On-line induced absorption measurement on PbWO4, YAlO3:Ce and CsI scintillating crystals

On-line measured radiation-induced absorption spectra and their kinetics are presented for the doped PbWO₄, YAlO₃:Ce and CsI crystals. In the doubly doped PbWO₄:Mo,Y crystals the saturation level of the induced absorption increased with Mo concentration up to 2750 ppm. With a higher concentration it again gradually decreased. Yttrium co-doping around 100 ppm improved considerably the radiation hardness of Mo-doped PbWO₄. Characteristic recovery time of these crystals was about 30 min. Positive influence of Zr⁺⁴ co-doping on characteristics of a set of YAlO₃:Ce samples resulted in decrease in the induced absorption intensity. The presence of very slow recovery processes was in good agreement with thermoluminescence characteristics above room temperature reported earlier. An absorption band round 420 nm appeared in as-grown CsI crystals doped with Tl, and was related to the oxygen contamination.     

Radiation-stimulated defects into LaB3O6 and Li6Gd(BO3)3:Ce single crystals

The radiation-induced defect types in LaB₃O₆ and Li₆Gd(BO₃)₃:Ce single crystals have been determined taking into account crystal-lattice features, absorption characteristics, photo- and thermostimulated luminescence data. The possible activator center models in Li₆Gd(BO₃)₃:Ce crystals are proposed.     

X-ray damage characterization in BaLiF3,KMgF3 and LiCaAlF6 complex fluorides

Two-inch sized KMgF₃,BaLiF₃ and LiCaAlF₆ (LiCAF) single crystals were grown by the Czochralski method under a CF₄ atmosphere. X-ray irradiation was used to carry out a comparative study of induced optical absorption phenomena and colour centre creation in the ultra-violet and visible spectral regions. The integral of the induced absorption spectra is significantly lower in LiCAF with respect to the other studied materials. It is found that the amplitude of the F-absorption band is suppressed more than a factor of 3 by Mg-doping. For Mg-doped crystals, the optimum doping concentration is about 0.2 mol% of Mg²⁺.     

Gd3(Al,Ga)5O12:Ce闪烁晶体缺陷对其发光性能的影响

新型闪烁晶体Gd₃(Al,Ga)₅O₁₂:Ce(GAGG:Ce)在制备过程中易出现包裹体及反格位缺陷等问题,严重影响晶体的性能.为了抑制这些缺陷以得到大尺寸高质量的GAGG:Ce晶体,本文以Gd₃(Al,Ga)₅O₁₂为基质、Ce3+为掺杂离子,采用提拉法生长得到了GAGG:Ce晶体,并对不同晶体部位的物相结构、微区成分、透光性质、发光及时间性能进行了测试和对比分析.结果表明,GAGG:Ce晶体的透过谱中存在340和440 nm两处Ce³⁺特征吸收带,且位于550 nm处的直线透过率为82%.晶体尾部因杂相包裹体等宏观缺陷的影响,导致其透过率下降至70%左右.微区成分分析进一步表明GAGG:Ce晶体中存在三种类型的包裹体,分别为富Gd相、富Ce相及(Al,Ga)₂O₃相.GAGG:Ce晶体的X射线激发发射谱中在550 nm附近存在Ce³⁺宽发射带,且380 nm处还存在GdAl/Ga反格位缺陷引起的发射.晶体中存在的杂相包裹体及GdAl/Ga反格位缺陷等因素导致Ce³⁺在GAGG基质的发光强度下降12.5%;GdAl/Ga反格位离子与近邻Ce的隧穿效应使得GAGG:Ce晶体的衰减时间由117.7 ns延长至121.9 ns,且慢分量比例由16%增加至17.2%.     

Ba9Y2(SiO4)6: Ce3+,Mn2+荧光粉的发光特性及能量传递

利用高温固相法制备了Ba₉Y₂(SiO₄)₆:Ce³⁺,Mn²⁺(BYS:Ce³⁺,Mn²⁺)荧光粉,并通过X射线衍射(XRD)谱、激发和发射光谱及荧光寿命的测试对材料的结构、发光特性和能量传递进行了研究。在327 nm激发下,BYS:Ce³⁺,Mn²⁺发射光谱中包含2个发射峰,分别为位于407 nm的Ce³⁺的蓝紫光发射和位于597 nm的Mn²⁺的红光发射。在该体系中,发现了Ce³⁺向Mn²⁺的有效能量传递,使得Mn²⁺在597 nm处的红光发射显著提高,当x(Mn²⁺)=0.25时,BYS:Ce³⁺,xMn²⁺的能量传递效率可达39%。实验表明,该荧光粉可为紫外基白光LED提供良好的红光光源。     

