不同方法制备Y_3Al_5O_(12)∶Ce~(3+)黄色荧光粉的对比研究（英文）

分别以高温固相法、溶胶-凝胶法和水热-热解法制备了Ce~(3+)掺杂的YAG黄色荧光粉,通过X-射线衍射(XRD)、场发射扫描电镜(FESEM)及荧光光谱(PL)进行表征,考察YAG∶Ce~(3+)黄色荧光粉的晶相、形貌及发光性能对制备方法的依赖性。实验表明,三种方法都实现了Ce~(3+)取代Y~(3+)的位置进入晶格,Ce~(3+)掺杂的YAG荧光粉在晶体结构上都保持立方晶体结构。高温固相法所得样品为不规则球形,粒径尺寸较大;溶胶-凝胶法所得样品为纳米尺度范围,细小颗粒团聚严重,水热-热解法所得样品形貌为球形结构且分散性较好,粒度在10μm左右。荧光光谱显示,三种样品都可被460 nm蓝光有效激发,在550 nm处产生宽带发射,但样品发光强度及量子效率差异较大,该现象主要是由样品形貌及粒径尺寸的差异引起的。     

白光LED用球形Y2.96Al5O12:0.04Ce3+荧光粉的制备及光致发光

采用水热-热解法制备了可用于实现白光LED的Y2.96Al5O12∶0.04Ce3+荧光粉,通过X射线衍射(XRD)、扫描电镜(SEM)、X射线能谱(EDS)及荧光光谱(PL)等对Y2.96Al5O12∶0.04Ce3+荧光粉的物相、形貌及光致发光性能进行了表征。结果表明:水热-热解法制备出了物相纯净、分散性良好的球形Y2.96Al5O12∶0.04Ce3+粉体,该荧光粉可被460nm蓝光有效激发,发射光谱为峰值在550nm的一宽带,且水热-热解法得到的YAG∶Ce3+粉体发射强度优于传统高温固相法合成的YAG:Ce3+荧光粉;通过积分球耦合荧光光谱仪对荧光粉与蓝光芯片配合所得白光LED的量子效率进行了测试,结果表明:水热-热解法制备的Y2.96Al5O12∶0.04Ce3+荧光粉绝对量子效率为88.40%,外量子效率为78.64%,色坐标为(0.453 8,0.531 8),色温为358 4K,该方法制备的Y2.96Al5O12∶0.04Ce3+荧光粉稳定性及数据测定的重现性较好,是一种适用于暖白光LED的高性能黄色荧光粉。     

亚微米级Ca_(2.40)Lu_(0.54)ScMgSi_3O_(12):0.06Ce~(3+)荧光粉的溶胶燃烧法合成与表征

用溶胶燃烧法在1 200℃制备了亚微米级Ca2.40Lu0.54ScMgSi3O12∶0.06Ce3+荧光粉,并对其进行了物相结构、形貌、光致发光性质和热猝灭性质的表征。与传统高温固相法制备的样品相比,溶胶燃烧法不但降低了制备温度,而且制备的Ca2.40Lu0.54ScMgSi3O12∶0.06Ce3+荧光粉的形貌也有所改善。发光性质测试结果表明,亚微米级Ca2.40Lu0.54ScMgSi3O12∶0.06Ce3+荧光粉的发光峰值相比于高温固相法样品有约10 nm的红移,而且样品的热猝灭性质也优于高温固相法样品。     

