纳米级MgSiO3∶Mn2+,Nd3+红色发光材料的制备及发光性能

采用静电纺丝法制备MgO,SiO2,Nd2O3,MnCO3与PVA膜混合物,再通过高温固相法制备长余辉发光材料MgSiO3∶Mn2+,Nd3+,对这种红色长余辉材料的发光性能进行了研究。借助SEM对其表面形态进行表征,激发光谱、发射光谱和余辉衰减曲线表征样品的发光性能。研究发现,PVA及纺丝工艺没有对MgSiO3∶Mn2+,Nd3+样品的晶体结构造成破坏,样品发射峰型没有变化,相对可见光样品对紫外光的吸收更好。采用静电纺丝法制备的发光材料与高温固相法制备的发光材料相比其发光性能及粒径都有一定程度的改善。     

Zn2+、Cr3+掺杂对水热合成纳米CoAl2O4尖晶石色料的影响

以CoCl2·6H2O、ZnCl2、AlCl3和CrCl3·6H2O为原料,采用水热法合成了CoAl2O4(AB2O4)尖晶石型纳米钴蓝色料.采用色度分析、X射线衍射(XRD)、透射电镜(TEM)以及高分辨透射电镜(HRTEM)等研究了A位掺杂Zn2+和B位掺杂Cr3+时不同掺杂量以及不同水热合成温度对样品呈色、晶相组成及CoAl2O4尖晶石的晶粒大小、发育程度和晶面间距的影响.结果表明,掺杂Zn2+、Cr3+所得固溶体型钴蓝色料晶粒发育均不完整,颗粒较于相同水热条件下获得的未掺杂样品更细小.A位掺杂Zn2+可降低CoAl2O4色料的合成温度,在230℃便能制得呈色较佳的Co0.95Zn0.05Al2O4钴蓝色料.随着Zn2+掺杂量的增加,合成产物由蓝色转为绿色,且呈色逐渐变浅.B位Cr3+掺杂则随着掺杂量的增加,产物从蓝色逐步转为绿色,但呈色逐渐变深.就两者相比较,A位掺杂Zn2+更有利于色料明度值的提高而呈色鲜亮.     

MgGa2O4∶Cr3+,Al3+近红外发光长余辉纳米粒子的制备及发光性能研究

利用乙二醇辅助共沉淀法,制备了小尺寸近红外发光Al³⁺共掺杂镓酸镁(MgGa₂O₄)∶0.3%Cr³⁺(MGO∶0.3%Cr³⁺,Al³⁺)长余辉发光纳米粒子(PLNP),考察了Al³⁺掺杂对MGO∶0.3%Cr³⁺晶体结构和光学性质的影响。研究结果表明,Al³⁺掺杂对MGO∶0.3%Cr³⁺的晶体结构无影响,但能提高MGO∶0.3%Cr³⁺的发光强度。当Al³⁺掺杂量为0.4%(摩尔分数)时,MGO∶0.3%Cr³⁺,0.4%Al³⁺(Al³⁺、Cr³⁺相对于Ga³⁺的物质的量比,摩尔分数)PLNP发光强度最强,余辉平均发光寿命从46.98s(MGO∶0.3%Cr³⁺)增大至78.75s(MGO...     

Nd3+:Gd3Ga5O12晶体的热物理性能研究

提拉法生长了Nd^3＋：Gd3Ga5O12（Nd：GGG）单晶，用差示扫描量热法（DSC）和激光脉冲法分别测量了Nd：GGG激光晶体的比热和热扩散系数，计算得到晶体的导热系数，与用PPMS测量得到的导热系数相吻合．实验结果表明：Nd：GGG激光晶体具有较大的比热和导热系数，具有良好的热物理性能；Nd：GGG晶体的热扩散系数和导热系数随着温度的升高而减小；计算得到晶体的德拜温度为711K．     

Tb3+掺杂对Sr2CeO4∶Eu3+发光性能的影响

以尿素为燃料硼酸为助熔剂,采用燃烧法合成了Sr2CeO4∶Eu3+、Tb3+发光材料。测试结果表明,当Tb3+的掺杂为1%(摩尔分数)时,合成的样品为单相Sr2CeO4斜方晶系结构,其样品的激发光谱为240～370nm的宽带双峰,发射光谱为400～550nm宽带峰,余辉衰减曲线的结果显示,适量的掺杂Tb3+可以提高产品的发光性能。与Sr2CeO4∶Eu3+相比,掺杂Tb3+有利于形成结晶度好的固溶体,样品的发光强度明显提高。     