Ce3+和Mn2+掺杂的Ba9(Y2-xScx)(SiO4)6光谱特性和温度特性研究

采用高温固相法制备了Ba₉(Y_2-xSc_x)(SiO₄)₆:Ce³⁺,Mn²⁺(x=0,0.5,1.0,1.5,2.0)样品。在该体系中,当Sc³⁺含量从x=0逐渐增加至x=2时,Ce³⁺的蓝光发射强度提高了1.7倍;同时,Mn²⁺的红光发射强度提高了1.9倍,显示了优良的红光特性。样品的发射光谱和漫反射光谱表明,Ce³⁺、Mn²⁺发射强度的增加与Ce³⁺吸收能力和Ce³⁺向Mn²⁺能量传递的提升有直接关系。研究了样品Ba₉Sc₂(SiO₄)₆:Ce³⁺,Mn²⁺的热稳定性。随着温度的升高,Mn²⁺的红光发射呈现先升后降的态势。当温度从室温升至488 K时,Mn²⁺发射强度仅下降至室温时的84%,表现出优良的热稳定性。高亮的红光发射和优良的热稳定性表明该荧光材料可为紫外基白光LED提供良好的红色光源。     

Ce和O空位共掺杂TiO_2的电子结构与光学性质

采用基于密度泛函理论加U的计算方法,研究了Ce和O空位单(共)掺杂锐钛矿相TiO_2的电子结构和光吸收性质.计算结果表明,Ce和O空位共掺杂TiO_2的带隙中出现了杂质能级,且带隙窄化为2.67 eV,明显比纯TiO_2和Ce,O空位单掺杂TiO_2的要小,因而可提高TiO_2对可见光的响应能力,使TiO_2的光吸收范围增加.光吸收谱显示,掺杂后TiO_2的光吸收边发生了显著红移;在400.0—677.1 nm的可见光区,共掺杂体系的光吸收强度显著高于纯TiO_2和Ce单掺杂TiO_2,而略低于O空位单掺杂TiO_2.此外,Ce掺杂TiO_2中引入O空位后,TiO_2的导带边从-0.27 eV变化为-0.32 eV,这表明TiO_2的导带边的还原能力得到了加强.计算结果为Ce和O空位共掺杂TiO_2在可见光光解水方面的进一步研究提供了有力的理论依据.     

MSO4:Eu2+(M =Mg,Ca, Sr,Ba)的等电子陷阱与热释光特性

在硫酸盐掺入稀土元素的研究中, 得到了几种掺入Eu²⁺的碱土金属硫酸盐磷光体MSO₄:Eu²⁺ (M =Mg, Ca, Sr, Ba), 这组磷光体具有与掺入三价稀土离子(Tm³⁺, Dy³⁺, Eu³⁺)的碱土金属硫酸盐截然不同的热释光特性, 热释光三维发光谱中只呈现一个热释光峰, 对γ和βup辐射的热释光剂量响应为线性-亚线性响应. 结果清楚地显现出Eu²⁺对碱土金属阳离子的等价取代而形成的等电子陷阱对这些磷光体的热释光特性起了关键性的作用, Eu²⁺等电子陷阱与基质中的本征缺陷SO₄^2-形成的缺陷复合体作为热释光多阶段过程的基本作用单元, 基本上产生一次作用热释光事件. SrSO₄:Eu²⁺是一种典型的等电子陷阱发光的磷光体, 它具有相当高的热释光和光释光发光效率.     

LiMAlF6(M=Ca,Sr)基质中Ce3+、Eu3+、Tb3+的光谱研究

合成了Ce³⁺、Eu³⁺、Tb³⁺激活的LiMAlF₆(M=Ca,Sr)磷光体,研究了它们的光谱特性.观察到稀土离子在LiCaAlF₆和LiSrAlF₆中的光谱十分相似.这与它们所处的晶场环境相同有关.发现Ce³⁺在此基质中有较弱的330nm发射,这一Ce³⁺的发光中心可用于作为材料质量的评价.     

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.     

Luminescence and OSL study of the inorganic compounds Tl-doped (NH4)2BeF4 and (NH4)2SiF6

The search of materials with efficient optically stimulated luminescence (OSL) properties and a high hydrogen content for fast neutron dosimetry has led to the development of Tl⁺-doped ammonium salts (NH₄)₂SiF₆ and (NH₄)₂BeF₄. Preliminary OSL studies have shown that the OSL in (NH₄)₂SiF₆:Tl⁺ and (NH₄)₂BeF₄:Tl⁺is efficient. In order to optimise the OSL emission and its detection, the identification of the luminescent centres in the OSL process is necessary. This study focuses on the identification of the luminescent centres associated with Tl⁺ based on optical studies in the vacuum UV (VUV) at different temperatures.     

