Na4Ca3(AlO2)10∶Eu2+,Mn2+荧光粉的发光特性

采用高温固相法,制得一种新型荧光粉Na₄Ca₃(AlO₂)₁₀∶Eu²⁺,Mn²⁺。样品的结构和发光性质分别由X射线衍射谱和荧光光谱来表征。在Na₄Ca₃(AlO₂)₁₀∶Eu²⁺的激发光谱中出现了Eu²⁺的f-d跃迁吸收带;在发射光谱中,出现蓝光发射,峰值位于441 nm。当在Na₄Ca₃(AlO₂)₁₀∶Eu²⁺中掺杂Mn²⁺时,发生了Eu²⁺→Mn²⁺的能量传递,在542 nm处出现了Mn²⁺的发射峰。在Na₄Ca₃(AlO₂)₁₀∶Eu²⁺,Mn²⁺中,随着Mn²⁺浓度的增加,Eu²⁺粒子的发射强度减弱,而Mn²⁺粒子的发射强度增强,且Eu²⁺离子发射的衰减时间缩短,同时色度由蓝光移向白光。     

Eu2+掺杂P2O5-BaO-Na2O-K2O与Na2O-TeO2-ZnO系统玻璃的制备与光谱性质

用高温熔融法,把Eu₂O₃掺入到P₂O₅-BaO-Na₂O-K₂O与Na₂O-TeO₂-ZnO系统玻璃中。测定了玻璃的荧光光谱与激发光谱。结果表明,Eu离子在P₂O₅-BaO-Na₂O-K₂O玻璃中呈现出Eu³⁺态。然而在Na₂O-TeO₂-ZnO系统玻璃中,尽管在空气气氛下,大部分的Eu离子在玻璃中以二价的状态存在。从玻璃的结构及化学组分解释了产生Eu²⁺的原因。在磷酸盐玻璃配料中加入适量的硅粉(Si)作还原剂,能有效地把玻璃中的极大部分Eu³⁺还原成Eu²⁺,获得含Eu²⁺的优质透明磷酸盐玻璃。     

Ba5(PO4)3Cl：Eu2+荧光粉的制备和发光性能研究

以Eu₂O₃、NH₄H₂PO₄、BaCl₂·2H₂O、BaCO₃为原料,用高温固相法制备出Ba₅（PO₄）₃Cl：Eu²⁺荧光粉。用XRD衍射仪和荧光分光光度计分别测试样品的物相结构和荧光性能。结果表明：制备得到的Ba₅（PO₄）₃Cl：Eu²⁺为单相,在245~425 nm范围均有较大吸收,具有最强峰在435 nm的窄带发射。该荧光粉的发光强度受Eu²⁺浓度的影响较大,其发光随着Eu²⁺浓度的增加先增强后减弱。当Eu²⁺摩尔分数为3%时,发光强度达到最大。     

共溅射和离子注入制备的SiO2(Eu)薄膜中Eu3+到Eu2+的转变

采用共溅射方法和Eu离子注入热生长的SiO₂方法得到SiO₂(Eu)薄膜,Eu离子的浓度为4%和0.5%.对样品X射线吸收近边结构(XANES)的研究和分析表明,在高温氮气中发生了Eu³⁺向Eu²⁺的转变.SiO₂(Eu)薄膜高温氮气退火下蓝光的发射证明了这一结论 关键词： 2(Eu)薄膜')" href="#">SiO₂(Eu)薄膜 XANES     

长余辉发光材料CaAl2O4∶Eu2+,Gd3+ 的制备和发光性能研究

采用高温固相法制备了CaAl₂O₄∶Eu²⁺,Gd³⁺ 长余辉发光材料。利用X射线衍射(XRD)和荧光光谱测试等手段对所制备的样品进行结构表征和发光性能的分析,探究Eu²⁺摩尔分数为3.5%,硼酸质量分数为0.5%,Gd³⁺摩尔分数分别为2%,3%,4%,5%时样品的发光性能。研究结果表明:实验成功地合成了CaAl₂O₄∶Eu²⁺,Gd³⁺粉晶,并且Eu²⁺和Gd³⁺的引入并未引起CaAl₂O₄晶体结构的改变。样品的激发光谱和发射光谱均为宽带谱,且发射光谱的最大峰值位于444 nm左右,属于Eu²⁺的4f⁶5d→4f⁷跃迁,所发光为蓝光。蓝色荧光粉CaAl₂O₄∶3.5%Eu²⁺,3%Gd³⁺的发光强度最好。     

