Ce3+掺杂Li2O-MgO-Al2O3-SiO2玻璃的结构与荧光猝灭现象

采用熔融淬冷法制备了不同浓度Ce³⁺离子掺杂的20Li₂O-5MgO-20Al₂O₃-55SiO₂玻璃闪烁材料。采用X射线衍射(XRD)、高分辨透射电镜(HRTEM)技术、密度检测等方法研究了玻璃的微观结构随Ce³⁺离子掺杂浓度的变化规律, 采用荧光分光技术检测了玻璃的紫外光致激发光谱(PLE)、发射光谱(PE)。研究结果表明: 在不对称的晶体场作用下, Ce³⁺离子5d能级被劈裂为5个组分; 随着玻璃基质内Ce³⁺离子掺杂浓度增大, 玻璃的非晶化程度加深; 5d能级的劈裂宽度随之增大, 由此导致激发带向低能量端展宽、发射光谱明显红移; Ce³⁺离子的荧光发射强度随Ce³⁺离子掺杂浓度先升高、后降低, 浓度猝灭过程成为其荧光发射效率降低的主要原因。     

绿色长余辉发光材料MgGa2O4:Mn2+的制备及性能研究

采用高温固相法合成了MgGa₂O₄:xMn²⁺(x=0.5%,1%,3%,5%)系列绿色长余辉发光材料。通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、发光光谱、余辉光谱、热释光谱等表征手段对其长余辉发光性能进行了研究。样品的发射光谱的结果表明,Mn²⁺在509 nm处的特征发射峰,对应Mn²⁺离子的⁴T₁(⁴G)→⁶A₁(⁶S)电子跃迁,随着Mn²⁺掺杂浓度的增加,其发光强度先增强后减弱,掺杂浓度为3%时样品具有最好的发光性能;掺杂浓度为1%时其余辉强度最强,余辉时间可以持续1h以上;热释光谱在342 K附近出现一个宽峰,这表明样品存在大量的陷阱,这有利于捕获被激发的电子,形成长余辉发光。     

Lu2.94Al5O12:0.06Ce3+绿色荧光粉的制备及光致发光

采用高温固相法制备了Lu_2.94Al₅O₁₂:0.06Ce³⁺绿色荧光粉。通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)和光致发光光谱(PL)对样品的物相、形貌及发光性能进行了表征。结果表明,所合成的Lu_2.94Al₅O₁₂:0.06Ce³⁺绿色荧光粉为立方晶系,表面为类球形。激发光谱中,位于340和450 nm的激发峰分别归属于4f的两个能级到5d能级的跃迁而产生的吸收,340 nm处的激发峰是由于发光是由于²F_5/2到5d的跃迁,而450nm处的激发峰是由于²F_7/2到5d的跃迁。发射光谱中,位于525 nm的发射峰对应Ce³⁺的4f-5d电子跃迁。当Ce₃₊掺杂量为6%,1500℃煅烧5 h时,Lu_2.94Al₅O₁₂:0.06Ce³⁺绿色荧光粉CIE色坐标为(0.3683,0.5959),是一种可以用作白光LED的绿色荧光粉。     

8YSZ/Y3Al5O12:Ce3+光敏复合热障涂层的等温氧化及光谱响应特性

为了监测热障涂层在氧化过程中陶瓷层内部的残余热应力,制备了Y₃Al₅O₁₂:Ce³⁺含量不同的8YSZ/Y₃Al₅O₁₂:Ce³⁺光敏复合热障涂层。研究了Y₃Al₅O₁₂:Ce³⁺不同含量下8YSZ/Y₃Al₅O₁₂:Ce³⁺光敏复合热障涂层等温氧化过程的失效机理,阐述了陶瓷层内部残余热应力与Y₃Al₅O₁₂:Ce³⁺的发射光谱的峰值波长之间的内在响应机制;同时研究了8YSZ/Y₃Al₅O₁₂:Ce³⁺光敏复合热障涂层陶瓷层发射光谱峰值波长偏移量与氧化时间的关系,并拟...     