金属离子掺杂的Lu2Si2O7的第一性原理研究

焦硅酸镥掺铈(LPS:Ce)具有突出的闪烁性能, 比如高光产额和快衰减, 但晶格中的氧空位会影响其闪烁性能. 本文通过第一性原理方法研究了Li, Na, Mg和Ca在LPS中的稳定性和对氧空位的影响. 结果表明: 在缺氧环境下, 这些离子倾向于占据间隙位, 从而可能抑制氧空位. 分析了杂质离子对LPS电子结构的影响. 关键词： 第一性原理 焦硅酸镥 杂质缺陷     

Effects of Ce3+ energy level structure on absorption and luminescence properties of Ce-doped YAlO3,Y3Al5O12,and LaAlO3 single crystals

We investigate the spectra and scintillation properties of Ce:YA103,Ce:Y₃Al₅O₁₂,and Ce:LaA103.For Ce:YAlO₃,the excitation spectrum is very similar with the absorption spectrum;for Ce:Y₃Al₅O₁₂ and Ce:LaAlO₃,the excitation spectra are different from the absorption spectra.Further,Ce:YAlO₃ has better scintillation performance than Ce:Y₃Al₅O₁₂ whereas Ce:LaAlO₃ has not demonstrated scintillation performance to date.We also provide reasonable explanations for these experimental phenomena from the viewpoint of energy level structure.     

红色荧光粉Na8.33 La1.67(SiO4)6 O2:Eu3+的制备及发光特性

采用高温固相法制备了Na_(8. 33)La_(1. 67)(SiO_4)_6O_2∶Eu~(3+)红色发光材料,利用X射线衍射仪测定其晶体结构,利用Hitachi F4600表征其发光光谱。在紫外光激发下,样品Na_(8. 33)La_(1. 67)(SiO_4)_6O_2∶Eu~(3+)呈多峰发射,分别对应于Eu~(3+)的~5D_0-~7F_j(j=0,1,2,3,4)能级跃迁,主峰是位于615 nm的~5D_0-~7F_2跃迁发射。研究了Eu~(3+)掺杂浓度对材料发光性质的影响,改变Eu~(3+)掺杂浓度,样品的发射强度随之改变,Na_(8. 33)La_(1. 67)(SiO_4)_6O_2∶Eu~(3+)材料的Eu~(3+)浓度为15%时,发光强度最大。讨论了浓度猝灭的机理,理论计算表明引起Eu~(3+)离子能量弥散的主要原因是离子间交换相互作用。     

Evaluation of Ce3+ and alkali metal ions Co-doped LiSrAlF6 crystalline scintillators

High scintillation efficiency of Eu-doped LiSrAlF₆ (LiSAF) and LiCaAlF₆ (LiCAF) codoped with alkali metal ions has been reported in our recent studies. Thus in this paper, we demonstrated the scintillation properties of 1% Ce-doped LiSAF crystals with 1% alkali metal ions co-doping to increase the light yield and understand the scintillation mechanism. The crystals showed intense emission band corresponding to the 5d-4f transition of Ce³⁺, and their light yields under thermal neutron excitation were higher than that of the Ce only doped crystal. Especially, the light yield of Ce–Na co-doped crystal exceeded about two times that of Ce only doped one.     

Ba3WO6:Eu3+红色荧光粉的结构及其发光特性

以高温固相法成功合成了一系列Eu³⁺离子激活Ba₃WO₆红色荧光粉。分别采用X射线衍射（XRD）和荧光光谱（FL）对样品的晶体结构和发光性能进行了表征。结果表明,样品均具有立方晶系的双钙钛矿结构;Eu³⁺离子的激发谱由一个宽带（包括Eu³⁺-O^2-和W⁶⁺-O^2-电荷转移带）和若干个窄峰（4f-4f电子跃迁）组成,而跃迁⁵D₀→⁷F₁和⁵D₀→⁷F₂则构成了发射谱的主要部分。调整原材料中BaCO₃和WO₃的量的比,XRD的主衍射峰位发生红移至与标准谱完全吻合,发光强度有所提升并分析了原因。Eu³⁺离子的临界摩尔分数为0.05,临界距离（R_c）为1.263 4 nm。在314 nm或394 nm激发光下,样品发出红光（λ_max=596 nm）,色坐标为（0.618,0.342）,在LED照明、显示等领域具备一定潜力。     

