12 K下的持续光谱烧孔现象。Eu^（2+）掺杂的Ba_2SiO_4和Ba_3SiO_5晶体在紫外或可见光激发下分别在绿色和黄色区产生宽带发光。长余辉发光的温度依赖性表明，紫外光激发产生的电子和空穴通过跳跃和隧穿回到晶体中的Eu^2+位置，并在Eu^2+处辐射复合。少