CaF2:20Yb2Er/Na@CaF2:Ce纳米材料近红外二区发光性能研究

利用热分解法制备了CaF₂:20Yb2Er/Na@CaF₂:Ce纳米颗粒，并对其NIR-Ⅱ发光性能和荧光寿命进行了探讨。研究结果表明，在980 nm光源激发下，其NIR-Ⅱ发光性能强度约为CaF₂:20Yb2Er的68倍，且位于1 525 nm处的荧光寿命为2.29 ms。该体系Yb³⁺作为敏化剂，Er³⁺作为激活剂，Na⁺共掺杂使晶体场的局部对称性改变，核壳结构的构建使发光中心的荧光猝灭最小化，壳层结构引入Ce³⁺可以使得Er³⁺与Ce³⁺在界面处产生交叉弛豫。由此可见，将离子共掺杂和构建核壳结构两种策略结合起来更有利于NIR-Ⅱ发光性能的提升。综上，CaF₂:20Yb2Er/Na@CaF₂:Ce纳米颗粒在生物成像领域具有潜在的应用价值。     

黄色荧光粉La3Si6N11∶Ce3+的结构、性能研究及第一性原理计算

运用高温固相法合成掺铈的氮化物荧光粉La₃Si₆N₁₁∶Ce³⁺。采用X射线衍射仪、能谱仪、荧光光谱仪对合成样品的结构、发光性能等进行研究，利用Rietveld方法对其结构精修，并计算了La₃Si₆N₁₁∶Ce³⁺的色坐标、色纯度和色温。结果表明：该荧光粉的色坐标为(0.4165,0.558),落在黄绿光区域，计算得到La_2.82Si₆N₁₁∶Ce_0.18³⁺的色纯度约为92.86%,具有较高的纯度，相关色温为4137K,属于中间色温。通过计算可得掺杂后La₃Si₆N₁₁∶Ce³⁺的带隙值为2.92eV,相对掺杂前略微减少，且La₃Si₆N₁₁∶Ce     

Ce:YAG荧光陶瓷掺杂Gd对白光LED发光性能的影响

Ce: YAG荧光陶瓷具有突出的导热性及化学稳定性, 相比有机硅胶封装法在高功率白光LED的应用上具有更广阔的应用前景。本研究采用真空固相烧结法制备了不同Gd掺杂浓度的(Gd, Y)₃Al₅O₁₂:Ce样品, 通过XRD, SEM及荧光光谱等表征手段, 研究了Gd掺杂对Ce:YAG荧光陶瓷的晶体结构及其用于白光LED时对发光性能的影响。实验表明, 随着Gd掺杂浓度的提高, Gd³⁺取代Y³⁺ 的位置进入晶格, 使得样品的晶格常数增加。Gd³⁺还影响了Ce³⁺对蓝光的吸收, 同时Ce³⁺将蓝光转换成黄光的效率也下降, 导致光效从81.45 lm/W降低至63.70 lm/W。Gd的掺 杂使Ce³⁺的光致发光谱峰位从534 nm向564 nm红移, 显色指数从61.3提升至70.2。Gd的掺杂虽然降低了发光 效率, 但显著提高了(Gd, Y)₃Al₅O₁₂:Ce样品的显色指数, 使得黄色YAG荧光陶瓷应用于白光LED的性能得到了 提高。     

