Na_2CaSiO_4:Sm~(3+),Eu~(3+)荧光粉的发光特性和能量传递

利用高温固相法合成Na_2CaSiO_4:Sm~(3+),Eu~(3+)系列荧光粉末,研究了Sm~(3+)和Eu~(3+)掺杂对Na_2CaSiO_4晶体结构的影响、材料发光特性以及存在的能量传递现象.X射线衍射结果表明Sm~(3+)和Eu~(3+)单掺及共掺样品均为单相的Na_2CaSiO_4结构,晶体结构没有改变.Na_2CaSiO_4:Sm~(3+)荧光样品在404 nm激发波长下呈现峰峰值为602 nm的橙红色荧光,来源于~4G_(5/2)→~6H_(7/2)跃迁.Na_2CaSiO_4:Eu~(3+)荧光样品在395 nm激发波长下发射出峰峰值为613 nm的红色荧光.对光谱和荧光寿命的测试和分析结果表明Sm~(3+)与Eu~(3+)之间存在能量传递,通过理论计算得到Sm~(3+)和Eu~(3+)之间的能量传递临界距离为1.36 nm,相互作用形式为电四极-电四极相互作用.随着Eu~(3+)掺杂浓度的增加,能量传递效率也逐渐提高至20.6%.     

Sm3+掺杂的SnNb2O6粉体的光谱特性

采用熔盐法制备了Sm³⁺掺杂的SnNb₂O₆粉体, 利用X射线粉末衍射、扫描电子显微镜对其物相和形貌进行了表征, 用激发、发射光谱和荧光寿命对样品的发光性能进行了研究.结果表明:所得样品为单斜晶系的SnNb₂O₆, 在407 nm的激发下, 有较强的橙红色发射, 最强峰位于599 nm, 属于Sm³⁺的⁴G_5/2→⁶H_7/2跃迁.     

Steady state and transient fluorescence studies of CaF2: Dy single crystals

The steady state and transient fluorescence spectra of CaF₂: Dy³⁺ have been studied using Ar⁺ and N₂ lasers in the temperature range 77–673 K and in the wavelength region 4500–9000 Å. The spectra show the presence of two types of centers (type A and type B) with decay times of 1.3 and 3.5 ms. The observed spectrum is mostly due to type A centers. Three new groups of fluorescence ⁴F_9/2−⁶H_11/2, ⁴F_9/2−(⁶H_9/2, ⁶F_11/2) and ⁴F_9/2−(⁶H_7/2, ⁶F_9/2) have been observed for type A centers, and a tentative assignment of the positions of the Stark levels of ⁶H_11/2, (⁶H_9/2, ⁶F_11/2) and (⁶H_7/2, ⁶F_9/2) has been made. The change in the intensity of the transitions with temperature and excitation wavelength are discussed.     

YNbO4：Tm3+/Yb3+上转换发光特性研究

按照50Nb₂O₅-（46-x）Y₂O₃-4Yb₂O₃-xTm₂O₃（x=0.1,0.2,0.5,1,2）的配比方式,采用高温固相法制备出了掺杂Tm³⁺/Yb³⁺的YNbO₄晶体粉末。在980 nm红外光激发下,观测到波长为478,645,707 nm的上转换荧光,分别对应于Tm³⁺离子的¹G₄→³H₆、¹G₄→³F₄、³F₃→³H₆能级跃迁过程。利用上转换发射功率与980 nm激光器工作电流关系估算出跃迁过程吸收光子数目为2.72,2.69,2.01,从而确定出前两者为三光子吸收过程,最后一个对应于双光子吸收过程。运用Judd-Ofelt理论研究样品光谱特性,根据样品的吸收谱得到样品的谱线强度参数Ω_t（t=2,4,6）,进而得出理论振子强度及实验振子强度,二者均方根偏差δ_rms=1.299×10^-7。计算了Tm³⁺离子向下能级跃迁的跃迁几率、跃迁分支比等参数。最后得出结论：（1）³F₄能级寿命较长,适合作为上转换中间能级;（2）³H₅能级寿命较长,且³H₅→³H₆跃迁分支比（96.46%）接近100%,可用于产生1 216 nm激光。     

On the luminescence of LiBaF3:Eu

From the temperature dependence of the line—band luminescence intensity ratio of LiBaF₃:Eu²⁺ a 4f−5d activation energy (Δ) of 800 cm⁻¹ is derived, being much higher than the value reported in the literature (100 cm⁻¹). The temperature dependence of the luminescence decay can be well described with Δ = 800 cm⁻¹ and with 4f−4f and 5d−4f radiative probabilities of 4×10²s⁻¹ and 6×10⁵s⁻¹, respectively.     