退火对Cr3+离子掺杂Al2O3薄膜的结构及发光性能影响

用脉冲激光沉积技术在Si(100)基底上制备了纯Al2O3、掺杂浓度为0.3%、1%(质量分数)的Cr3+∶Al2O3薄膜。制备态的薄膜为立方γ-Al2O3结构,经800℃真空条件下退火1h样品的结晶度有所提高,呈现α-Al2O3相与γ-Al2O3相的衍射峰。薄膜基本保持了靶材中原有各元素成分比例,平均粒径为250nm,形貌为条形。与Al2O3粉体相比,制备态薄膜在386nm处的发光峰强度明显提高。这可归因于薄膜中氧空位的增加使双氧空位吸收电子所产生的F2+色心浓度提高。薄膜经真空退火后在332、398nm附近的发光峰强度明显增强,这是由于薄膜中氧空位的增加提高了F+、F色心浓度。与此同时,制备态薄膜在386nm附近发光峰经退火后由386nm蓝移至381nm,可归因于退火后制备态薄膜的内应力得到了释放。1%(质量分数)Cr3+掺杂薄膜在646、694nm出现Cr3+离子由4 T2能级跃迁至4 A2能级及由E-能级跃迁至4 A2能级产生的荧光发光峰。     

溶胶-凝胶法制备Gd4Ga2O9: Dy3+白光发射荧光粉及其性能

通过溶胶-凝胶法制备了具有白光发射的Gd₄Ga₂O₉:x%Dy³⁺荧光粉,利用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、紫外-可见漫反射光谱(UV-Vis DRS)和荧光光谱等对产物的物相结构、形貌、组分和光学性能进行研究,并分析了Dy³⁺掺杂量对样品的影响。XRD结果表明,所制备的样品为Dy³⁺掺杂的Gd₄Ga₂O₉单斜晶体和少量Ga₂O₃杂质相的混合物。紫外-可见漫反射光谱结果表明制备的Dy³⁺掺杂Gd₄Ga₂O₉晶体是一种光学带隙为5.29 eV的直接带隙半导体。荧光检测结果表明Dy³⁺掺杂Gd₄Ga₂O₉荧光粉可被属于Gd³⁺     

近紫外白光LED用红色荧光粉In2（MoO4）3:Eu3+,Bi3+的合成及发光性能

通过固相反应法在1000℃空气气氛中合成了In2(MoO4)3:Eu3+、Bi 3+红色荧光粉。粉体分别用X射线衍射(XRD)、荧光分度计测试。结果表明制备的荧光粉具有单相立方晶体结构,该荧光粉能够被近紫外光(395nm)有效激发,发射高强度的612nm红光。Eu3+浓度为40%(摩尔分数)时,In2(MoO4)3:Eu3+发光强度较高。In2(MoO4)3:0.4Eu3+、Bi 3+荧光粉,Bi 3+浓度为3%(摩尔分数)时,发光强度最大,高于没有掺Bi 3+的In2(MoO4)3:0.4Eu3+荧光粉。和CaMoO4:Eu3+相比,In2(MoO4)3:0.4Eu3+、0.03Bi 3+有较高的发光强度。因此,In2(MoO4)3:0.4Eu3+、0.03Bi 3+是一种可能应用于近紫外白光LED的新型红色荧光粉。     

纳米Gd2O3:Tb3+荧光粉的微乳液法合成及其光致发光性质

利用TX-100/正己醇/正辛烷/水微乳液法合成纳米Gd2O3Tb3+荧光粉,结构表征证实其为单相的氧化钆,掺杂对晶型无影响,粒子大小较均匀,分散性好,较少团聚.TG-DTA测量了Gd2O3Tb3+的晶型最终形成温度为590℃,发射光谱显示出Tb3+的4个特征发射.随着纳米粒子粒径的减少,发光强度逐渐减弱.     

Lu2(MoO4)3:Eu3+荧光粉的制备及热增强发光

采用固相法制备了Lu₂(MoO₄)₃:Eu³⁺系列红色荧光粉,利用X射线粉末衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、能谱仪(EDS)和荧光光谱(PL)仪对制备荧光粉的结构、形貌、元素组成及光致发光性能进行表征与分析。实验结果表明Eu³⁺成功掺入基质晶格中并得到Lu₂(MoO₄)₃:Eu³⁺纯相样品,荧光粉颗粒大小在2μm左右。制备温度依赖样品光致发光结果表明1 000℃下制备Lu₂(MoO₄)₃:Eu³⁺样品发光性能最好。煅烧时间依赖样品光致发光结果表明1 000℃下煅烧时间为6 h时样品发光效果最好。反常于荧光粉发光热猝灭现象,Lu₂(MoO₄)₃:Eu³⁺样品在外界测试温度为250℃左右时出现热增强...     

