YAlO3晶体中pr3+的4f2能级

YAlO3∶pr3+是一种受到广泛关注的发光体系,本文根据文献中给出的YAlO3∶pr3+晶体中Pr3+的晶体场能级,从Nd3+离子的晶体场参数和Pr3+的准自由离子参数出发,采用f-shell计算软件包对pr3+的能级参数进行了研究,并对获得的参数进行了讨论.用拟合获得的参数计算了pr3+的4f2电子构型的所有能级.     

不同壳层厚度的LaF3：Eu3+/LaF3核壳结构纳米颗粒制备及发光性质

表面缺陷会使纳米材料的发光中心产生严重的猝灭，而适当厚度的同质包覆层会减少其猝灭。本文利用共沉淀法合成了LaF₃：Eu³⁺纳米颗粒和LaF₃：Eu³⁺/LaF₃核壳结构纳米颗粒，研究了颗粒的晶体结构、形貌以及不同壳层厚度对发光性能的影响。研究发现：LaF₃：Eu³⁺核心和LaF₃：Eu³⁺/LaF₃核壳结构均为六方结构。包覆同质壳层可以提高稀土离子的发光性能，包覆厚度的不同导致LaF₃：Eu³⁺/LaF₃核壳结构的荧光强度与衰减时间均发生改变。其原因是未掺杂的LaF₃壳层可以将发光中心Eu³⁺离子与LaF₃：Eu³⁺核心的表面隔离，进而减少表面对发光中心的猝灭，提高材料的发光性能。这种修饰作用与壳层厚度相关。     

用于液体激光介质的Nd~(3+)离子掺杂氟化镧纳米颗粒的制备与性能表征

设计并合成了掺杂不同Nd3+离子浓度的氟化镧纳米颗粒,并用油酸进行了表面修饰,使得这类纳米颗粒可分散于常见的有机溶剂中形成透明、均一、稳定的溶液。对纳米颗粒的结构、晶相以及发光性能进行了表征。固体和溶液材料在1 060 nm都有强的发射峰,说明纳米晶格可有效地保护Nd3+离子免受外界环境对发光的猝灭影响。纳米颗粒有机溶液的吸收损耗和散射损耗测试结果表明,其总损耗系数能够满足激光介质材料的损耗要求,为该材料的实用化打下了基础。     

Zn,Cd对CaTiO3：Pr3+的发光性质的影响

采用高温固相反应合成CaTiO₃:Pr³⁺、Zn₂TiO₄、Ca_0.7Zn_0.3-xCd_xTiO₃:Pr³⁺(x=0.01,0.03,0.05,0.07,0.09,0.1)红色系列粉末状发光材料。经X射线衍射检测其结构,CaTiO₃结构为正交晶系,其结果与JCPDS标准卡(42-423)相符。Zn₂TiO₄结构属立方晶系,结果与JCPDS标准卡(25-1164)一致。Ca_0.7Zn_0.3-xCd_xTiO₃:Pr³⁺(x=0.01,0.03,0.05,0.07,0.09,0.1)由两种物相组成,一种为CaTiO₃,另一种为Zn₂TiO₄。检测了材料的激发光谱和发射光谱。发现,在CaTiO₃:Pr³⁺中加入适量Zn可形成Zn₂TiO₄相,使材料的激发光谱在324nm附近的吸收增强。少量Cd可进入Zn₂TiO₄晶格,增强激发光谱在324nm附近的吸收,同时提高发射光谱的强度;但过量的Cd的加入会导致发射光谱强度下降。     

