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Optical Study of Vacuum-ultraviolet Fluoride Phosphors

真空紫外氟化物荧光粉的光学研究

基本信息

批准号：
15540322
负责人：
OHNO Nobuhito
金额：
$ 1.92万
依托单位：
Osaka Electro-Communication University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

The Xe dimer discharge fluorescent lamp is one of the leading candidates for alternative lighting devices to a conventional Hg discharge fluorescent lamp. In the Xe_2 discharge florescent lamps, phosphors are excited by vacuum ultraviolet (VUV) light peaking at 〜172nm. With the aim of developing practical Xe_2 discharge fluorescent lamps, new phosphors suitable for the conversion of VUV light into visible light have been extensively researched. In the Hg discharge fluorescent lamps, oxide phosphors have been employed so far. The oxide phosphors are unlikely to be suitable for the conversion of VUV light (〜172nm), because the VUV light is little absorbed by activators due to the absorption of oxide hosts. In contrast, most fluoride hosts are transparent down to 〜150nm, so that the VUV light directly excites activators in fluoride hosts. Metal ions with s^2 electronic configuration doped in insulating materials, called Tl^+-type ions, show several absorption bands originating from s^2→sp … More transitions. Since the s^2→sp transitions are dipole-allowed, the absorption is much stronger than that due to the f-f transitions. The strong absorption may give efficient conversion of the VUV light. However, electronic transitions in Tl^+-type ions doped in fluoride hosts have been less investigated so far.We have investigated luminescence and excitation spectra of Bi^<3+> ions doped in alkali yttrium fluorides (NaYF_4:Bi^<3+> and LiYF_4:Bi^<3+>), by mainly using synchrotron orbital radiation (UVSOR facility, Institute for Molecular Science, Okazaki, Japan). Bi^<3+> ions are trivalent Tl^+-type ions, so that can easily substitute for Y^<3+> ions. A broad and asymmetric luminescence band peaking at 〜430nm was observed in NaYF_4:Bi^<3+>, at room temperature. The radiative intra-ionic transition from a relaxed excited state (^3P_1) to a ground state (^1S_0) in Bi^<3+> ions is probably responsible for this luminescence band. In the excitation spectrum for the 430-nm luminescence, several excitation bands were observed below 300nm. These excitation bands originate likely from the transition from the ground state to some of the excited states given by the sp electronic configurations. The Tl^+-type ions doped in alkali halide crystals with NaCl-type structure show three characteristic absorption bands arising from the s^2→sp transitions, namely A, B and C bands. The A, B and C absorption bands are attributed to the transition to ^3P_1, ^3P_0, and ^1P_1 states, respectively. In Bi^<3+> ions doped in Cs_2NaYCl_6, The A and C bands have been observed at 〜320 and 220nm. In Bi^<3+> ions doped in fluorides hosts, the absorption bands would shift to the shorter wavelength side, as compared to those in chloride hosts. Less

汞二聚体放电荧光灯是替代传统汞放电荧光灯的照明设备的主要候选者之一。在Xe_2放电荧光灯中，荧光粉由峰值波长为172 nm的真空紫外光激发。为了研制实用的Xe_2放电荧光灯，人们对适用于真空紫外光到可见光转换的新型荧光粉进行了广泛的研究。在Hg放电荧光灯中，迄今为止已经使用氧化物磷光体。氧化物磷光体不太可能适用于VUV光（172 nm）的转换，因为VUV光由于氧化物基质的吸收而很少被活化剂吸收。相比之下，大多数氟化物基质在150 nm以下是透明的，因此VUV光直接激发氟化物基质中的活化剂。掺杂在绝缘材料中的具有s^2电子组态的金属离子，称为Tl^+型离子，显示出多个起源于s^2→sp的吸收带 ...更多信息过渡。由于s^2→sp跃迁是偶极允许的，所以吸收比f-f跃迁强得多。强吸收可以给出VUV光的有效转换。本论文主要利用同步轨道辐射（UVSOR装置，日本冈崎分子科学研究所）研究了Bi^<3+>离子在碱金属钇氟化物（NaYF_4：Bi^<3+>和LiYF_4：Bi^<3+>）中的发光和激发光谱。Bi^<3+>离子是三价的Tl^+型离子，因此可以很容易地取代Y^<3+>离子。室温下，在NaYF_4：Bi^<3+>中观察到一个宽的、不对称的发光带，峰位于λ 430 nm。Bi^<3+>离子从弛豫激发态（^3P_1）到基态（^1S_0）的离子内辐射跃迁可能是造成这一发光带的原因。在430 nm的激发光谱中，观察到几个低于300 nm的激发带。这些激发带起源于可能从基态的sp电子配置所给出的激发态的一些过渡。在NaCl型结构的碱金属卤化物晶体中，Tl^+型离子的s^2→sp跃迁产生了三个特征吸收带，即A、B和C带。A、B和C吸收带分别归因于到^3P_1、^3P_0和^1P_1态的跃迁。在Bi ~（3+）掺杂的Cs_2NaYCl_6中，在λ 320和220 nm处观察到A和C带。在氟化物基质中掺杂Bi^<3+>离子时，与氯化物基质中的吸收带相比，吸收带向短波长一侧移动。少