纳米YAG∶Ce3+, Mn+(Mn+=Ca2+, Gd3+)荧光粉的结构与发光性能

当前商用白光LED器件中YAG∶Ce3+荧光粉的单一黄光发射,导致其缺乏红光限制了器件的应用和发展,在YAG∶Ce3+中掺杂其他离子是解决该问题的有效途径之一。采用溶胶凝胶法制备了系列单掺Ce3+,Ca2+和Gd3+的YAG纳米荧光粉。研究了离子掺杂量对荧光粉的物相、结构、形貌、粒度、发光性能及量子效率的影响,分析了发光机理。结果表明：制备的纳米荧光粉粒径为100～200 nm。Ce3+和Gd3+掺杂时均得到YAG纯相,但晶体结构膨胀,晶面衍射峰向小角度方向移动。样品结晶度随Ce3+和Ca2+(<0.025 mol)掺杂量增大变化不明显,随Gd3+则呈现逐步降低趋势。三种离子掺杂量增大时,Ce3+的晶格能上升,5d能级晶体场劈裂加剧;Gd系列荧光粉激发和发射光谱随掺杂量的增大发生红移,Ce和Ca系列则因掺杂量小表现不明显。荧光粉发光强度随Ce3+掺杂量上升先增大后减小,最佳掺杂量为0.06 mol;随Gd3+掺杂量增加逐步降低;随Ca2+掺杂量增大则急剧下降,0.03 mol掺杂量时荧光强度几乎为零,YAG晶体结构破坏,生成YAM和YAP相。研究的开展,将对后续纳米YAG荧光粉及其相关功能材料的进一步开发使用提供一定的理论依据和实践参考。     

用于白光LED的规则球形YAG:Ce3+荧光粉制备及封装性能研究（英文）

采用高温固相法和筛分法合成了YAG:Ce3+系列黄色荧光粉。采用X射线衍射仪(XRD)、电子扫描显微镜(SEM)、激光粒度分布仪及荧光分光光度计对所制备样品进行了表征。结果表明:所得3种样品形貌规则成球形,粒度分布集中,其中心粒径(D50)分别为29.59,17.40,9.56μm,粒径分布离散度分别为0.85,0.80和0.87。通过Reitveld精修拟合发现,随着荧光粉粒径大小的变化,基质的晶格常数并未发生明显变化。随着中心粒径(D50)逐渐变小,其荧光发射强度逐渐降低,且发生明显的蓝移,同时对蓝光的吸收逐渐减弱。通过对荧光粉与蓝光芯片配合所得白光LED的发光效率、显色指数及色温进行测试发现,当使用相同粉胶比浓度、相同点胶量时,随着荧光粉粒径的减小,所得白光LED的流明效率从109.95 lm/W降低到了99.85 lm/W,而显色指数和色温同时升高。     

Y3Al5O12:Ce3+的余辉和热释光特性

高温固相法合成了Ce3+掺杂的Y3Al5O12(YAG)样品,研究了样品的结构、光致发光和热释发光性质.X射线衍射分析结果表明合成样品为YAG纯相,稀土离子的少量掺杂不改变基质YAG的结构.荧光光谱测试表明在高温空气气氛下Y2.95Al5O12:Ce4+0.05制备过程中存在Ce4+的自还原现象,一部分Ce4+被自还原为Ce3+,导致531nm黄光宽带发射.弱还原气氛下制备的Y2.95Al5O12:Ce3+0.05在紫外光照射后具有黄色长余辉,余辉时间长达35 min.热释光测试表明在Ce3+掺杂的YAG样品中存在热释发光,在弱还原气氛下制备的样品Y2.95Al5O12:Ce3+0.05的热释光随温度变化曲线上有112℃和256℃两个明显的热释光峰;而在空气气氛下制备的样品Y2.95Al5O12:Ce4+0.05的热释光随温度变化曲线上只有128℃一个明显的热释光峰.通过对比研究,热释发光主要来源于YAG基质中缺陷能级所陷俘的Ce3+.     

用于白光LED的Y_(3-x-y)Pr_xGd_yAl_5O_(12):Ce~(3+)荧光粉发光特性研究

以稀土氧化物为原料,采用高温固相法,分别合成了钆、镨、以及钆镨共掺杂的YAG…Ce荧光粉。用荧光分光光度计对这几种荧光粉的激发光谱和发射光谱进行测试。结果表明,这几种荧光粉可以被蓝光(455~470 nm)有效激发;掺杂不同浓度的Gd3+可以使YAG…(Ce,Gd)荧光粉发射光谱的中心波长向红光波段产生不同程度红移;YAG…(Ce,Pr)荧光粉发射光谱新增610 nm处发射峰;YAG…(Ce,Pr,Gd)荧光粉的发射光谱不仅新增610nm处的红峰而且有红移现象,这有效弥补了传统白光LED光谱中红光成份不足这一缺陷,对白光LED在高显色性要求领域的应用有重大的意义。     