SrB4O7：Pr3+,Mn2+中的Pr→Mn能量传递

从能量传递的角度出发,利用同步辐射光源(德国HASYLAB实验室的SUPERLUMI实验站)对Pr³⁺和Mn²⁺掺杂的SrB₄O₇粉末样品进行了光谱研究.206nm激发下,在SrB₄O₇:Pr³⁺(0.1%,摩尔分数)样品中观察到了来自Pr³⁺离子1S0能级的光子级联发射.SrB₄O₇:Pr³⁺样品的发射谱与SrB₄O₇:Mn²⁺样品监测Mn²⁺离子640nm发射的激发谱在330~430nm的波长范围里存在显著的光谱重叠.这个光谱重叠有利于Pr³⁺→Mn²⁺的能量传递发生,从而将Pr³⁺离子级联发射中第一步不实用的紫外或近紫外光子转换为Mn²⁺的红光发射.双掺杂样品SrB₄O₇:Pr³⁺,Mn²⁺与单掺杂样品SrB₄O₇:Pr³⁺的发射谱比较揭示出Pr³⁺→Mn²⁺的能量传递的确存在,并且提供了一种传递效率的估算方法,表明通过“Pr³⁺-Mn²⁺”组合有可能获得量子效率大于1的高效真空紫外激发发光材料.     

ZBLAN玻璃中Pr3+掺杂离子3P0和1D2能级的发光特性和寿命

对ZBLAN氟锆酸盐玻璃中Pr³⁺掺杂离子³P₀和¹D₂能级的寿命和发光特性进行了较详细的光谱学研究。首先测量了两种掺杂浓度(质量分数分别为1×10^-3,5×10^-3)的Pr³⁺:ZBLAN玻璃的吸收光谱,然后运用时间分辨激光光谱技术测量了³P₀和¹D₂能级在激光单光子共振激发下的荧光发射谱和能级寿命。将不同荧光发射谱带的强度和文献报道的Judd Ofelt理论计算辐射跃迁几率数值做了比较分析,证明了文献中理论计算结果的可靠性。由于浓度猝灭效应,在相同的激发条件下,掺杂浓度为1×10^-3样品的荧光发射强度明显大于5×10^-3样品的荧光发射强度。但是从我们的测量结果看,掺杂浓度对³P₀和¹D₂ 的能级寿命值无显著影响。掺杂浓度为1×10^-3时,Pr³⁺离子³P₀和¹D₂能级的寿命值分别为46,322μ_s。     

Yb3+：Pr3+：ZBLAN光纤中4f5d上转换激发的理论研究

利用粒子数速率方程和相关的辐射跃迁理论,计算了Yb³⁺:Pr³⁺:ZBLAN光纤中Pr³⁺离子4f5d能级两步上转换激发的动力学过程.得到不同Pr³⁺掺杂浓度下,激发光的光谱强度和粒子数密度的纵向分布和有效光纤长度随激发光的光谱强度的变化关系.另外,还得到了4f5d荧光强度与入射光强、光纤长度和Pr³⁺掺杂浓度的关系,给出了激发效率与激发光的光谱强度和Pr³⁺掺杂浓度的关系.     

Vacuum ultraviolet spectroscopy of Pr in CaAl4O7, LaMgAl11O19 and SrLaAlO4

The vacuum ultraviolet spectroscopy of Pr³⁺ doped CaAl₄O₇, LaMgAl₁₁O₁₉ and SrLaAlO₄ is reported. It appears that whenever the aluminate host lattice is excited directly, mainly exciton and 4f²–4f² [³P₀] Pr³⁺ emission are observed. When the excitation energy is lower, Pr³⁺ ions are excited selectively and 4f5d–4f² emission dominates. These observations can be explained by assuming that energy transfer from the host lattice to the Pr³⁺ ion takes place preferentially via an intermediate exciton state with an energy too low to reach the energetic Pr³⁺ 4f5d excited states.     

