Optical energy storage-type tunable long-lasting phosphorescence of low valent rare-earth ions using crystal-field distributions

利用晶体场分布的低价稀土离子光储能型可调谐长余辉磷光

• 批准号: 12650665
• 负责人: KODAMA Nobuhiro
• 金额: $ 2.24万
• 依托单位: Akita University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650665/
• 关键词: Spectrocopy; Ciystal field; Phosphorescence; Single crystal; Crystal growth; Structure analysis; 希土類イオン

Low valent rare-earth ions(Eu^<2+>,Ce^<3+>,Sm^<2+>) in crystals with crystal-field distributions are expected to produce long-lasting phosphorescence in visible region and to show novel optical phenomena. We have prepared new melilite-type aluminosilactes with disordered stuructures, Ba silicates, and fluondes with superstructures. We have examined the optical properties, the local structures, and the mechanism of long-lasting phosphorescence and photoreaction produced by the incoherent UV light or near IR femtosecond laser excitaion. The results of this study are summarized as follows.1. UVexcitation for new Eu^<2+>-doped melilite Me_2A_3O_7(Me=Ca,Sr,Y,Gd;B=Al,Si) produces long-lasting phpsphorescence from Eu<2+> ions in the blue and bitter orange regions. The temperature dependence is derived from decay rates including both radiative and non-radiative processes. We proposed the following model of the phosphorescence of Eu^<2+> in the melilite crystals.(1) Pairs of electrons and holes … More are produced at Eu^<2+> ions by the UV excitation, move to stable trapped centers.(2) The electrons or holes again back to Eu^<2+> through thermal hopping ana tunneling, and recombine radiatively.2. Long-lasting phosphorescence in the blue and bitter orange regions has been observed for newly discoverd Eu^<2+>-doped Ba-silicates(Ba_2SiO_4, BaSi_2O_5,Ba_3SiO_5). The decay is due to the recombination of the electron-hole pairs through tunneling.3. Trivalent Eu^<3+> -doped Ca_2Al_2SiO_7 melilite single crystals were grown. Infrared femto-second laser-induced bright and long-lasting phosphorescence in the red region was observed. This is first obsevation of long-lasting phosphorescence of trivalent Eu^<3+> in the red region by the infrared laser excitation.4. UV excitation of Ce^<3+>-doped melilite crystals Ca_2Al_2SiO_7 and CaYAl_3O_7 produces long-lasting phosphorescence besides intrinsic Ce^<3+> luminescence. The phosphorescence is explained by a model of the recombination of distant paires of trapped electrons and holes. The self -trapped holes, Al^<4+>, produced by the UV excitation move back to Ce^<3+> sites throug tunneling and thermal hopping, and the trapped holes of Ce^<4+> recombine radiatively the trapped electrons in the form of F^+ centers through tunnling. It is strongly related to hopping between the adiacent self-trapped staes of holes speparated by a barrier with the activetion energy.5. New phosphors, Ce^<3+> -and Sm^<3+>Sm^<2+>-doped BaMgF_4 and Ce^<3+>-doped CaNaYF6 were grown. Ce^<3+>-doped BaMgF_4 crystal exmoits a commensurate supser siruciurre. After the irradiation by the femtosecond laser, a part of Sm^<3+> in BaMgF_4 was converted to Sm^<2+>. The BaMgF_4:Sm^<3+>/Sm^<2+> crystal nas a potential for applications in opucai siorage. the effects of disorder in the CaNaF_6 crystal on the inhomogeneous brodening of the Ce^<3+> luminescence was analyzed. The Ce^<3+>-doped CaNaYF_6 crystal has a potential as a new material capable of lasing with wider tunability from the near UV to green regions. Less

