光谱探针法确定Eu3+:ThO2的格位对称性及选择激发下样品的光致发光研究

测量和分析了不同温度下Eu³⁺:ThO₂的激发光谱、发射光谱和荧光 衰减曲线.Eu³⁺:ThO₂晶体是用熔融法生长的.通过12K下格位选择激 发下的发射光谱测量,利用晶场理论,确定了Eu³⁺在ThO₂占据Oh和C_3v两种格位.列表给出了两种格位Eu³⁺离子的晶场能 级和室温及12K下的荧光寿命.讨论了温度对能     

掺杂浓度和烧结温度对CaWO4:Eu3+发光性能的影响

采用微乳液法合成掺杂浓度不同和烧结温度不同的CaWO₄:Eu³⁺系列荧光体, 这些荧光体都具有Eu³⁺离子的特征荧光发射. 在不同温度烧结后, 高浓度掺杂的样品(Eu³⁺掺杂30或50 mol%)可获得最大的发光强度, 低浓度掺杂的样品(掺杂0.5—2 mol%)在800 ℃烧结时也可获得优异的发光强度. 实验结果表明, Eu³⁺离子高浓度掺杂的CaWO₄:Eu³⁺在紫外光激发下可成为高效发光的荧光粉.     

高温高压合成的SrSiO3:Eu3+Bi3+的结构及其对发光特性的影响

 本文首次报道在3.15 GPa、1 200 ℃高温高压条件下合成出了SrSiO₃:Eu³⁺Bi³⁺发光材料，并与常压合成产物相比较，研究了高温高压合成产物的结构以及合成压力、温度对发光特性的影响。结果表明，高压合成产物SrSiO₃:Eu³⁺Bi³⁺的结构为膺正交（单斜）结构，而常压合成的为六角结构，高压使发光强度下降，量子发光效率下降了88%，谱线红移达756 cm^-1，半值宽度也显著增加，发光性能的改变是由于压致结构的变化引起的。     

Eu3+掺杂CaWO4红色荧光粉发光性质的浓度依赖关系研究

采用共沉淀法制备了不同Eu³⁺掺杂浓度的CaWO₄荧光粉材料.通过X射线衍射和场发射扫描电镜技术对样品的结构和形貌进行了表征.测量了各样品的激发光谱、发射光谱和荧光衰减曲线, 计算了各样品的部分Judd-Oflet (J-O)参数和^5D_0 (Eu³⁺)能级量子效率,以及荧光粉的色坐标, 讨论了样品电荷迁移带相对强度、J-O参数、量子效率与掺杂浓度的依赖关系.对Eu³⁺掺杂的CaWO₄ 发光材料的光致发光性质的研究表明,在CaWO₄: Eu³⁺中⁵D₀→⁷F₂跃迁的616~nm 红色发光能被394.5~nm和465~nm的激发光有效激发,具有近紫外(或蓝光)激发效率高和猝灭浓度大的优点, 有潜力成为高效的近紫外(或蓝光)激发白光发光二极管用红色荧光粉材料.     

Eu2+, Cr3+共掺杂的MAl12O19 (M=Ca, Sr, Ba) 的发光性质及能量传递

三基色荧光粉中, 红色荧光粉性能较差, 为获得性能优良的红色荧光粉, 本文采用高温固相法合成了Eu²⁺, Cr³⁺单掺杂及共掺杂的碱土金属多铝酸盐MAl₁₂O₁₉ (M =Ca, Sr, Ba) 发光体. 实验表明, 在以上三种基质中均存在Eu²⁺→Cr³⁺的能量传递, 利用能量传递可以有效将Eu²⁺的蓝光或绿光转换为红光. 三种碱土金属多铝酸盐基质的晶体结构相似,但Eu²⁺, Cr³⁺发光受晶体场影响,导致在不同的基质中Eu²⁺, Cr³⁺间能量传递效率不同.通过光谱分析及能量传递效率计算发现, 相同掺杂浓度下,CaAl₁₂O₁₉中Eu²⁺→Cr³⁺的能量传递效率最高,SrAl₁₂O₁₉次之, BaAl₁₂O₁₉最低.红光转换率在CaAl₁₂O₁₉中最高.     