Si,Lu掺杂Ca0.8Zn0.2TiO3:Pr3+荧光粉的光学性能改善

采用高温固相法合成Ca_0.8Zn_0.2TiO₃：0.2% Pr³⁺,Si⁴⁺和Ca_0.8Zn_0.2TiO₃：0.2% Pr³⁺,Si⁴⁺,Lu³⁺荧光粉。通过X射线衍射仪、电子顺磁共振光谱仪、显微拉曼光谱仪和荧光光谱仪等表征了该系列荧光粉的物相组成、微观结构和发光性质。结果表明,以β-Si₃N₄为硅源制备的荧光粉具有最佳的光学性能。加入ZnO后,荧光粉由CaTiO₃、Zn₂TiO₄和Ca₂Zn₄Ti₁₆O₃₈三相组成,其中CaTiO₃为主相。电子顺磁共振谱证实了Pr⁴⁺存在,Lu³⁺的添加使[Pr⁴⁺Ti³⁺O₃]⁺簇显著增加,电子顺磁共振谱和拉曼光谱均证实Si⁴⁺、Lu³⁺的掺杂使局部TiO₆簇对称性提高,有利于Pr³⁺发光中心的能量传递。在336 nm激发下,荧光粉展示了很强的位于612 nm的红光发射（归属于Pr³⁺的¹D₂→³H₄跃迁）及理想的红光色坐标（x=0.670,y=0.330）。Si⁴⁺和Lu³⁺的添加显著增强了370 nm激发下红光发射,Ca_0.8Zn_0.2TiO₃：0.2% Pr³⁺,3.2% Si⁴⁺荧光粉的余辉寿命最长。     

高量子效率的近红外量子裁剪材料LaF3:Ho3+,Yb3+的合成及其发光性能

采用共沉淀法合成了LaF₃∶Ho³⁺,Yb³⁺ 红外下转换材料,研究了室温下该材料的激发光谱、发射光谱特性和发光的时间衰减曲线。在LaF₃∶Ho³⁺,Yb³⁺ 粉末中,观察到了Ho³⁺ 到Yb³⁺ 的能量传递,并通过分析确认了其为共振能量传递。通过Ho³⁺ 到Yb³⁺ 的共振能量传递过程,可以将材料吸收一个300~360 nm波段的紫外光子转化为两个波长在1 μm附近的红外光子。Yb³⁺ 的发射正好与硅太阳能电池的吸收匹配,材料中的这一红外下转换现象对于提高硅太阳能电池的效率具有积极意义。     

Luminescence of rare-earth ions in perovskite-type oxides: from basic research to applications

Luminescence of a rare-earth ion in SrTiO₃ or other perovskite-type oxides was used as a probe of physical properties of a host crystal, but not as a phosphor because observed luminescence efficiency was low. Recent investigations have shown that the luminescence efficiency of SrTiO₃:Pr³⁺ is intensified up to 200 times by addition of Al ions. This paper reviews experimental results on this phenomenon and discusses mechanism of the Al-addition effect. A survey was made to find other materials, the efficiency of which can be improved by the impurity addition. Host-to-activator energy transfer by a coupling of the band-edge recombination energy and an allowed transition of a rare-earth ion is essential to provide a high efficiency. A red phosphor, Al-added SrTiO₃:Pr³⁺, is promising for display applications.     

PrNi$lt;sub$gt;2$lt;/sub$gt;的磁和磁热性能研究

在一些磁性材料内, 磁性离子间交换作用和磁性离子的自旋涨落对材料磁性有影响. 本文根据磁比热实验值确定了晶场参数后, 利用包含自旋涨落的交换作用有效场H_m= n₀ (1 + γ T + β e^{ω T})M, 计算了PrNi₂晶体晶场能级的Zeeman劈裂. 在温度为3.8 K ≤T≤ 30 K范围内, 计算了该晶体多晶磁矩随外磁场的变化, 以及外磁场H=5000 Oe时磁化率倒数随温度的变化, 计算结果和实验值符合较好. 当外磁场在0–50000 Oe时, 计算的该晶体的磁熵变与已有文献的理论结果相似. 计算结果说明, 提出的包含自旋涨落的交换作用有效场不仅适合亚铁磁性晶体, 而且也适合顺磁性晶体. 关键词： 2')" href="#">PrNi₂ 磁比热 交换作用有效场 磁矩 磁熵变     