The transition probability of DJ-F0 and hole-burning quantum efficiency in the SryBa1−yFCl0.5Br0.5:Sm system

We report the changes of the ⁵D_J-⁷F₀(J = 2, 1, 0) transition probability with composition y and its effect on the hole burning quantum efficiency in the Sr_yBa_1−yFCl_0.5Br_0.5:Sm²⁺ system. We observed that the ⁵D_J-⁷F₀ transition probability increases with the increase of Sr concentration. This result is attributed to the reduction of the energy separation between the ⁵D_J level and the 4f5d bands, which makes the electron wave functions of ⁵D_J states mix further with that of the 4f5d states. The dependence of the hole-burning quantum efficiency on the 5D_J-⁷F₀ transition probability was derived by the dynamical equations of the spectral hole burning of divalent samarium. Furthermore, the hole-burning experiments in SrFCl_0.5Br_0.5:Sm²⁺ and BaFCl_0.5:Sm²⁺ were performed under the same conditions. The experimental results present that the hole-burning quantum efficiency of SrFCl_0.5Br_0.5:Sm²⁺ is higher than that of BaFCl_0.5Br_0.5:Sm²⁺.     

Ca3Y2Si3O12：Tm3+,Yb3+上转换发光粉的制备与发光性能研究

采用高温固相法成功制备了Ca₃Y₂Si₃O₁₂：Tm³⁺,Yb³⁺上转换蓝色发光材料。在980 nm 红外激光器激发下,发光粉呈现强烈的蓝光（475 nm）和近红外光（810 nm）以及较弱的红光（650 nm）发射,分别归因于Tm³⁺离子的¹G₄→³H₆、³H₄→³H₆和¹G₄→³F₄能级跃迁。随着Yb³⁺离子浓度的增加,发光粉上转换发射强度和发光亮度均呈现先增强后减弱的变化趋势。在最佳掺杂浓度下（Yb³⁺摩尔分数为15%）,蓝、红光强度分支比为12：1,色坐标为（0.129 2,0.152 3）。在3.9 W/cm²激发功率密度下,发光亮度可达6.8 cd/m²。上述结果证实,所制备发光粉呈现优异的蓝光上转换发射特性并具有潜在的应用价值。发光强度和激发光功率关系表明,所得上转换发射为三光子和双光子吸收过程。借助Tm-Yb体系能级结构详细讨论了上转换发射的跃迁机制。     

Electronic and vibronic spectra of Pr in LiYF4

The polarized absorption and fluorescence spectra of Pr³⁺ in single crystals of LiYF₄ having the scheelite structure have been investigated and assignments made on the basis of S₄ site symmetry. Strong vibronic coupling associated with the ³H₄→³H₅, ¹D₂ transitions in absorption and the ³P₀→³H_4,6 transitions in fluorescence was observed. Using selection rules for vibronic coupling and the known k = 0 phonons, these “extra” features of the spectrum can be accounted for in polarization and frequency.     

Tm-to-Ho resonant and nonresonant energy transfer in LiYF4

Absorption and luminescence measurements of Tm³⁺ and Ho³⁺ ions in LiYF₄:Tm³⁺, LiYF₄:Ho³⁺ and LiYF₄:Tm³⁺, Ho³⁺ crystals were carried out. The data collected were used to determine the Ho³⁺ absorption coefficient integral for ⁵I₈→⁵I₇ transition, and the overlap integral between the normalized Tm³⁺ luminescence spectrum due to the ³F₄→³H₆ transition and the Ho³⁺ absorption band due to ⁵I₈→⁵I₇ transition. The relevant critical transfer distance (R_o), that gives a measure of the Tm³⁺–Ho³⁺ coupling, was determined considering the Förster type interaction between the ions. It was found to be 22.5 Å and 28.8 Å at 300 and 78 K, respectively.     

