Dynamics of the host-sensitization by energy transfer from the self-trapped excitons and fabrication of novel white phosphors

自俘获激子能量转移的主体敏化动力学和新型白色荧光粉的制造

基本信息

批准号：
21360315
负责人：
KODAMA Nobuhiro
金额：
$ 8.82万
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：
2009
资助国家：
日本
起止时间：
2009 至 2011
项目状态：
已结题

项目摘要

We have been searching for new vacuum ultraviolet (VUV)-excited materials that exhibit a sensitization effect for rare-earth ions (Gd^<3+>, Tb^<3+>, Eu^<3+>, and Pr^<3+>) toward realizing white phosphors. In this study, we investigate scandium borate (LaSc_3(BO_3)_4 (LSB)) and phosphates (Li_3Sc_2 (PO_4)_3 (LSP), K_3Sc (PO_4)_2 (KSP), K_2CsSc(PO_4)_3 (KCSP)), and fluorozirconate (LaZr_2F_11 (LZF)), in which the absorption of VUV light by the host may lead to efficient energy transfer to rare-earth ions ( Gd^<3+>, Tb^<3+>, Eu^<3+> , and Pr^<3+> ). We observed energy transfer from the self-trapped exciton (STE) to Gd^<3+>, Tb^<3+>, and Eu^<3+> ions and we determined their dynamics. In this research the results obtained are as follows.(1) Scandium borate (LaSc_3(BO_3)_4(LSB)) and phosphates(Li_3Sc_2(PO_4)_3(LSP), K_3Sc(PO_4)_2(KSP), K_2CsSc(PO_4)_3 (KCSP)), and fuluorozirconate (LaZr_2F_11(LZF)) have been found to exhibit host emission in the UV-visible region and the lifetimes of these h … More ost emissions have been determined. The host emissions have been ascribed to STEs which are derived from band gap excitations or intramolecular transitions of the BO_3^<3-> or PO_4^<3-> group. Sensitizations of the Gd^<3+>, Tb^<3+>, and Eu^<3+> by energy transfer from the host excitations (STEs) have been demonstrated and their dynamics have been determined in these materials.(2) Under VUV-excitation, undoped LSB exhibits intrinsic broad emission bands at 315 and 366 nm. The host emission with a peak at 315 nm can be assigned to recombination of the STE that could be associated with band-gap excitations or molecular transitions with the BO_3^<3-> group. In Gd^<3+>-and Tb^<3+>-doped samples (LSB : Gd and LSB : Tb), host emission decreases with increasing Gd^<3+> or Tb^<3+> concentration (5-50 at.%) and this is accompanied by an increase in the transition of Gd^<3+> or Tb^<3+>. This suggests efficient energy transfer from the host to Gd^<3+> ions. In addition, in the Gd^<3+>-or Tb^<3+>-doped samples the decay time of the host emission decreases with increasing Gd^<3+> or Tb^<3+> concentration. This finding provides further evidence for energy transfer from the STE to Gd^<3+> or Tb^<3+> in LSB : Gd and LSB : Tb. From time-resolved measurements, the energy transfer rates from the STE to Gd^<3+> and Tb^<3+> were determined. These observed rates are within an order of magnitude of the estimated dipole-dipole energy transfer rates. The temperature dependences of the host emissions were determined. It was demonstrated that the energy transfers from STE to Gd^<3+> and Tb^<3+> are thermally activated probably due to exciton mobility.(3) Energy transfer from the self-trapped excitons (STE) upon VUV excitation was also observed in Gd^<3+>-doped LSP and KSP. The dynamics of the host-to-Gd^<3+> energy transfer. The host emission (ascribed to STE) and excitation spectra, as well as time-resolved emission excited at 157 nm were obtained. From time-resolved measurements, the energy transfer rate of the host.to-Gd^<3+> are determined. From a comparison of estimated dipole-dipole energy transfer rate with the experimentally measured temperature dependence of emission intensity, it was suggested that a thermally activated energy transfer process from the STE to Gd^<3+> occurs as with LSB : Gd and LSB : Tb.(4) Visible quantum cutting was observed in GdPO_4 : Tb^<3+> and Sr_3Gd(PO_4)_3 : Tb^<3+>, and Na_2GdF_2PO_4 : Tb^<3+> upon the host lattice and Tb^<3+> 4f^8-4f^7-5d excitations. Upon excitation at the Tb^<3+> 4f^75d state, then energy transfers via a cross relaxation process between a pair of Tb^<3+>.Tb^<3+> and/or Tb^<3+>.Gd^<3+> ; upon host lattice excitation in the VUV region, the excitation energy either directly transfers to a Tb^<3+> in its 4f^75d state or first transfer to the ^6G level of Gd^<3+> then to Tb^<3+> in its 4f^75d state, then relaxes via cross relaxation energy transfer as that excited at Tb^<3+> 4f^7-5d state. An efficient energy transfer from Gd^<3+> to Eu^<3+> and Eu^<3+> to Eu^<3+> was observed in Na_2GdF_2PO_4 : Eu_<3+>. Less