Mg共掺杂Gd3(Al,Ga)5O12:Ce晶体快发光的作用机理

Gd₃(Al,Ga)₅O₁₂:Ce (GAGG:Ce)闪烁体综合性能优异, 应用前景广阔。为加快GAGG的发光衰减速度, 本研究通过提拉法生长了Mg共掺的Gd₃(Al,Ga)₅O₁₂:Ce单晶。测试结果显示, 随着Mg²⁺掺杂浓度增加, 晶体的闪烁衰减速度加快, 光输出降低。传统解释认为, Mg²⁺通过电荷补偿作用将部分Ce³⁺转换成Ce⁴⁺, 后者的发光速度更快。本研究尝试从缺陷的形成与抑制的角度来讨论Mg改善GAGG:Ce晶体闪烁性能的作用机理。由于Ce的离子半径比Gd大, Ce离子掺入将导致发光中心Ce_Gd附近的晶格发生畸变。畸变结果为近邻的八面体格位空间变大, 反位缺陷将更容易在这些变大的八面体格位形成。最终每个发光中心Ce_Gd被四个反位缺陷Gd_Al包裹, 后者捕获载流子, 延缓从基体到发光中心的能量传递, 导致发光速度变慢。由于Mg的离子半径介于Gd和Al之间, Mg_Al将更容易在上述畸变的八面体格位形成, 这会抑制反位缺陷Gd_Al在发光中心Ce_Gd附近形成(或富集), 最终降低(甚至消除)反位缺陷对发光中心的不良影响。XEL测试结果显示, 随着Mg掺杂量增大, 与反位缺陷相关的发射峰强度变弱, 这可以证明Mg对反位缺陷有抑制作用。     

Ce3+-Tb3+共掺杂黄磷炉渣微晶玻璃的发光与能量传递

以黄磷炉渣为原料,采用高温熔融法制备Ce³⁺-Tb³⁺共掺杂黄磷炉渣发光微晶玻璃,通过差热分析(DTA)、X射线衍射(XRD)、稳态/瞬态荧光(FLS)、CIE色度等探究不同的Tb³⁺掺杂量对微晶玻璃析出晶相、发光性能和样品色度的影响。结果表明,Ce³⁺和Tb³⁺的引入,微晶玻璃主晶相为硅灰石,在310 nm波长激发下,随着Tb³⁺掺杂量增加,位于380 nm处Ce³⁺的特征发射峰减小,543 nm处Tb³⁺的特征发射峰增强,证实Ce³⁺和Tb³⁺之间存在能量传递,能量传递效率达到24.55%。此外,通过调整Tb³⁺掺杂量,微晶玻璃发光颜色可由蓝光调至绿光,从而实现发光颜色的可控化。     

Y3+掺杂Ce:Li6Lu(BO3)3闪烁体的发光性能研究

针对Ce:Li₆Lu(BO₃)₃晶体有效原子序数(Z_eff)高的问题, 采用低原子序数的Y³⁺离子部分置换晶体中的Lu³⁺离子。通过固相合成法制备了Ce:Li₆Lu_1-xY_x(BO₃)₃(0≤x≤1)固溶体。X射线粉末衍射(XRD)分析表明, 该系列固溶体结构与Li₆Gd(BO₃)₃晶体相同, 空间群为P2_1/c。其X射线激发发射(XSL)的发光强度随着Y³⁺的含量增加而降低, 当x=0.5时, 固溶体的有效原子序数与Li₆Gd(BO₃)₃闪烁体相当, 但XSL发光强度是其1.4倍。Ce:Li₆Lu_0.5Y_0.5(BO₃)₃的XSL光谱和PL光谱都在400 nm附近出现Ce³⁺离子的特征峰, 可拟合出361和419 nm两个发光分量, 分别对应于Ce³⁺离子的激发态电子的⁵d₁→²F_5/2和⁵d₁→²F_7/2能级跃迁。Ce:Li₆Lu_0.5Y_0.5(BO₃)₃固溶体的衰减时间比Ce:Li₆Lu(BO₃)₃略长, 为19.6 ns。当x=0.50~0.70时, Ce:Li₆Lu_1-xY_x(BO₃)₃(0≤x≤1)闪烁体比较适合作为中子探测材料。     

Influence of additional Eu coactivator on the luminescence properties of Tb3Al5O12:Ce, Eu