一种LED用红色荧光粉BaZn2(BO3)2：Eu3+的合成与发光性能研究

通过高温固相法制得双峰可调节本征半导体发光BaZn₂（BO₃）₂：Eu³⁺荧光粉,此类荧光粉在300~400 nm的紫外波段有很强的吸收。在375 nm的紫外光激发下,该荧光粉产生了两个宽带的发射峰,分别位于550 nm和615 nm处。并且,在395 nm的紫光激发下,荧光粉会由于Eu³⁺离子的⁵D₀→⁷F₂电偶极跃迁产生一个位于615 nm的强宽发射峰,这表明Eu³⁺离子占据了反演对称中心的位置,取代了BaZn₂（BO₃）₂中部分的Ba²⁺离子。当Eu³⁺的摩尔分数达到10%时,发生浓度猝灭。在不同浓度的Eu³⁺离子的掺杂下,BaZn₂（BO₃）₂：Eu³⁺荧光粉的发光从黄色延伸到红色,实现了荧光粉的色度可调。     

Sr2MgSi2O7∶Eu2+,Eu3+发光性能及颜色调控

采用静电纺丝法在不同气氛下制备了Sr₂MgSi₂O₇∶Eu²⁺,Eu³⁺纤维,研究其晶体结构和形貌;将纤维与聚二甲基硅氧烷(PDMS)复合后获得Sr₂MgSi₂O₇∶Eu²⁺,Eu³⁺-PDMS复合材料,研究其光致发光和应力发光性能。研究结果显示,氮气、空气下制备样品的XPS图谱同时出现Eu²⁺和Eu³⁺结合能特征峰;在360 nm和395 nm激发下复合材料的光致发光光谱中,不但有Eu²⁺位于469 nm处的蓝色宽带发射,还包含Eu³⁺位于615 nm的多个红色窄带发射。因为Eu³⁺在电荷补偿下还原成Eu²⁺并在刚性结构保护下不被氧化,证实了Eu³⁺在Sr₂MgSi₂O     

非晶纳米发光材料(Y,Eu)2O3-SiO2发射光谱的分析研究

EXAFS测定表明sol-gel方法制备的纳米非晶(Y,Eu)₂O₃-SiO₂发光材料中,发光中心Eu³⁺的局域环境和晶态X₂型Y₂SiO₅Eu中Eu³⁺离子的局域环境相似。以此结构为依据,用M. F. Reid的方案计算了晶场迭加模型中的能级参数及光谱强度参数,并得到了与实验结果基本一致的理论光谱图.     

Eu2+掺杂浓度对Ca2MgSi2O7∶Eu2+荧光粉发光特性的影响

采用化学共沉淀法制备了Ca_2-xMgSi₂O₇:xEu²⁺绿色荧光粉.用X射线衍射仪、荧光分光光度计及光色综合测试系统对Ca_2-xMgSi₂O₇:xEu²⁺绿色荧光粉的相结构、发光性能进行了测试.结果表明:其激发光谱分布在300–480 nm波长范围,谱峰位于389,430 nm处,可以被InGaN管芯产生的360–480 nm辐射有效激发;在波长为430 nm蓝光激发下,其发射光谱谱峰位于531 nm处.Ca_2-xMgSi₂O₇:xEu²⁺绿色荧光粉的发光强度随Eu²⁺掺杂量的增加而增强,当Eu²⁺掺杂量x为0.04时,发光强度达到最大值,而后开始降低,发生浓度猝灭.根据Dexter能量共振理论,浓度猝灭是由电偶极-电偶极相互作用引起的. 关键词： 2MgSi₂O₇∶Eu²⁺')" href="#">Ca₂MgSi₂O₇∶Eu²⁺ 绿色荧光粉 发光特性 白光发光二极管     

Bi3+掺杂对Sr2MgSi2O7∶Eu2+荧光粉的结构及发光性能的影响

采用溶胶-凝胶法在还原气氛下制备了Sr₂MgSi₂O₇∶Eu²⁺,xBi³⁺(x=0,0.02,0.04,0.06,0.08,0.1)荧光粉,并用XRD、TG-DTA及激发与发射谱仪对样品的结构及发光性能进行了表征。结果发现:单掺杂Bi³⁺的Sr₂MgSi₂O₇样品的发射光谱所用的材料的激发光谱为一主峰为286 nm的宽带谱,这是由于激发态时Bi³⁺的³P₁→¹S₀电子能级跃迁而造成的;单掺杂Eu²⁺的Sr₂MgSi₂O₇样品的发射光谱所用的材料的激发光谱为一主峰为358 nm的宽带谱,这是典型的Eu²⁺的4f⁶5d¹→4f⁷跃迁而引起的。当Bi³⁺离子掺杂到Sr₂MgSi₂O₇∶Eu²⁺样品的摩尔分数为0.04时,样品的发射强度是未掺杂Bi³⁺离子样品的1.9倍。     