YAG：Ce发光材料合成的助熔剂研究

采用高温固相法合成YAG:Ce荧光粉时,传统的以硼酸为助熔剂的产物硬度很大,处理过程中容易破坏晶体形貌,影响发光性能.采用氟化物助熔剂(MgF₂、CaF₂、SrF₂、BaF₂、AlF₃)及它们与H₃BO₃混合助熔剂来制备YAG:Ce,研究了助熔剂种类及其浓度对制得的粉体发光性能的影响,比较了它们的晶体形貌与物相组成.结果表明,采用不同助熔剂合成的YAG:Ce的激发光谱及发射光谱基本相同,而BaF₂、AlF₃、SrF₂及它们与H₃BO₃的混合助熔剂系列,可在一定程度上降低产品硬度、提高产品发光亮度;其中H₃BO₃~SrF₂系列、H₃BO₃~BaF₂系列的晶化程度与粒度分布均有改善;H₃BO₃~BaF₂系列的物相组成比较纯,除Y₃Al₅O₁₂主相外基本无杂相.     

2018年6期 电子期刊

研究了白光LED用K₂SiF₆：Mn⁴⁺红色荧光粉湿热环境下的发光性能劣化规律及机理。结果表明,环境中水汽的侵蚀可导致K₂SiF₆：Mn⁴⁺荧光粉发光性能劣化,且温度升高可加剧该劣化过程。85%湿度/70℃下处理6 h,K₂SiF₆：7%Mn⁴⁺荧光粉相对亮度降至初始值的25%。荧光粉中Mn⁴⁺含量越高,湿热条件下的性能劣化越显著。基于湿热处理前后荧光粉的XRD、表面形貌以及光学性能的对比分析,发现湿热环境下K₂SiF₆：Mn⁴⁺荧光粉的劣化主要是由于表面水汽侵蚀产物强吸收400~700 nm的可见光,降低荧光粉的激发效率以及再吸收荧光粉的发射光。水热后处理可使K₂SiF₆：Mn⁴⁺荧光粉颗粒尺寸增大,结晶性提高,从而显著改善其耐水性。85%湿度/70℃下处理6 h,水热后处理K₂SiF₆：7%Mn⁴⁺荧光粉的相对亮度仍可保持初始值的80%。     

Structure and optical damage resistance of near-stoichiometric Zn:Fe:LiNbO3 crystals

A series of near-stoichiometric Zn:Fe:LiNbO₃ crystals were grown by the high-temperature top-seed solution growth (HTTSSG) method from stoichiometric melts doped with 6 mol% K₂O. Infrared (IR) transmission spectra were measured and discussed in terms of the defect structure of the near-stoichiometric Zn:Fe:LiNbO₃ crystals. The results of the transmitted beam pattern distortion method show that the optical damage resistance of the near-stoichiometric Zn:Fe:LiNbO₃ crystals increases rapidly when the ZnO concentration exceeds a threshold value. The threshold value concentration of ZnO of the near-stoichiometric Zn:Fe:LiNbO₃ crystals is much lower than that of the congruent LiNbO₃ crystals. The dependence of the optical damage resistance on the defect structure of the near-stoichiometric Zn:Fe:LiNbO₃ crystals are discussed, and the holographic recording properties of the near-stoichiometric Zn:Fe:LiNbO₃ crystals are investigated.     

(Lu,Y)2SiO5∶Ce3+与SrSO4∶Dy3+材料低温热释光及其测试仪器的研究

为了分析材料在低温下的陷阱能级,获得更多有关缺陷结构的信息,研制了一套由STM32微控制器为核心的低温热释光发光谱测量系统。设计了低温样品室,采用液氮冷却样品;STM32通过控制加热电流,实现样品以恒定速率升温,从而获得低温热释光发光曲线或三维热释光谱。温度测量范围为85~400 K,升温速率范围为0.1~10 K/s。设计了由STM32控制X射线及紫外光源的驱动电路,用于样品的激发。采用高灵敏度CCD实现对三维热释光谱的测量,采用单光子计数器获取二维热释光发光曲线。利用该系统测试了（Lu,Y）₂SiO₅:Ce³⁺（LYSO:Ce³⁺）单晶闪烁体与SrSO₄:Dy³⁺粉末样品的热释光谱及辐射发光光谱。观察到LYSO:Ce³⁺在108,200,380 K左右的热释光峰,发光波长位于390~450 nm之间,是明显的宽带峰。在低温下由于基质的自陷激子（STE）发射所形成的发射峰在166 K时发生猝灭。在309 K时,Ce³⁺发射峰展宽为单一发射峰;SrSO₄:Dy³⁺发光峰温度为178,385 K,发光波长由Dy³⁺离子的能级跃迁决定,在480,575,660,750 nm处呈现窄带发光峰。结果表明,系统人机交互界面友好,实验数据可靠,智能化程度高,操作简单。