白光LED用红色发射荧光粉YVO_4:Ce~(3+)(Gd~(3+))的制备与表征

用高温固相反应法制备了稀土离子Ce3+、Gd3+双掺杂的YVO4发光材料,通过X射线衍射(XRD)、扫描电镜(SEM)、激发以及发射光谱等测试手段对YVO4:Ce3+(Gd3+)荧光粉的制备条件、发光性能以及表面形貌进行了研究。XRD结果表明,在1100℃恒温5 h可得到Ce3+(Gd3+):YVO4纯相。SEM结果显示颗粒基本为球形,粒径约为300~500 nm。激发光谱测试表明,Ce3+(Gd3+):YVO4荧光粉在近紫外光区(232 nm)和蓝光区(424 nm)可以被有效地激发,用424 nm的蓝光激发样品时,Ce3+(Gd3+):YVO4荧光粉在611 nm和659 nm处的发光强度最大;因此,这种荧光粉可以作为组合型白光LED的红色发射荧光粉的候选材料。     

溶胶-凝胶法制备YAG∶Ce,Yb纳米荧光粉及其发光性质研究

使用溶胶-凝胶法在不同煅烧温度下制备了不同掺杂的YAG∶Ce,Yb荧光粉。使用扫描电镜、X射线衍射仪对其形貌、结构进行了表征;采用光致发光、荧光寿命等技术,对其发光性质进行了研究。结果表明:粉体粒径随煅烧温度上升而增大,在1 000℃下,得到平均尺寸~84 nm的纳米荧光粉。溶胶-凝胶法产物与高温固态法产物相比,Yb~(3+)离子发光的猝灭浓度由10%下降至5%。这可能是由于溶胶-凝胶反应产物体系中掺杂离子分布更加均匀所致。     

YAG∶Ce3＋荧光粉的高温固相合成及发光研究

采用高温固相法合成YAG∶Ce3＋发光材料。用正交试验法设计实验,确定Ce3＋掺杂量、焙烧温度、焙烧时间的最佳条件。研究结果发现：（1）荧光粉发光强度的影响因素排列顺序是：焙烧温度＞焙烧时间＞Ce离子掺杂量。其中焙烧温度的影响最为关键,其次是焙烧时间的影响,而Ce离子掺杂量的影响较小。（2）用高温固相法制备YAG∶Ce3＋荧光粉的最佳工艺参数为：焙烧温度1600℃,Ce离子掺杂量0.10 mol ,焙烧时间4 h ,即 A5 B5 C3组合。依此条件,合成的荧光粉发光最好。另一个最优组合是：焙烧温度1600℃,Ce离子掺杂量0.08 mol ,焙烧时间4 h ,即A5 B4 C3组合。依此条件,合成的荧光粉发光也很好,但稍弱于A5B5C3组合。对合成YAG∶Ce3＋发光材料的激发（343和467 nm）、发射（529 nm）光谱的峰形变化及跃迁性质进行了深入分析及指认。     

Eu3+-site occupation in CaTiO3 perovskite material at low temperature

In order to clarify the site occupancy of rare-earth ions in rare-earth doped perovskite materials, the un-doped pure CaTiO₃ and Eu³⁺-doped CaTiO₃ samples with a series of Ca/Ti ratio were synthesized via high-temperature solid-state reaction method. X-ray diffraction (XRD) powder patterns confirm that the crystal structure keeps invariant at various Ca/Ti ratios. Measurement results of unit-cell parameters and X-ray photoelectron spectroscopy (XPS) indicate that Eu³⁺ ions enter into the Ca²⁺ site. The high-resolution photoluminescence spectra of Eu³⁺ ions at 20 K in all samples did not witness a significant change under the excitation at different wavelength, implying that Eu³⁺ ions occupy only one type of site. Considering the small spectral splitting range of ⁵D₀ → ⁷F₂ transition and the large intensity ratio of ⁵D₀ → ⁷F₂/⁵D₀ → ⁷F₁, it can be concluded that Eu³⁺ occupies Ca²⁺ site with larger coordinate numbers rather than Ti⁴⁺ site.     

