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

为了实现白色荧光体，我们一直在寻找对稀土离子（Gd^3+>、Tb^3 +>、Eu^3 +>和Pr^3+>）表现出敏化效果的新的真空紫外（VUV）激发材料。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）），其中基质对真空紫外光的吸收可以导致能量有效地转移到稀土离子（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，并确定了它们的动力学。在本研究中，所获得的结果如下。(1)硼酸钪（LaSc_3（BO_3）_4（LSB））、磷酸钪（Li_3Sc_2（PO_4）_3（LSP）、K_3Sc（PO_4）_2（KSP）、K_2CsSc（PO_4）_3（KCSP））和氟锆酸钪（LaZr_2F_11（LZF））在紫外-可见光范围内具有基质发光，它们的寿命分别为100 nm和200 nm，它们的发光强度分别为100 nm和200 nm。 关于我们 已经确定了ost排放量。基质发光被认为是BO_3 ~（2-）或PO_4 ~（2-）基团的带隙激发或分子内跃迁产生的STE<3-><3->。Gd^&lt;3+&gt;、Tb^&lt;3+&gt;和Eu^&lt;3+&gt;通过来自主体激发态（STE）的能量转移的敏化作用已经被证明，并且它们的动力学已经在这些材料中被确定。(2)在VUV激发下，未掺杂的LSB在315和366 nm处表现出本征宽发射带。在315 nm处有一个峰值的主体发射可以归因于STE的复合，这可能与BO_3 ~+基团的带隙激发或分子跃迁有关<3->。在Gd^&lt;3+&gt;和Tb^&lt;3+&gt;掺杂的样品（LSB：Gd和LSB：Tb）中，随着Gd^&lt;3+&gt;或Tb^&lt;3+&gt;浓度的增加（5-50 at.%），基质发射降低并且这伴随着Gd^&lt;3+&gt;或Tb^&lt;3+&gt;跃迁的增加。这表明从主体到Gd^&lt;3+&gt;离子的有效能量转移。此外，在Gd^&lt;3+&gt;或Tb^&lt;3+&gt;掺杂的样品中，基质发射的衰减时间随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中从STE到Gd^&lt;3+&gt;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，确定了从STE到Gd^&lt;3+&gt;和Tb^&lt;3+&gt;的能量转移速率。这些观察到的速率在估计的偶极-偶极能量转移速率的数量级内。确定了宿主发射的温度依赖性。结果表明，从STE到Gd^&lt;3+&gt;和Tb^&lt;3+&gt;的能量传递是热激活的，这可能是由于激子迁移率的缘故。(3)在Gd^3+掺杂的LSP和KSP中也观察到了真空紫外激发下自陷激子（STE）的能量转移。宿主-Gd^&lt;3+&gt;能量转移的动力学。获得了主体发射（归因于STE）和激发光谱，以及在157 nm处激发的时间分辨发射。从时间分辨的测量中，确定了基质到Gd ^&lt;3+&gt;的能量转移速率。通过比较估计的偶极-偶极能量转移速率与实验测量的发射强度的温度依赖性，我们认为从STE到Gd^&lt;3+&gt;的热激活能量转移过程与LSB：Gd和LSB：Tb一样。(4)在GdPO_4：Tb^&lt;3+&gt;、Sr_3Gd（PO_4）_3：Tb^&lt;3 +&gt;和Na_2GdF_2PO_4：Tb^&lt;3+&gt;中，观察到了在基质晶格和Tb^&lt;3+&gt; 4f^8-4f^7-5d激发下的可见量子剪裁。在Tb^&lt;3+&gt; 4f^75d态激发时，能量通过一对Tb^&lt;3+&gt;.Tb^&lt;3+&gt;和/或Tb^&lt;3+&gt;.Gd^&lt;3 +&gt;之间的交叉弛豫过程转移;在VUV区域中的主晶格激发时，激发能要么直接转移到Tb^&lt;3+&gt;的4f^75d态，要么先转移到Gd^&lt;3+&gt;的^6G能级，然后转移到Tb^&lt;3+&gt;的4f^75d态。7 - 5d态激发后，与Tb^&lt;3+&gt; 4f^7-5d态激发时一样，通过交叉弛豫能量转移弛豫。在Na_2GdF_2PO_4：Eu_（3+）中观察到Gd^&lt;3 +&gt;与Eu ^&lt;3+&gt;和Eu^&lt;3+&gt;与Eu^&lt;3 +&gt;的有效能量传递。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