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

我们研究了通过下转换对 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)，并研究其动力学和机制本研究得到如下结果：(1)CsGd_2F_7中：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，VUV激发时在4f_<10> 5d能级产生量子切割效应研究了交叉弛豫效率 ηCR 对 Er^<3+> 和 Tb^<3+> 浓度的依赖性 CsGd_2F_7: Er^<3 的交叉弛豫效率 ηCR 降低。 +>、Tb^<3+> 随着 Er^<3+> 浓度的增加而增加，交叉弛豫效率 ηCR 随 Tb^<3+> 浓度的增加而增加。 CsGd_2F_7: Er^<3+> Tb^<3+> 通过最大值 CsGd_<2-x> Y_xF_7: Er^<3+> (1at.%), Tb^<3 +> (0.2at.%) 混合晶体随着 Y^<3 … More +> 浓度的增加而减少。我们还研究了量子切割的动力学。 CsGd_2F_7: Er^<3+>, Tb^<3+> 通过时间分辨发光光谱的测量实验观察到的衰减曲线通过两个能量转移过程进行了解释。本分析提供了对动力学的更多见解。 (2) Tb^<3+> 4f^75d态下VUV和短UV激发下的可见量子切割CsGd_2F_7: Tb^3 和 KGd_3F_10: Tb^<3+> CsGd_2F_7: Tb^<3+>，通过下转换机制观察了交叉弛豫效率 ηCR 对 Tb^<3+> 浓度的依赖性。 CsGd_2F_7 的交叉弛豫效率 ηCR: Tb^<3+> KGd_3F_10: Tb^<3+> 和 KGd_3F_10: Tb^<3+> 氟化物在 172 nm 和 212 nm 的 VUV 和短紫外激发下随着 Tb^<3+> 浓度的增加而增加。切割荧光粉CsGd_2F_7：Tb_<3+>，计算出的ηCR达到0.53， CsGd_2F_7 中 Tb^<3+> 的时间分辨发射光谱为 0.64：Tb^<3+> 表明通过交叉弛豫和来自 Tb^<3+ 的直接能量转移的两步能量转移过程。 > 到相邻的 Tb^<3+> 和/或相邻的 Gd^<3+>，量子切割模型中提出的下转换机制。 (3) 可见光量子切割通过下转换观察到 KLiGdF_5 中的 Gd^<3+>-Eu^<3+> 对：Eu^<3+> (KLGF: Eu^<3+>) 在这种基于 Gd^<3+> 的氟化物中，可见光量子切割，发生在 6G_J 能级的 Gd^<3+> 的 VUV 激发下，通过从 Gd^<3+> 到 Eu^<3+> 的两步能量转移：从能量转移的概率角度讨论了交叉弛豫效率对Eu^<3+>掺杂浓度的依赖性，发现KLGF晶体掺杂。具有 2 at.% Eu^<3+> 的最大交叉弛豫效率为 0.4。基于 Gd^<3+> 离子周围最近邻的数量和 ^5D_0 发射强度、能量转移。在量子切割过程中，激发的Gd^<3+>离子似乎延伸到第四最近的Eu^<3+>邻居。(4)Ce^<3+>掺杂的SrMgF_4和BaMgF_4晶体具有吸收光谱和发光光谱分别在 VUV 和 UV 范围内，从而扩展了 KLaF_4 中的持久光谱烧孔 (PSHB) 的宽泵浦和调谐范围：在12K紫外或可见光激发下观察到Eu^<2+->掺杂的Ba_2SiO_4和Ba_3SiO_5晶体分别在绿色和黄色区域产生宽带发光。表明紫外激发产生的电子和空穴通过跳跃和隧道效应移回晶体中的Eu^2+位点，并在小于Eu^<2+>。