Er3+、In3+等金属离子对多孔硅光致发光性质的影响

用阳极腐蚀的方法制备了多孔硅样品,用电化学方法在多孔硅中注入Ｅｒ＾３＋、Ｉｎ＾３＋等金属离子,并对注入离子后多孔硅的光致荧光光谱进行了研究,结果表明：注入Ｅｒ＾３＋及Ｉｎ＾３＋后的多孔硅在５８８ｎｍ处的妇光峰强度大大增加,同时发光峰稍有展宽。随着离子注入时间的增长,强度继续增加,但当离子溶液浓度一定时,这种增强对时间具有饱和性。     

Emission analysis of Li6LuY(BO3)3:Tb3+,Dy3+ phosphors

In this paper, we present the synthesis and luminescence properties of Tb³⁺ and Dy³⁺-doped lithium lutetium yttrium borate (Li₆LuY(BO₃)₃) phosphors. We have adopted the well-known solid state reaction method for the synthesis of these phosphors. The emission intensities of the synthesized phosphors were found to reach their maximum, when doped by 1 mol% of Tb³⁺ and 3 mol% of Dy³⁺, beyond which emission intensities decrease due to concentration quenching. The homogeneous phase, crystalline structure and uniform morphology of the synthesized phosphors were confirmed by X-ray diffraction analysis (XRD) and Scanning electron microscopy (SEM). The X-ray and UV–VIS-induced luminescence, decay time and CIE chromaticity were investigated for the synthesized phosphors.The X-ray induced integrated light yield was measured to be 82% for Li₆LuY(BO₃)₃:Tb³⁺ (LLYBO) and 59% for Li₆LuY(BO₃)₃:Dy³⁺ of that of commercially available X-ray imaging material; Gd₂O₂S:Tb³⁺ (Gadox).LLYBO:Tb³⁺ phosphor displayed five major emission bands that correspond to ⁵D_j → ⁷F_j transitions. The 1931 Commission Internationale de l'Eclairage (CIE) chromaticity coordinates were also measured.     

Cr3+ doped Al2O3 nanoparticles: Effect of Cr3+ content in intensifying red emission

Cr³⁺-doped α-Al₂O₃ nanoparticles (Al_2−xCr_xO₃, 0.005 ≤ x ≤ 0.05) were synthesized by co-precipitation method. X-ray diffraction (XRD) patterns of Cr³⁺:Al₂O₃ nanoparticles revealed the crystallite size of ∼53 nm and electron microscopy (SEM & TEM) confirmed the spherical nanoparticle formation. Diffuse reflectance spectra (DRS) displayed peaks at 406 and 558 nm corresponding to the Cr³⁺ transitions which became prominent with the increase in Cr³⁺ concentration which was also evidenced by the gradually increasing pink coloration of the samples. Photoluminescence (PL) studies showed the sharp red emission at 694 nm (ruby line) which was observed for all samples. The Dq/B value for all samples was found to be greater than 2.3 confirming the presence of Cr³⁺ ions in the octahedral sites. Chromaticity diagrams displayed the maximum red appearance for the sample with x = 0.01 and a lifetime of 4 ms. The synthesized Cr³⁺:Al₂O₃ nanoparticles with smaller crystallite sizes and narrow near monochromatic emission can be used in various applications including sensing, lasing, and bioimaging applications.     

Growth and spectroscopic properties of Yb-doped Li6Y(BO3)3 single crystal

The spectroscopic properties of high-quality Czochralski grown 20% Yb³⁺-doped Li₆Y(BO₃)₃ single crystal as new promising laser material are presented. The crystal was seeded-grown in the 〈0 1 0〉 direction and its crystallinity was measured using X-ray rocking curve analysis. Low temperature transmission spectrum exhibits broad bands in a short range of wavelengths and two sharp lines at 972.5 and 978 nm, interpreted as two zero-lines of two nonequivalent Yb³⁺ centers inside the lattice. The fluorescence lifetimes associated to these two intense lines are different: 0.867 and 1.33 ms. An attempt of determination of the Stark sublevels energies of the ⁴F_5/2 and ⁴F_7/2 manifolds of the two Yb³⁺ nonequivalent ions is given. The polarized absorption and emission spectra were also recorded at room temperature and we conclude that the most favorable emission line for laser application could be around 1042 nm in n_g polarization.     