The luminescence properties of doubly activated terbium aluminium garnet samples were investigated in the present study. Commercial Tb₃Al₅O₁₂:Ce³⁺ (TAG:Ce) shows the typical Ce³⁺ ion luminescence of the allowed Ce³⁺ d–f transition. Eu³⁺ co-doping, however, reveals interesting results. In TAG:Ce, Eu, both Ce³⁺ and Eu³⁺ luminescence was measured at different Ce and Eu activator concentrations. The Ce³⁺ ion can be used as a sensitizer in the TAG lattice that transfers its energy directly or via the Tb sublattice to the activator Eu³⁺. The energy-level diagram was proposed to explain the luminescence mechanism. Application of TAG:Ce, Eu with improved chromaticity coordinates CIE (Commission Internationale de l’Eclairage) and color rendering index (CRI) in light emitting diodes (LEDs) is demonstrated.     

Synthesis and spectral properties of Ce[Ag(CN)2]3

Cerium ion luminescence in crystalline hosts forms the basis of many blue phosphor and scintillator technologies. We report the synthesis of luminescent single crystals of cerium dicyanoargentate. The luminescence properties are characterized using both steady-state and time-resolved spectroscopy. The broad, overlapping dicyanoargentate and Ce³⁺ emissions are decomposed into three Gaussians, revealing the characteristic dicyanoargentate emission at 350 nm while the Ce³⁺ 5d–4f transitions are observed at 359 nm and 391 nm. Excitation measurements show that the 4f–5d Ce³⁺ absorption overlaps the 320 nm emission of the dicyanoargentate ions, leading to a strong coupling between the dicyanoargentate energy donors and Ce³⁺ acceptors. We conclude that the cerium is excited through an energy transfer process from the dicyanoargentate species, resulting in strong room temperature luminescence.     

Enhancement of Er I13/2 population in Y2O3 by energy transfer to Ce

We report measurements of the energy transfer between Er³⁺ and Ce³⁺ in Y₂O₃. The transition between the Er^{3+ 4}I_11/2 and ⁴I_13/2 excited states can be stimulated by energy transfer to Ce³⁺, augmenting the population in the ⁴I_13/2 state at the expense of that in the ⁴I_11/2 state. Experiments were performed on Y₂O₃ planar waveguides doped with 0.2 at.% erbium and 0–0.42 at.% cerium by ion implantation. From measurements of Er³⁺ decay rates as a function of cerium concentration we derive an energy transfer rate constant of 1.3×10⁻¹⁸ cm³/s. The efficiency of the energy transfer amounts to 0.47 at 0.42 at.% cerium. The energy transfer rate constant measured in Y₂O₃ is two times smaller for Er³⁺→Ce³⁺ than that for Er³⁺→Eu³⁺ in the same material.     

Controllable formation of Er–Yb codoped Al2O3 films by the non-aqueous sol–gel method

1 mol%Er³⁺–10 mol%Yb³⁺ codoped Al₂O₃ thin films have been prepared on thermally oxidized SiO₂/Si(110) substrates by a dip-coating process in the non-aqueous sol–gel method from the hydrolysis of aluminum isopropoxide [Al(OC₃H₇)₃] under isopropanol environment. Addition of N,N-dimethylformamide (DMF) as a drying control chemical additive (DCCA) into the sol suppresses formation of the cracks in the Er³⁺–Yb³⁺ codoped Al₂O₃ thin films when the rare-earth ion is doped with a high doping concentration. Homogeneous, smooth and crack-free Er³⁺–Yb³⁺ codoped Al₂O₃ thin films form at the conditions by a molar ratio of 1:1 for DMF:Al(OC₃H₇)₃. A strong photoluminescence spectrum with a broadband extending from 1.400 to 1.700 µm centered at 1.533 µm is obtained for the Er³⁺–Yb³⁺ codoped Al₂O₃ thin films, which is unrelated to the addition of DMF. Controllable formation of the Er³⁺–Yb³⁺ codoped Al₂O₃ thin films may be explained by the fact that the DMF assisted the deprotonation process of Al–OH at the surfaces of gel particles, resulting in enhancement of the degree of polymerization of sols and improvement of the mechanical properties of gel thin films.     