我们一直在寻找对稀土离子（Gd^<3+>、Tb^<3+>、Eu^<3+> 和 Pr^< 3+>）以实现白色荧光粉在这项研究中，我们研究了硼酸钪（LaSc_3(BO_3)_4 (LSB)）和磷酸盐（Li_3Sc_2）。 (PO_4)_3 (LSP)、K_3Sc (PO_4)_2 (KSP)、K_2CsSc(PO_4)_3 (KCSP)) 和氟锆酸盐 (LaZr_2F_11 (LZF))，其中主体对 VUV 光的吸收可能会导致高效能量转移至稀土离子（Gd^<3+>、Tb^<3+>、Eu^<3+>和 Pr^<3+> ）。我们观察到从自陷激子 (STE) 到 Gd^<3+>、Tb^<3+> 和 Eu^<3+> 离子的能量转移，并确定了它们的能量转移。本研究得到的结果如下：(1)硼酸钪(LaSc_3(BO_3)_4(LSB))和磷酸盐(Li_3Sc_2(PO_4)_3(LSP))， K_3Sc(PO_4)_2(KSP)、K_2CsSc(PO_4)_3 (KCSP)) 和氟锆酸盐 (LaZr_2F_11(LZF)) 已被发现在紫外-可见光区域表现出主体发射以及这些主体发射的寿命。已确定主体发射归因于源自带隙激发或分子内跃迁的STE。 BO_3^<3-> 或 PO_4^<3-> 基团通过宿主激发 (STE) 的能量转移对 Gd^<3+>、Tb^<3+> 和 Eu^<3+> 进行敏化。已经在这些材料中得到了证明，并且它们的动力学也已被确定。(2) 在 VUV 激发下，未掺杂的 LSB 在 315 和 366 nm 处表现出固有的宽发射带，主体发射峰为 300 nm。 315 nm 可以指定为 STE 的重组，该重组可能与带隙激发或 BO_3^<3-> 基团的 In Gd^<3+> 和 Tb^<3+> 掺杂样品的分子跃迁相关。（LSB：Gd 和 LSB：Tb），主体发射随着 Gd^<3+> 或 Tb^<3+> 浓度（5-50 at.%）的增加而减少，并且伴随着增加在 Gd^<3+> 或 Tb^<3+> 的转变中，这表明从主体到 Gd^<3+> 离子的有效能量转移。此外，在 Gd^<3+>-或 Tb^ 中。 <3+>掺杂样品的主体发射的衰减时间随着Gd^<3+>或Tb^<3+>浓度的增加而减少，这一发现为从STE到Gd^<3+>的能量转移提供了进一步的证据。或者LSB : Gd 和LSB : Tb 中的Tb ^ 3+ 从时间分辨测量，确定了从STE到Gd ^ 3+ 和Tb ^ 3+ 的能量转移速率。这些观察到的速率在范围内。确定了估计的偶极子-偶极子能量转移率的一个数量级。结果表明，从 STE 到 Gd^<3+> 和 Tb^<3+> 的能量转移是确定的。热激活可能是由于激子迁移率。(3)在Gd^3+掺杂的LSP和KSP中也观察到了VUV激发时自俘获激子(STE)的能量转移。主体到Gd的动力学。 ^ 3+ 能量转移。从时间分辨测量中获得了主体发射(归因于STE)和激发光谱以及在157nm处激发的时间分辨发射。通过比较估计的偶极子-偶极子能量转移率与实验测量的发射强度的温度依赖性，确定了来自STE的热激活能量转移过程。与LSB : Gd 和LSB : Tb 一样，发生到Gd^<3+> 的情况。 (4) 在GdPO_4 : Tb^<3+> 和LSB 中观察到可见量子切割。 Sr_3Gd(PO_4)_3 : Tb^<3+> 和 Na_2GdF_2PO_4 : Tb^<3+> 在主晶格和 Tb^<3+> 4f^8-4f^7-5d 激发下在 Tb^ 激发。 <3+> 4f^75d 状态，然后通过一对之间的交叉弛豫过程进行能量转移Tb^<3+>.Tb^<3+> 和/或 Tb^<3+>.Gd^<3+> ；在 VUV 区域中主晶格激发时，激发能量直接转移到 Tb^< 3+> 处于 4f^75d 状态，或者首先转移到 Gd^<3+> 的 ^6G 能级，然后转移到处于 4f^75d 状态的 Tb^<3+>，然后通过交叉松弛Tb^<3+> 4f^7-5d 态激发的弛豫能量转移从 Gd^<3+> 到 Eu^<3+> 和 Eu^<3+> 到 Eu^<3 的有效能量转移。 Na_2GdF_2PO_4:Eu_3+中观察到+>。