NaGdF4:Eu3+和GdBaB9O16的VUV荧光性质

在真空紫外光激发下,六万结构的NaGdF₄:Eu³⁺中的Gd³⁺离子吸收一个光子,将能量分两步传递给Eu³⁺离子,发生红色双光子发射.立方结构的NaGdF₄:Eu³⁺中存在一定量的氧离子取代缺陷,使Gd³⁺离子4f-5d跃迁移到177nm附近,这与惰性气体放电产生的VUV光波长一致,并且其荧光色纯度较高.在VUV激发下,GdBaB₉O₁₆中的Gd³⁺离子发生双光子(紫外和红色或远红外)发射.     

BaZr(BO3)2:Eu的合成及发光性能研究

用硝酸盐热分解法成功制备了BaZr(BO₃)₂:Eu(Eu³⁺的掺杂量为摩尔分数5％)荧光材料，并研究了其在254及147nm光束激发下的发光特性.254nm光束激发下的发射主峰位于612nm处，归属于Eu³⁺的⁵D₀—⁷F₂的电偶极跃迁，但在147nm光束激发下的发射主峰位于592nm处，归属于Eu³⁺的相似文献   

Eu2+,Mn2+在BaZnP2O7中的发光及Eu2+→Mn2+能量传递

采用高温固相法合成了BaZnP₂O₇:Eu²⁺,Mn²⁺荧光粉，并对其发光性质及Eu²⁺对Mn²⁺的能量传递机理进行了研究.Eu²⁺和Mn²⁺在380 nm和670nm的发射峰分别由Eu²⁺的5d—4f跃迁和Mn²⁺的⁴T₁(^{4相似文献}   

超声喷雾共沉淀法制备的Lu3Al5O12∶Eu3+ 纳米粉体发光特性

采用新型超声喷雾共沉淀法技术,以Lu₂O₃、Eu₂O₃、Al(NO₃)₃·9H₂O为原料,制备了不同浓度Eu³⁺离子掺杂的Lu₃Al₅O₁₂纳米粉体.用X射线粉末衍射表征了获得纳米粉体的相,用扫描电镜观察了纳米粒子的形貌.测定了粉体的激发光谱、⁷F₀-⁵D₂声子边带谱与发射光谱.研究了不同高温烧结温度与Eu³⁺掺杂浓度对纳米粒子的发光强度与粒子形貌的影响规律.研究表明,当烧结温度高于900 ℃时,粉体发光强度明显增强,并且随着煅烧温度的增加,发光强度有所增强.Eu³⁺离子的最佳掺杂浓度为5~7 mol%.根据稀土离子Eu³⁺光学跃起矩阵元的特点,从发射光谱获得Eu³⁺光学跃起的J-O参量Ω₂与Ω₄.在Eu³⁺掺杂浓度均为5 mol%时,其强度参量达最小,电-声子耦合最强.然后随着掺杂浓度的进一步提高,强度参量略有增加,电-声子耦合减弱.说明Eu-O键强增加,共价性增强,Eu³⁺的局域环境对称性降低.Ω₂值低于Eu³⁺在玻璃与晶体基质中的情况,这是由于纳米粒子中存在着大量的缺陷以及晶体的结构畸变导致纳米粒子的对称性下降所致.     