2018年7期 电子期刊

采用自蔓延燃烧法制备了不同镨掺杂浓度的12CaO·7Al₂O₃：Pr³⁺（C12A7：Pr³⁺） X射线影像存储荧光粉。在232 nm激发下,发现Pr³⁺掺杂摩尔分数为0.3%的荧光粉位于486 nm的蓝光发射峰呈现最大的发光强度。对C12A7：0.3% Pr³⁺样品进行真空热处理后,C12A7笼中的O^2-基团数量减少,同时类F⁺色心的空笼子的数量增多,导致陷阱数目增加和光激励发光强度增大。热释发光实验表明：C12A7：0.3% Pr³⁺样品中存在两个深陷阱,陷阱深度分别约为0.69 eV和0.80 eV;经过真空热处理后的C12A7：0.3% Pr³⁺荧光粉,陷阱深度变深,陷阱数目增多,光存储性能变好。当吸收的X射线剂量为5.2 Gy时,可以实现分辨率较高的X射线成像。实验结果表明,镨掺杂C12A7荧光粉在计算机X射线摄影领域有潜在的应用前景。     

Optical and dosimetric properties of variously doped SrF2 crystals

Optical properties and irradiation effects of Nd³⁺-, Pr³⁺-, Tb³⁺- and Tm³⁺-doped SrF₂ crystals and their possible application to solid-state dosimetry were studied and compared to those induced in pure SrF₂ crystals. Optical absorption, thermoluminescence (TL), X- and light-induced luminescence (XL and PL) as well as optically stimulated luminescence and phototransferred TL (OSL and PTTL) were measured in the various samples. Special attention was given to effects of monochromatic vacuum ultraviolet (VUV) radiation. TL was excited in the pure and doped samples by X and β rays as well as by VUV radiation. TL peaks appeared after VUV irradiation at the same temperatures and with the same thermal activation energies as after X or β irradiation, indicating that they are due to the same processes. The VUV excitation spectra showed two maxima at about 145 and 130 nm. Comparison of the TL sensitivities of the various TL materials, showed that the sensitivity of SrF₂:Pr³⁺ was by more than an order of magnitude higher than that of the known LiF:Mg,Ti (TLD-100) phosphor. The sensitivity of pure and of the Nd, and Tb-doped SrF₂ were by a factor of 2–4 higher than that of the TLD-100 and that of SrF₂:Tm was slightly lower. The main emission bands of SrF₂:Pr³⁺ are located in a convenient spectral region between 460 and 640 nm, where most of the standard photomultipliers are sensitive. The dose dependence of the 460 K TL peak in SrF₂:Pr³⁺ is nearly linear in a wide range up to above 27 000 Gy.     

双波长Pr3+掺杂12CaO·7Al2O3的光存储特性

采用化学共沉淀法制备了Pr3+掺杂的12CaO·7Al2O3(C12A7:Pr3+)材料.通过X射线衍射(XRD)、发射光谱、激发光谱、余辉衰减曲线、热释发光及光激励发光等测试手段系统研究了C12A7:Pr3+材料的微观结构和光学性质.结果表明,C12A7是一种理想的适合Pr3+掺杂的基质材料,C12A7:Pr3+具有...     

Conversion of VUV to UV and visible in K5Li2LnF10 containing rare-earth from cerium group (Ln=La, Ce, Pr, Nd)

The potential of single crystals K₅Li₂LnF₁₀, for applications as VUV excited phosphors has been examined. The crystals were doped with lanthanide ions (Ce³⁺–Nd³⁺) with concentrations up to 100 at%. The self-quenching of luminescence is strongly reduced in this material. Luminescence spectra in the 50,000–10,000 cm⁻¹ range and excitation spectra in the 40,000–250,000 cm⁻¹ spectral range have been recorded at room and low temperature. Intense visible emission has been observed for Nd³⁺ and Pr³⁺. For the Pr³⁺ ions strong the ¹S₀–¹I₆ transition has been recorded only for concentrated crystals. Efficient conversion of VUV excitation to UV–VIS emission was observed in crystals doped with 3 and 100 at% of cerium. In both cerium-activated crystals the lifetimes of f–d transitions were equal to 32 ns.     

