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

我们一直在寻找对稀土离子(Gd^&lt；3+&gt；Gd^&lt；3+&gt；，Eu^&lt；3+&gt；和Pr^&lt；3+&gt；)表现出敏化效应的新型真空紫外线(VUV)激发材料，以实现白色荧光粉。在本研究中，我们研究了Sc(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))，其中主体对紫外光的吸收可能导致能量有效地转移到稀土离子(Gd^&lt；3+&Gt；，Tb^&lt；3+&Gt；，Eu^&lt；3+Gt；，和Pr^&lt；3+&gt；)。我们观察到了自陷态激子(STE)到Gd^&lt；3+&gt；，Tb^&lt；3+&gt；和Eu^&lt；3+&gt；离子的能量转移，并测定了它们的动力学。研究结果表明：(1)在紫外可见光区，硼酸锶(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))在紫外可见光区表现出宿主发射和这些h…的寿命已经确定了更多的最低排放量。宿主的发射被归因于由BO_3^&lt；3-&gt；或PO_4^&lt；3-&gt；基团的带隙激发或分子内跃迁引起的STE。Gd^&lt；3+&gt；，Tb^&lt；3+&gt；和Eu^&lt；3+&gt；的敏化作用已被证实，并测定了它们的动力学过程。(2)在真空紫外光激发下，未掺杂的LSB在315和366 nm处有本征宽的发射带。峰值位于315 nm的基质发射可以归属为STE的复合，这种复合可能与带隙激发或分子跃迁与BO_3^&lt；3-&gt；基团有关。在Gd^lt；3+和Tb^lt；3+&gt；掺杂样品(LSB：Gd和LSB：Tb)中，随着Gd^&lt；3+&gt；或Tb^&lt；3+&gt；或Tb^&lt；3+&gt；浓度的增加(5-50at.%)，基质发射减小，同时Gd^&lt；3+&gt；或Tb^&lt；3+&gt；的跃迁增加。这表明从宿主到Gd^&lt；3+&gt；离子的能量转移是有效的。此外，在Gd^&lt；3+或Tb^&lt；3+&gt；掺杂样品中，基质发射的衰减时间随着Gd^&lt；3+&gt；或Tb^&lt；3+&gt；浓度的增加而减小。这一发现为LSB：Gd和LSB：Tb中STE向Gd^lt；3+或Tb^lt；3+&gt；的能量转移提供了进一步的证据。通过时间分辨测量，确定了STE到Gd^&lt；3+&gt；和Tb^&lt；3+&gt；的能量转移速率。这些观测到的速率在估计的偶极-偶极能量转移速率的数量级内。测定了寄主排放的温度依赖性。结果表明，由于激子迁移率的原因，STE向Gd^&lt；3+&gt；和Tb^&lt；3+&gt；的能量转移是热激活的。(3)Gd^&lt；3+&gt；掺杂LSP和KSP中也观察到了真空紫外光激发下自陷态激子(STE)的能量转移。宿主到Gd^&lt；3+&Gt；的能量转移动力学。获得了基质发射(归属于STE)和激发光谱，以及157 nm激发的时间分辨发射。从时间分辨测量中，确定了主原子TO-Gd^&t；3+的能量转移率。根据估算的偶极-偶极能量转移速率与实验测量的发射强度随温度的变化关系，认为STE与LSb：Gd和LSb：Tb一样，发生了从STE到Gd^&lt；3+&Gt；的热激活能量转移过程。(4)在GdPO_4：Tb^&lt；3+&Gt；和Sr3Gd(PO_4)_3：Tb^&lt；3+&Gt；和Na_2GdF_2PO_4：Tb^&lt；3+&Gt；4f^8-4f^7-5d激发。当激发处于Tb^lt；3+>4f^75d态时，然后通过Tb^；lt；3+>3+>和/或Tb^；lt；3+>；3+^gt；>对Tb^^uv3+^gt；>对Tb^^V区域的主体晶格激发，激发能量直接转移到处于4f^75d态的Tb^⁷⁵3+^gt，或者首先转移到Tb^^G的^6G能级。在其4f^75d态，然后通过交叉弛豫能量传递来驰豫，就像在Tb^&lt；3+&gt；4f^7-5d态激发的那样。在Na2GdF2PO4：Eu3+&gt；中观察到Gd^&lt；3+&gt；到Eu^&lt；3+&gt；和Eu^&lt；3+&gt；的有效能量转移。较少

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