La2Zr2O7:Eu3+纳米棒的合成、表征及其荧光性能

采用传统固相法和水热法成功地制备出棒状La₂Zr₂O₇:Eu³⁺荧光粉. 利用X射线粉末衍射仪、透射电镜和荧光光谱仪等分析了产物的结构、形貌和发光特性. 结果表明红色荧光粉La₂Zr₂O₇:Eu³⁺有良好的晶相,属于立方结构,空间点群为Fd3m; 其形貌主要为纳米棒, 平均直径约47 nm, 长度为50～700 nm. 并对纳米棒的生长机理进行了探讨. 在466 nm蓝光激发下,La₂Zr₂O₇:Eu³⁺荧光粉能发射出Eu³⁺的特征红色荧光,发射主峰位于616 nm处,归属于Eu³⁺的⁵DO_→⁷F2_{超灵敏电偶极跃迁.此外,在产物的发射光谱中能够观察到⁵D}1_→⁷FJ _{(J=0, 1, 2)跃迁和⁵D}1_→⁷FJ _{(J=1, 2, 4)跃迁的劈裂峰,这说明Eu³⁺处在低对称性的晶体场格位中.}     

基质发光晶体Na5Eu(MoO4)4在高压下的光谱与晶体场参数

对白钨矿型化学计量的基质发光晶体四钼酸铕钠Na₅Eu(MoO₄)₄在室温下的高压光谱用金刚石对顶砧高压显微光谱系统进行了研究。确定了Eu³⁺各发射谱线的压力红移率。按晶场理论简化方法推导了能级的晶场参数表达式,并按实验数据拟会出晶场参数随压力的移动率。还将上述结果与掺杂发光材料YVO₄:Eu的高压光谱结果作了对比。 关键词：     

Photoluminescence of Eu in SrGa2S4

A photoluminescence (PL) study of the green-emitting SrGa₂S₄:Eu²⁺ phosphor is reported. Diffuse reflectance, excitation, and emission spectra were examined with the aim to enlarge the fundamental knowledge about the emission of the Eu²⁺ ion in this lattice. The thermal dependence of the radiative properties was investigated. In particular, the Stokes shift, the crystal field splitting and the activation energy of the thermal quenching were determined. By combining these results with the information presented in literature, we discussed the location of the Eu²⁺ levels relative to the valence and conduction bands of SrGa₂S₄.     

Radiative properties of Eu in BaGa2S4

A photoluminescence study of the blue-green emitting BaGa₂S₄:Eu²⁺ phosphor is reported. Diffuse reflectance, excitation and emission spectra were examined with the aim to enlarge the fundamental knowledge about the emission of the Eu²⁺ rare earth ion in this lattice. The thermal dependence of the radiative properties and the influence of the Eu²⁺ concentration were investigated. The Stokes shift, the crystal field splitting and the activation energy of the thermal quenching were determined. By combining these results with data available in literature, we discussed the radiative properties of the BaAl₂S₄:Eu²⁺ blue phosphor in relation with those determined in this study for the isostructural BaGa₂S₄:Eu²⁺ phosphor.     

Luminescent characterization of CaAl2S4:Eu powder

The photoluminescent (PL) emission and excitation behaviour of green-emitting CaAl₂S₄:Eu²⁺ powder phosphor is reported in detail. CaAl₂S₄:Eu²⁺ emission provides good CIE colour coordinates (x=0.141; y=0.721) for the green component in display applications. Powder with a dopant concentration of 8.5 mol% shows the highest luminescence efficiency. Temperature dependence of the radiative properties, such as luminescence intensity and decay time, was investigated. In particular, the Stokes shift, the mean phonon energy, the redshift, the energy of the f→d and d→f transition and the crystal field splitting of the CaAl₂S₄:Eu²⁺ emission were determined. The thermal quenching of the emission was examined.     

Preparation and characterization of nanosized (Y,Bi)VO4:Eu and Y(V,P)O4:Eu red phosphors