Optical properties of CH3NH3PbI3 crystal grown using inverse temperature crystallization

Perovskite CH₃NH₃PbI₃ (MAPbI₃) single crystal was grown using inverse temperature crystallization method. Crystallinity of the perovskite was confirmed by X-ray diffraction. Photoluminescence (PL) spectra revealed abnormal behavior due to a temperature-induced orthorhombic to the tetragonal phase transition. Four PL emission peaks, A, B, C, and D, were observed in the low temperature regime. Peaks A and B were observed at 756 and 776?nm?at 12?K, and were blue-shifted and disappeared at 130 and 70?K, respectively. Peaks C and D were observed at 789 and 807?nm?at 40?K and were also blue-shifted to 780 and 794?nm?at 100?K. On the other hand, the peak C red-shifted to 799?nm from 100 to 140?K because of an orthorhombic to the tetragonal phase change and was also blue-shifted above 140?K. From the excitation intensity- and temperature-dependent PL results, peaks A and B were assigned to the free-exciton and bound-exciton of the orthorhombic phase crystal, respectively. In addition, peaks C and D were associated with the free-exciton and bound-exciton of the tetragonal phase crystal, respectively. The activation energy of peak C was calculated to be 98?meV from temperature dependence of the PL intensity.     

Broadband infrared luminescence in Yb-doped Bi2O3–GeO2 glasses

The Yb-doped Bi₂O₃–GeO₂ glasses were prepared by the conventional melt quenching technique. Near-infrared (NIR) broadband emission was found at about 1024 nm, and 1330 nm (under 785 nm excitation), and the measured fluorescent lifetime was about several hundred microseconds. The emission intensity of Yb-doped Bi₂O₃–GeO₂ glasses increased with increasing of Yb dopant in our experiments. The NIR emission should be related to Yb³⁺ and lower valence Bi ions.     

NPB/Alq3有机量子阱光电特性研究

利用热蒸发的方法制备了有机量子阱发光器件和Alq3单层发光器件,其中NPB(N,N′-Di-[(lnaphthalenyl)-N,N′-diphenyl]-(1,1′-biphenyl)-4,4′-diamine)作垒层,Alq3(Tris-(8-quinolinolato) aluminum)作阱层,量子阱结构类似于无机半导体的Ⅱ型量子阱结构.实验发现有机量子阱发光器件结构中存在垒层向阱层的F(o)rster无辐射共振能量转移,具有良好的电流-电压特性,光谱的窄化及蓝移,并且光谱的蓝移程度随电压的增大而逐渐增强.     

Photoluminescence and radioluminescence study of NaMgF3:Eu nanoparticles

Photoluminescence (PL) and radioluminescence (RL) measurements were made on small (∼25 nm) NaMgF₃ nanoparticles doped with Eu concentrations ranging from 0.1% to 5%. We find that they contained Eu³⁺, Eu²⁺, and an additional unidentified defect with a broad PL emission ∼470 nm. Similar to previous measurements on larger (57 nm–77 nm) NaMgF₃:Eu nanoparticles with 1% Eu and 5% Eu, we find that the PL lifetime decreases with increasing Eu concentration that can be attributed to Eu energy transfer to non-radiative recombination sites. However, there is no change in the fraction of Eu³⁺ distorted sites. The ∼470 nm PL defect peak was also reported for larger nanoparticles, which suggests that this peak arises from similar unidentified point defects. However, the activated non-radiative decay for the small nanoparticles has a significantly lower activation energy. The Eu³⁺ RL decreases by only 2.3% at 10 kGy for low Eu concentrations.     

Tailoring red-green-blue emission from Er3+, Eu3+ and Tb3+ doped Y2O3 nanocrystals produced via PVA-assisted sol-gel route

Y₂O₃ luminescent nanoparticles were synthesized via PVA-assisted sol-gel method and their structural and optical properties were investigated. Effects of rare earth (Er³⁺, Eu³⁺ and Tb³⁺) doping on luminescence properties of the produced nanophosphors have been investigated under NIR (800 nm) and UV (240–300 nm) excitation. Intense infrared to red and green emissions were observed and a weak blue upconverted luminescence was also detected. Moreover, it was observed that changing the doping ions, the color emitted by the samples could be modified and different combinations of UV excitation and doping produced effective white light emissions. The obtained results demonstrate that PVA-assisted sol-gel is an effective methodology for the synthesis of rare-earth doped Y₂O₃ nanophosphors.