稀土掺杂的NaGdF4上转换发光材料的合成与发光特性研究

采用水热法制备了一系列不同掺杂浓度的NaGdF₄:Re(Re=Tm³⁺,Er³⁺,Yb³⁺)上转换发光粉。通过X射线衍射(XRD)、电子扫描电镜(SEM)和上转换发射光谱对样品进行了表征。XRD研究结果表明:合成的样品均为六方结构NaGdF₄。估算的平均晶粒尺寸为41~43 nm。在980 nm红外光激发下,Er³⁺和Yb³⁺共掺杂的NaGdF₄发光粉发出分别来自于Er³⁺离子²H_{11/ 2},⁴S_3/2→⁴I_15/2跃迁的绿光和⁴F_9/2→⁴I_15/2跃迁的红光发射,Tm³⁺和Yb³⁺共掺杂的NaGdF₄发光粉发出分别来自Tm³⁺离子的¹G₄→³H₆跃迁的蓝光、¹G₄→³F₄和³F_2,3→³H₆跃迁的红光和³H₄→³H₆跃迁的近红外光发射。Er³⁺,Tm³⁺和Yb³⁺共掺杂的NaGdF₄发光粉的发光强度及红、绿、蓝光发射的相对强度受Yb³⁺离子掺杂浓度的影响。对样品中可能的上转换发光机制进行了讨论。计算的色坐标显示:可通过改变掺杂离子浓度对上转换发光的颜色进行调控。     

Optical absorption of isotopically enriched Li2B4O7 single crystals irradiated by thermal neutrons

Induced absorption spectra in the range 200–900 nm at 77 and 290 K for Li₂B₄O₇ single crystals, isotopically Li and B enriched are presented after irradiation of these crystals by thermal neutrons with fluence 1.8×10¹⁶ cm⁻². The dependence of induced absorption spectra on the isotope composition was revealed: for ⁶Li₂¹⁰B₄O₇ and ⁷Li₂¹⁰B₄O₇ crystals intensive band in the region of 280–294 nm was observed. Under substitution of ⁷Li isotope by ⁶Li in the lithium tetraborate lattice no changes in the absorption spectra were observed. The nuclear reaction ¹⁰B(n,)⁷Li is proposed to be the main mechanism of formation of the radiation defects.     

K5Bi0.9Er0.1(MoO4)4的晶体生长和光学性质

在化学计量的熔料里,用提拉法生长了K₅Bi_0.9Er_0.1(MoO₄)₄单晶。该晶体属于三方晶系,空间群为R3m,z=1.5,晶胞参数为a=6.029?,c=20.823?(六方表示)。晶体具有层状结构,沿着(0001)面容易解理。晶体在室温下的吸收光谱包括有若干条吸收带,它们是稀土离子所特有的。其中三个主要的吸收峰分别相当于从Er³⁺离子的基态 ⁴I_15/2向 ⁴G_11/2, ²H_11/2和 ⁴I_13/2能级的跃迁。本文还给出晶体中相当于 ⁴I_13/2→ ⁴I_15/2跃迁的荧光发射光谱。 关键词：     