ESR spectra of Eu centers in defect Ga2S3 single crystals

In this paper, the author presents the results of measurements of the low-temperature and angular dependences of the ESR spectra of Eu²⁺ centers in defect Ga₂S₃ single crystals in the temperature range 8–29 K and for 0–180° orientations of the static magnetic field. The electron structure of impurity ¹⁵¹Eu atoms in Ga₂S₃:Eu single crystals has been studied by using the ESR method at different doping proportions of Eu atoms. Ga₂S₃ single crystals were grown from the melt using the Bridgman method. The Eu concentration was determined by atomic absorption analysis and X–ray fluorescence analysis (XRFA). By investigation on the ESR spectra, the author has first determined the values of charge states for Eu, which have turned out to be a Eu²⁺(4f⁷) ion with spin S=7/2, g=4.18±0.02 and concentration of the states of Eu N=6.3×10¹⁴ cm⁻³.     

Exchange and hyperfine fields acting on dilute Eu In SmCo5, Sm2(Co1-xFex)17 and Sm2CoxMy( rm M = Fe, Cu, Zn, Zr)

Mössbauer source experiments of dilute ¹⁵³Eu and ⁵⁷Fe in SmCo₅ and ¹⁵³Eu in Sm₂(Co_1-xFe_x)₁₇ and Sm₂ Co_x M_y at 4.1 K were performed. After the ${}^{153}\text{Sm}\text{→β?}{}^{153}$ decay the Eu ion is trivalent and exhibits extremely large hyperfine interactions due to strong exchange fields. Since the exchange interactions are comparable to the Eu³⁺ spin-orbit coupling, we calculated the expectation values of the Eu³⁺ spin, magnetic hyperfine field and electric field gradient as a function of exchange field and second order crystalline field, by diagonalization of the full Hamiltonian of spin orbit, exchange and crystalline field. For SmCo₅ and Sm₂(Co_1-xFe_x)₁₇ the exchange and crystalline fields are known and thus allow us to analyze our experimental results and obtain the polarized conduction electron contributions to the magnetic hyperfine field. The contribution due to magnetic neighbour polarization of conduction electrons is found to be linear in exchange field. The experimental results together with the theoretical analysis yield the Eu electric field gradient 4f Sternheimer shielding factor R_Q to be 0.26±04. It is shown that Mössbauer studies of two probes (¹⁵⁵Gd and Eu³⁺) in magnetic systems yield directly the second order crystalline field, the exchange field and the various contributions to the hyperfine field acting on the Eu nucleus. From the experimentally measured magnetic hyperfine fields alone, approximate values for the exchange fields in the mixed systems Sm₂Co_xM_y were determined.     

Influence of Eu doping content on photoluminescence of Gd2O3:Eu phosphors prepared by liquid-phase reaction method

Europium-doped cubic Gd₂O₃:Eu³⁺ nanoparticles containing various activator content in the range of 5-15 wt% were synthesized by a liquid-phase reaction method to investigate the influence of Eu³⁺ loading on the optical properties of phosphors by using XRD, TEM, BET, spectrometer and fluorometer. The size of Gd₂O₃:Eu³⁺ powders was in the range 21-41 nm. The phosphors showed an initial increase in luminescence and then a subsequent decrease with further doping (above 10 wt%). The decay time was reduced with increasing Eu loading; however, it decreased significantly above the 10% Eu doping. From spectroscopic studies, the Eu³⁺ doping ion distribution was uniform and homogeneous up to the 10 wt% loading because no concentration quenching effect was observed. However, further Eu³⁺ doping above 10 wt% reduced the luminescence due to the concentration quenching effect, as deduced from the shortening of the decay time.     

Self-compensation characteristics of Eu ions in BaTiO3

In order to clarify whether the mixed valence of Eu²⁺/Eu³⁺ exists in a self-compensation mode in Eu-doped BaTiO₃, the site occupation and valence state of Eu ions in barium titanate were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), electron spin resonance (ESR), Raman spectroscopy (RS), and dielectric measurements. The results indicate that Eu ions may enter both Ba- and Ti-sites as Eu³⁺, forming a self-compensation mode with the amphoteric behavior. Self-compensation characteristics of Eu ions in BaTiO₃ are reflected by an expansion in unit cell volume, evolution of the 830 cm^− 1 Raman band, strong diffusion of the dielectric peak, disappearance of the Eu²⁺ ESR broad signal, and a g = 2.004 signal independent of temperature.     

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.     