Perturbed Al photon echo ENDOR double resonance in Pr:YAlO3 and Eu:YAlO3

Aluminum pure quadrupole spectra measured by photon echo ENDOR double resonance (PENDOR) are reported for crystals of YAlO₃ doped with Pr³⁺ and for crystals doped with Eu³⁺. These spectra, which correspond to aluminum nuclei adjacent to a rare earth impurity, are compared to the results of a conventional NMR study of ²⁷ Al in YAlO₃.     

LiYF4:Pr3+能级晶场分裂链的计算

本文首次在稀土离子晶场光谱拟合中引进了唐敖庆等人的张量算符方法,从而获得了激光和上转换材料LiYF₄:Pr³⁺对应于晶场群链(R₃?T_d?D_2d?S₄)的能级分裂链,逐级晶场参量值和逐级近似波函数。这就为分析其有关空间电荷分布构形,讨论其光谱强度和其它光学、磁学、热力学性质等提供了逐级近似的依据。 关键词：     

掺杂晶体材料ZnGa_2O_4:Fe~(3+)局域结构畸变及其微观自旋哈密顿参量研究

基于Newman的晶场叠模型与微观自旋哈密顿理论,建立了ZnGa2O4:Fe3+晶体材料中磁性离子Fe3+局域结构与其自旋哈密顿(spin-Hamiltonian,SH)参量(包括二阶零场分裂(zero-field splitting,ZFS)参量D,四阶ZFS参量(a-F),Zeeman g因子:g//,g⊥,△g(=g//-g⊥))之间的定量关系.采用以全组态完全对角化方法为理论背景的CFA/MSH(Crystal Filed Analysis/Microscopic Spin Hamiltonian)研究软件,研究了ZnGa2O4:Fe3+材料中磁性离子Fe3+的SH参量与其局域结构的依赖关系.研究表明:对于ZnGa2O4:Fe3+晶体材料,当磁性离子Fe3+的局域结构畸变参数△R=0.0487 nm,△θ=0.192°时,其基态SH参量理论计算结果与实验测量符合很好,进一步表明Fe3+掺入晶体材料后将引起磁性Fe3+离子局域结构的微小畸变,但其仍然保持D3d点群对称局域结构.在此基础上研究分析了SH参量的微观起源,结果表明:ZnGa2O4:Fe3+晶体材料的SH参量主要来源于SO(spin-orbit)磁相互作用机理,来自其他磁相互作用机理(包括SS(spin-spin),SOO(spin-other-orbit),OO(orbit-orbit),SO-SS-SOO-OO)的贡献比较小.     

Energy Spectrum of YAG:Cr3+ and Thermal Shifts of Its R Lines

Traditional ligand-field theory has to be improved by taking into account both “pure electronic” contribution and electron-phonon interaction one (including lattice-vibrational relaxation energy). By means of improved ligand-field theory, R₁, R₂, R'₃, R'₂, and R'₁ lines, U band, ground-state zero-field-splitting (GSZFS) and ground-state g factors as well as thermal shifts of R₁ line and R₂ line of YAG:Cr³⁺ have been calculated. The results are in very good agreement with the experimental data. In contrast with ruby, the octahedron of ligand oxygen ions surrounding the central Cr³⁺ ion in YAG:Cr³⁺ is compressed along the [111] direction. Thus, for YAG:Cr³⁺ and ruby, the splitting of t₂³⁴A₂ (or t₂³²E) has opposite order, and the trigonal-field parameters of the two crystals have opposite signs. In thermal shifts of R₁ and R₂ lines of YAG:Cr³⁺, the temperature-dependent contributions due to EPI are dominant.