具有晶体场分布的晶体中的低价稀土离子(Eu^<2+>、Ce^<3+>、Sm^<2+>)有望在可见光区域产生持久的磷光并表现出新颖的光学现象。我们制备了具有无序结构的新型黄长石型铝硅酸盐、硅酸钡和具有超结构的氟化物。我们研究了非相干紫外光或近红外飞秒激光激发产生的光学性质、局部结构以及持久磷光和光反应的机制。本研究的结果如下： 1．新的Eu^<2+>掺杂黄长石Me_2A_3O_7(Me=Ca,Sr,Y,Gd;B=Al,Si)的UV激发在蓝色和苦橙色区域由Eu<2+>离子产生持久的磷光。温度依赖性源自衰变率，包括辐射和非辐射过程。我们提出了黄长石晶体中Eu^<2+>的磷光模型。(1)Eu^<2+>离子在紫外激发下产生电子和空穴对，移动到稳定的俘获中心。(2)电子或空穴通过热跳跃和隧道效应再次回到Eu^<2+>，并辐射复合。2．新发现的Eu^2+掺杂Ba硅酸盐(Ba_2SiO_4、BaSi_2O_5、Ba_3SiO_5)在蓝色和苦橙色区域观察到长效磷光。衰变是由于电子-空穴对通过隧道效应的复合所致。3．生长了三价Eu 3+ 掺杂的Ca_2Al_2SiO_7黄长石单晶。在红色区域观察到红外飞秒激光诱导的明亮且持久的磷光。这是首次在红外激光激发下观察到三价Eu^3+在红光区长余辉磷光。4． Ce^<3+>掺杂的黄长石晶体Ca_2Al_2SiO_7和CaYAl_3O_7的紫外激发除本征Ce^<3+>发光外还产生持久的磷光。磷光可以通过远距离捕获的电子和空穴对的复合模型来解释。紫外激发产生的自陷空穴 Al^<4+> 通过隧道效应和热跳跃移回 Ce^<3+> 位点，Ce^<4+> 的陷空穴通过隧道效应以 F^+ 中心的形式与捕获的电子进行辐射复合。它与由具有活化能的势垒隔开的相邻自陷空穴之间的跳跃密切相关。 5．生长了新的磷光体，Ce ^ 3+ -和Sm ^ 3+ -Sm ^ 2+ -掺杂的BaMgF_4和Ce ^ 3+ -掺杂的CaNaYF 6 。 Ce 3+ 掺杂的BaMgF_4晶体表现出相当的超级晶体。经过飞秒激光照射后，BaMgF_4中的部分Sm^3+转化为Sm^2+。 BaMgF_4:Sm^<3+>/Sm^<2+>晶体具有在opucai贮藏中应用的潜力。分析了CaNaF_6晶体的无序性对Ce^3+发光不均匀溴化的影响。 Ce^3+掺杂的CaNaYF_6晶体具有作为新材料的潜力，能够以更宽的可调性从近紫外到绿光区域发射激光。较少的

项目成果

Mitsuo Yamaga: "Mechanism of Long-Lasting Phosphorescence process of Ce^<3+> -doped Ca_2Al_2SiO_7 Crystals"Journal of physics : Condensed Matter. (in press). (2002)

Mitsuo Yamaga：“Ce^3>掺杂Ca_2Al_2SiO_7晶体的长持续磷光过程的机制”物理学杂志：凝聚态物质。

Nobuhiro Kodama: "Optical and structural studies on BaMgF_4:Ce^<3+>"J. Crystal Growth. 229. 492-496 (2001)

Nobuhiro Kodama：“BaMgF_4:Ce^<3>的光学和结构研究”J。

Nobuhiro Kodama: "Optical and Structural studies on BaMgF4 : Ce^<3+> crystals"Journal of Crystal Growth. (in press). (2001)

Nobuhiro Kodama：“BaMgF4 : Ce^<3> 晶体的光学和结构研究”晶体生长杂志。

Mitsuo Yamaga: "Super structure of Ce^<3+>-doped BaMgF4 fluoride crystals-x-ray diffraction, ESR, and optical investigations"Journal of physics : Condensed Matter. 13. 10811-10824 (2001)

Mitsuo Yamaga：“Ce^3>掺杂的BaMgF4氟化物晶体的超结构-X射线衍射、ESR和光学研究”物理学杂志：凝聚态物质。

Nobuhiro Kodama: "Monoclinic Superstructure of SrMgF4 with Perovskite-type Slabs"Acta Crystallographica C. 57. 784-786 (2001)

Nobuhiro Kodama：“具有钙钛矿型板的 SrMgF4 的单斜超结构”Acta Crystallologica C. 57. 784-786 (2001)