Photoluminescence of Eu single doped and Eu/Dy codoped Sr2Al2SiO7 phosphors with long persistence

This paper reports the preparation of long persistent Sr₂Al₂SiO₇:Eu²⁺ and Sr₂Al₂SiO₇:Eu²⁺, Dy³⁺ phosphors and the comparison of their photoluminescent properties. The silicate phosphors prepared by solid-state reaction routine showed a broad blue emission peaking at 484 nm when activated by UV illumination. Such a bluish-green emission can be attributed to the intrinsic 4f-5d transitions of Eu²⁺. After the UV source was switched off, long persistent phosphorescence could be observed by naked eyes for both samples in darkness. Afterglow measurements revealed that Eu/Dy codoped phosphor possesses better afterglow properties than the Eu single doped one, since the maximum lifetime (τ_max=99 s) of the photons calculated from the decay profile is much larger than that of the Eu single doped phosphor (τ_max=82 s). TSL results suggested that the difference in afterglow properties was caused by the difference in the electron traps within the crystal lattice. For Eu/Dy codoped phosphor, the doping of Dy ions produced electron traps with trap depth of 0.52 eV, which is suitable and therefore leads to good persistence. However, in the case of Eu single doped phosphor, the trap depth is 0.88 eV, which is really too deep an energy barrier to overcome, and therefore a poor persistence was observed in the experiment.     

Origin of PL intensity increase of CaMgSi2O6:Eu phosphor after baking process for PDPs application

We have synthesized blue-emitting CaMgSi₂O₆:Eu²⁺ (CMS) and evaluated its thermal stability after baking process. To evaluate its thermal stability, CMS was baked in air at 500 and 600 °C for 20 min, respectively, and compared with BaMgAl₁₀O₁₇:Eu²⁺ (BAM) treated in the same condition. After baking process, CMS showed somewhat increased photoluminescence (PL) intensity with baking temperature. To investigate the reasons behind the increase of PL intensity after baking process, vacuum ultraviolet (VUV)/PL, electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS) techniques were applied. From the ESR and the XPS analyses, it is noted that spectral intensity of Eu²⁺ ion somewhat increased. It was believed that due to charge balance Eu³⁺ ions reduced to Eu²⁺ ions during the baking process in air. It is clear that the concentration of Eu²⁺ increased after the baking process in air and it leads to slight increase of the VUV/PL intensity of CMS phosphor.     

Photoluminescence properties of Sr1-xSi2O2N2: Eux as green to yellow-emitting phosphor for blue pumped white LEDs

This study evaluated potential applications of green to yellow-emitting phosphors (Sr_1−xSi₂O₂N₂: Eu²⁺_x) in blue pumped white light emitting diodes. Sr_1-xSi₂O₂N₂: Eu²⁺_x was synthesized at different Eu²⁺ doping concentrations at 1450 °C for 5 h under a reducing nitrogen atmosphere containing 5% H₂ using a conventional solid reaction method. The X-ray diffraction patterns of the prepared phosphor (Sr_1-xSi₂O₂N₂: Eu²⁺_x) were indexed to the SrSi₂O₂N₂ phase and an unknown intermediate phase. The photoluminescence properties of these phosphors (Sr_1−xSi₂O₂N₂: Eu²⁺_x) showed that the samples were excited from the UV to visible region due to the strong crystal field splitting of the Eu²⁺ ion. The emission spectra under excitation of 450 nm showed a bright color at 545-561 nm. The emission intensity increased gradually with increasing Eu²⁺ doping concentration ratio from 0.05 to 0.15. However, the emission intensity decreased suddenly when the Eu²⁺ concentration ratio was >0.2. As the doping concentration of Eu²⁺ was increased, there was a red shift in the continuous emission peak. These results suggest that Sr_1-xSi₂O₂N₂: Eu₂⁺_x phosphor can be used in blue-pumped white light emitting diodes.     

Photoluminescence in MgxSr1−xAl2O4:Eu, Ndand electron-vibrational interaction in the Eu 5d states

Green phosphor compositions Mg_xSr_1−xAl₂O₄:Eu, Nd (with x=0.05-0.25) were prepared by solid state reaction method. The effect of Mg substitution on photoluminescence characteristics was investigated. The photoluminescence show intense green emission for MgSrAl₂O₄:Eu²⁺, Nd³⁺ with long persistence. This green emission corresponds to transitions from 4f⁶5d¹ to 4f⁷ of Eu²⁺ ion. Comparative analysis of the excitation and emission spectra were used to evaluate the crystal field splitting of the 5d states of Eu²⁺ and the parameters of electron-vibrational interaction, such as Huang-Rhys factor, effective phonon energy, and zero-phonon line position.