Ba5SiO4Cl6: Yb3+, Er3+, Li+荧光粉的制备及上转换发光性质研究

本文采用高温固相反应法制备了Ba₅SiO₄Cl₆: Yb³⁺, Er³⁺, Li⁺ 荧光粉, 并对其上转换发光性质及其发光机理进行了研究. 在980 nm 激光的激发下, Ba₅SiO₄Cl₆: Yb³⁺, Er³⁺ 荧光粉呈现较强的红色(662 nm) 和较弱的绿色(550 nm) 的上转换发光, 红色和绿色的上转换发光分别对应于Er³⁺ 离子的⁴S_3/2/²H_11/2→⁴I_15/2 和⁴F_9/2→⁴I_15/2 跃迁, 且随着掺杂的Er³⁺ 和Yb³⁺ 离子浓度增加, 样品的上转换发光强度增加, 这是因为Yb³⁺ 离子和Er³⁺ 离子之间的能量传递效率增加引起的. 在0.5—0.8 W 功率激发下,样品属于双光子发射, 而在0.9—1.2 W 功率激发下样品具有新的上转换发光机理——光子雪崩效应. 探讨了Li⁺ 掺杂对Ba₅SiO₄Cl₆: Yb³⁺, Er³⁺ 样品的上转换发光性质的影响, Li⁺ 离子的掺杂引起Ba₅SiO₄Cl₆:Yb³⁺, Er³⁺ 上转换发光强度增加, 这是由于Li⁺ 离子的掺入降低了晶体场的对称性引起的.     

橙红色荧光粉Ca3Y2Si3O12：Sm3+的制备及发光特性

采用高温固相法在1 400 ℃下经二次煅烧合成了橙红色荧光粉Ca₃Y_2-xSi₃O₁₂：xSm³⁺,研究了Sm³⁺离子掺杂浓度及助熔剂对荧光粉发光性能的影响。XRD结果显示,所合成的荧光粉的主晶相为Ca₃Y₂Si₃O₁₂。荧光光谱分析表明,Ca₃Y₂Si₃O₁₂：Sm³⁺硅酸盐荧光粉可以在320~500 nm范围内得到有效激发,并发射橙红光。在402 nm激发下,样品发射光谱中的主发射峰分别位于562 nm（⁴G_5/2→⁶H_5/2）、598 nm（⁴G_5/2→⁶H_7/2）和646 nm（⁴G_5/2→⁶H_9/2）,其中598 nm处峰值最大。改变Sm³⁺离子掺杂浓度发现：荧光粉发光强度先增大后减小,最佳Sm³⁺掺杂量x（Sm³⁺）为5%,浓度猝灭机理为离子间的相互作用。讨论了几种助熔剂的影响,NH₄F、CaF₂和NaCl均降低荧光粉的发光强度,只有H₃BO₃能够显著增强样品的发光,其最佳掺杂质量分数为1%。     

近紫外光激发黄色荧光粉Ba3Y4O9：Dy3+的制备及发光特性

通过高温固相法合成了一系列Ba₃Y_4-xO₉：xDy³⁺荧光粉材料。利用X射线粉末衍射、荧光光谱和荧光寿命对样品进行了表征。实验表明,样品的激发光谱由一系列线状峰组成,峰值分别位于328,355,368,386,427,456,471 nm。在355 nm激发下,荧光粉在490 nm（⁴F_9/2→⁶H_15/2）和580 nm（⁴F_9/2→⁶H_13/2）处有很强的发射,发射光谱的色坐标位于黄光区域。研究了不同Dy³⁺掺杂浓度对样品发光性质的影响,发现样品的发光随着Dy³⁺浓度的增大而增强,但光谱形状基本保持不变,表明Dy³⁺占据了基质中低对称性的Y³⁺格位。当Dy³⁺摩尔分数x=0.08时出现发光强度猝灭现象,浓度猝灭机理为电偶极-电偶极相互作用。样品的发光寿命随着Dy³⁺浓度的增大逐渐减小,进一步证明了Dy³⁺离子之间存在着能量传递现象。Ba₃Y₄O₉：Dy³⁺荧光粉的发光位于黄光区域,有较好的热稳定性,是潜在的白光LED用荧光粉材料。     

LiNbO3和LiTaO3晶体Er3+/Yb3+掺杂水热外延层室温吸收光谱分析

本文引入与浓度和厚度有关的k_NL待定参数, 在J-O理论基础上, 对Er³⁺/Yb³⁺掺杂的LiNbO₃和LiTaO₃单晶衬底上 的多晶水热外延样品进行了基于吸收光谱的拟合计算. LiNbO₃:Ω₂=2.34× 10^-20 cm², Ω₄=0.77× 10^-20 cm², Ω₆=0.31×10^-20 cm², k_NL=4.32× 10^-2 mol·m^-2. LiTaO₃:Ω₂=1.68×10^-20 cm², Ω₄=0.84×10^-20 cm², Ω₆=0.45×10^-20 cm², k_NL=9.17×10^-3 mol· m^-2. 该方法可尝试推广到粉体或胶体等难以直接获得浓度和厚度数据的体系. 经上转换发光测试及光谱参数计分析认为Er³⁺/Yb³⁺离子的掺杂浓度比为1:1的情况下, 样品呈现绿色上转换发光光谱; 可尝试以降低基质声子能量的方法提高⁴I_13/2能级 对²H_11/2和⁴S_3/2能级的量子剪裁效率.     