Nanosized luminescent (Y,Bi)VO₄:Eu³⁺ and Y(V,P)O₄:Eu³⁺ were synthesized at low temperatures either by a coprecipitation method or by a hydrothermal method from aqueous solutions. The effect of Bi³⁺ ion or P⁵⁺ ion content in the lattice, annealing temperature effects on the crystal structure and the particle size, and the luminescence property of (Y,Bi)VO₄:Eu³⁺ and Y(V,P)O₄:Eu³⁺ nanoparticles were examined with a field-enhanced scanning electron microscopy, XRD, and a spectrofluorometer. The pristine YVO₄:Eu³⁺, (Y,Bi)VO₄:Eu³⁺, or Y(V,P)O₄:Eu³⁺ nanoparticles are 35-50 nm in size. The luminescence spectrum of the Eu³⁺ ion was used to probe its position in the crystal lattice. The dopant ions enter the same lattice sites in the nanocrystalline as in the corresponding bulk material, resulting similar spectral features between them. Photoluminescence intensity is weak for the pristine nanoparticles. Annealing the nanoparticles at temperatures up to 1000 °C results in the increased luminescence intensity (>80% of micrometer-sized phosphors) with the minimal particle growth and the improved particle crystallinity.     

Effect of Sr substitution on photoluminescent properties of BaAl2O4:Eu, Dy

Phosphor material BaAl₂O₄:Eu²⁺, Dy³⁺ with varying compositions of Sr substitution were prepared by the solid-state synthesis method. The phosphor compositions were characterized for their phase and crystallinity by XRD, SEM and TEM. Photoluminescence (PL) properties were investigated measuring PL and decay time for varying Ba/Sr compositions. The PL results show the blue shift in the luminescence properties in Sr substituted BaAl₂O₄:Eu²⁺, Dy³⁺ compared to parent BaAl₂O₄:Eu²⁺, Dy³⁺. It is probably due to the influence of 5d electron states of Eu²⁺ in the crystal field because of atomic size variation causing crystal defects. Dy³⁺ ion doping in the phosphor generates deep traps, which results in long afterglow phosphorescence.     

Fluorescence properties of divalent and trivalent europium ions in CdWO4 single crystals grown by Bridgman method

Optical absorption, excitation, and fluorescence were investigated in Eu ion-doped CdWO₄ single crystal grown by a modified Bridgman method. The results indicate that Eu²⁺ and Eu³⁺ ions coexist in CdWO₄ crystal and an energy transfer occurs between these Eu²⁺ and Eu³⁺ ions. When the crystal is excited by 266-nm light, the energy corresponding to the 4f⁶5d to ⁸S_7/2 transition of Eu²⁺ ions results in the excitation of the Eu³⁺ ions to the ⁵D_J level. The effect on fluorescence of annealing in oxygen at various temperatures was investigated. The excitation intensity of Eu²⁺ ions at 266 nm decreases as annealing temperature increases from 300 K to 1073 K, but it remains at a certain equilibrium level when the annealing temperature is further increased.     

Luminescent properties of Eu and Ce ions in strontium litho-silicate Li2SrSiO4

The luminescent properties of Eu²⁺ and Ce³⁺ ions in Li₂SrSiO₄ have been studied upon excitation in the 2-20 eV region. Based on the results of luminescent measurements, values of the crystal field splitting and the centroid shift of the Ce³⁺5d configuration in Li₂SrSiO₄ were found and compared with those of Ce³⁺ ions in some other inorganic compounds. The Eu²⁺ ions in Li₂SrSiO₄ exhibit a broad band emission with a maximum at 576 nm, which is due to the 4f⁶5d→4f⁷ transition. It was shown that the long-wavelength position of the Eu²⁺ emission in Li₂SrSiO₄ is caused by the large crystal-field splitting of the Eu²⁺ 4f⁶5d configuration and relatively high degree of covalency of the Eu-O bond. The stabilization of Eu²⁺ ions in Li₂SrSiO₄ during the synthesis process requires a strong reducing agent. Two phenomenological approaches to explain the low stability of Eu²⁺ in Li₂SrSiO₄ are also discussed.     

Luminescence and energy transfer in Y2O3 CO-doped with Bi3+ and Eu3+

The emission spectra and decay times of the Y₂O₃ CO-doped with Bi³⁺ and Eu³⁺ have been investigated using site-selective excitation and time-resolved spectroscopy in the temperature range 8–296 K. Evidence for an energy transfer from Eu³⁺(S₆) to Eu³⁺(C₂) is given. The critical transfer distance R₀ = 8.6 Å was found from the decay curve.