Long lasting phosphorescence of Sr4Al14O25:Eu,Dy thin films by magnetron sputtering

This paper reports the preparation process and the long lasting phosphorescence of the Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ thin films obtained by magnetron sputtering. Phosphorescence was achieved by annealing the films in reducing atmosphere. Sr₄Al₁₄O₂₅ thin film was obtained when the films were treated at 1200 °C, while SrAl₂O₄ was generated as the intermediate phase during the annealing process. Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ film generated an emission at 485 nm, and SrAl₂O₄:Eu²⁺,Dy³⁺ film showed an emission peaking at 515 nm. Afterglow characteristics were observed for both films, and Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ film showed a better afterglow property than the SrAl₂O₄:Eu²⁺,Dy³⁺ film due to a deeper trap level and a higher trap concentration formed in the thin films.     

高功率激光照明用Al2O3-YAG:Ce复相陶瓷荧光体的组分设计与性能优化

结合蓝色激光二极管和黄色荧光转换器制备的固态激光照明引起了人们极大的关注, 但荧光转换材料的热猝灭效应显著影响了高功率激光照明的实现。通过组分设计和性能优化可以提高荧光转换器的热导率和发光均匀性。本工作采用固相反应烧结技术制备了一系列不同Al₂O₃含量的Al₂O₃-YAG:Ce复相陶瓷荧光体, 研究了Al₂O₃含量对Al₂O₃-YAG:Ce陶瓷荧光体微观结构、相组成、光学性能和热学性能的影响。Al₂O₃-YAG:Ce陶瓷荧光体在800 nm处的总透过率随着Al₂O₃含量的增加(0→90%)而下降(82.6%→23.6%)。Al₂O₃-YAG:Ce陶瓷荧光体的激发和发射强度随Al₂O₃含量的增加先增大后减小。当Al₂O₃/Al₂O₃-YAG:Ce的质量比为70%时, 陶瓷荧光体在室温下的热导率高达25.7 W·m^-1·K^-1, 且表现出最高的发射强度。当采用功率密度为20 W·mm^-2的蓝光二极管泵浦 70% Al₂O₃-YAG:Ce复相陶瓷荧光体时, 可获得3724 lm的高光通量和239.4 lm·W^-1的高流明效率。此外, 当功率密度从1 W·mm^-2增大到20 W·mm^-2时, 流明效率仅下降10.5%, 光通量持续增加且未出现发光饱和。上述结果显示, Al₂O₃-YAG:Ce复相陶瓷荧光体具有良好的发光效率和热稳定性, 将在高功率激光照明中具有广阔的应用前景。     

Synthesis, structure and luminescent properties of Lu(PO3)3

A new structural type of rare earth metaphosphate, Lu(PO₃)₃, was prepared from high-temperature solution, of which the crystal structure was solved in S.G. of Cc (No.9) and Z = 4 with unit cell dimensions of a = 13.972(3) Å, b = 6.6710(13) Å, c = 9.958(2) Å and β = 127.36(3)°. In Lu(PO₃)₃, [LuO₆] octahedra connect with the non-bridging oxygens on (PO₃)_n infinite zigzag chains that extended along c-axis. The VUV and X-ray excited luminescent properties of undoped and Ln³⁺ (Ln = Ce, Eu, Tb) doped samples were examined, from which the optical band gap was estimated to be 8.3 eV. Besides, in the undoped sample a STE emission within 320–480 nm was observed, which probably be related to oxygen defects. However, in the Lu(PO₃)₃:Ce sample the Ce³⁺ emission was weak and STE emission was totally quenched under hard X-ray excitation.