上转换纳米粒子CaF2:Er3+,Yb3+的合成及其温敏特性

采用水热合成法制备了CaF₂：Yb³⁺,Er³⁺上转换纳米粒子。在980 nm激发下,研究了来源于Er³⁺的²H_11/2/⁴S_3/2→⁴I_15/2跃迁的绿光发射和来源于⁴F_9/2→⁴I_15/2跃迁的红光发射。由于Er³⁺具有一对热耦合能级（²H_11/2/⁴S_3/2）,所合成的样品在293~573 K温度范围内有良好的温敏特性。利用荧光强度比（FIR）技术,测得样品在483 K时具有最大灵敏度0.002 85 K^-1。     

The effect of zinc ions on the fluorescence spectra of (La, Zn)OF:Sm powder phosphors

This paper reports the fluorescence properties of a new series of (La, Zn) OF:Sm³⁺ powder phosphors. The measured fluorescence spectra were analyzed by computing the color coordinates and relative fluorescence intensity ratios (ED/MD). A bright yellowish-orange color was observed from these powder phosphors under a UV-source due to the confirmation of the transitions ⁴G_5/2→⁶H_5/2, ⁴G_5/2→⁶H_7/2, and ⁴G_5/2→⁶H_9/2. Scanning electron microscopic studies were performed to understand the average grain size of the synthesized powder phosphors.     

核壳纳米结构壳中Yb离子对稀土上转换发光温度特性的影响

采用油酸盐法分别制备出均匀的上转换发光裸核纳米粒子及其包覆具有不同Yb³⁺浓度掺杂的NaYF₄:Yb³⁺,Er³⁺核壳纳米结构的上转换纳米粒子。在不同温度下(90~450 K),研究分析了在壳中掺杂不同浓度Yb³⁺的NaYF₄:Yb³⁺,Er³⁺@NaYF₄:x%Yb³⁺核壳纳米体系的上转换发光特性。结果表明:在NaYF₄:Yb³⁺,Er³⁺上转换体系中,惰性壳中的525 nm(²H_11/2 →⁴I_15/2)发射峰呈现出与活性壳中不一样的趋势。壳层中掺杂的Yb³⁺通过声子对纳米粒子内部发光与表面及外界之间的相互作用起到了重要的"桥"连作用。     

Annihilation of the persistent luminescence of MAl2O4:Eu by Sm co-doping

The calcium aluminates doped with the Eu²⁺ and Nd³⁺ ions, CaAl₂O₄:Eu²⁺,Nd³⁺, are a novel and efficient persistent luminescence (i.e. afterglow) material. The Nd³⁺ ions were found to enhance the persistent luminescence. Some other R³⁺ co-dopants had similar or opposite, though weaker, effect. The Sm³⁺ (and Yb³⁺) ions suppressed almost completely the persistent luminescence and thermoluminescence of the Eu²⁺ ion. From the UV-excited luminescence and persistent luminescence spectra it was found that the Eu²⁺ ion acts as a luminescent centre with luminescence at the blue (λ_max=440 nm) region. The Sm³⁺ ion was reduced to the divalent state. The thermoluminescence glow curves of the CaAl₂O₄:Eu²⁺,Sm³⁺ material showed that the high-temperature glow peaks, i.e. deep traps, were suppressed almost completely. The Nd:YAG laser-excited high-resolution photoluminescence of the Sm²⁺ ion confirmed that the Eu²⁺ ion occupies only one Ca²⁺ site. Only weak perturbations were observed in the Sm²⁺ site due to the changes in the environment of the Sm²⁺ site.