Cr-Tm ion pairs in Gd3Ga5O12 garnet

A study is presented about Cr³⁺→Tm³⁺ energy transfers in Gd₃Ga₅O₁₂ garnet at 10 K. By time-resolved spectroscopy and analysis of decay kinetics we determine the nature of the interaction and we show the existence of chromium-thulium pairs in which the chromium emission wavelength is shifted from 693.6 to 694 nm.     

High pressure and time resolved luminescence spectra of Gd3Ga5O12:Pr crystal

Luminescence spectra and time resolved luminescence spectra of GGG crystal doped with Pr³⁺ were measured at high hydrostatic pressure from ambient to 220 kbar. Effect of pressure results in the red shift of all luminescence lines related to Pr³⁺ ion emission equals from −0.32 to −1.02 cm⁻¹/kbar and in the diminishing of the luminescence lifetimes. The luminescence decay related to emission from ³P₀ state was single-exponential and diminished with pressure from 23 μs at ambient pressure to 6.5 μs at 165 kbar. Luminescence decay related to transition form ¹D₂ state was two-exponential with longer decay equal to 162 μs at ambient pressure and 120 μs at 165 kbar. We discussed effect of pressure on the ¹D₂ → ³H₄ luminescence and emission from ³P₀ state in the context of non-radiative processes that depopulate the ³P₀ and populate the ¹D₂ state, considering mainly multiphonon relaxation processes and depopulation via the praseodymium trapped exciton state.     

Crystal growth and characterization of Yb-doped Gd3Ga5O12

Single crystals of (Yb_xGd_1−x)₃Ga₅O₁₂ (0.0 ≤ x ≤ 1.0) have been grown by the micro-pulling-down method. Formation of continuous solid solutions with a garnet structure was confirmed. Composition dependence of the lattice constant, thermal diffusivity, specific heat capacity and thermal conductivity was investigated. Assignment of the Yb³⁺-energy levels in Gd₃Ga₅O₁₂-host lattice has been performed by using absorption, emission and Raman spectroscopy measurements at both, room temperature and at 12 K.     

Comparison of Bi3Fe5O12 film giant Faraday rotators grown on (111) and (001) Gd3Ga5O12 single crystals

Bismuth iron garnet (Bi₃Fe₅O₁₂, BIG) epitaxial thin films were grown on single crystal (Gd₃Ga₅O₁₂, GGG) (111) and (001) substrates by rf-magnetron sputtering technique. Processing parameters have been optimized to obtain high deposition rate (2.74 μm/h) and the surface rms roughness less than 10 nm. X-ray diffraction reveals films epitaxial quality: exclusive (111) or (001) orientation with narrow rocking curves and strong in-plane texture. Films possess low optical loss and magneto-optical Faraday rotation (FR) as high as 5 deg/μm at 677 nm wavelength. Comparative analysis of films grown on (111) and (001) substrates clearly shows significant superiority of BIG/GGG(001) film. For this film, the coercive field ∼100 Oe appears to be 2.5 times lower while the optical transmission to be 10% higher than that for BIG/GGG(111) film. Enhanced magneto-optical performance of BIG/GGG(001) films relies upon better accommodation of the film-to-substrate mismatch strain through the tetragonal BIG lattice distortions compared to the rhombohedral one in BIG/GGG(111) films.     

Nd optical multisites in the Ca3(Nb,Ga)2Ga3O12 laser garnet crystal

Laser excited site-selective luminescence of Nd³⁺ ion in the Ca₃(Nb,Ga)₂Ga₃O₁₂ garnet crystal has been investigated for the and transitions. Six main non-equivalent crystal field sites were detected in the garnet. The crystal splitting scheme of the and manifolds was obtained for each Nd³⁺ site. Energy transfer between Nd³⁺ sites was observed by using time resolved spectroscopy.     

Gd3(Al,Ga)5O12:Ce闪烁晶体扭曲生长、组分偏析与性能研究

新型闪烁晶体Gd3(Al,Ga)5O12:Ce(简写为GAGG:Ce)在制备过程中易出现多晶扭曲生长、组分偏析等问题,严重影响晶体的性能.为了得到大尺寸高质量的GAGG:Ce晶体,采用X射线衍射(XRD)、电感耦合等离子体发射光谱(ICP-OES)和X射线激发发射谱(XEL)等手段,结合熔体特性分析了GAGG:Ce晶体...     

Splitting and broadening of the emission bands of Y2O3:Eu3+,Nd3+ and its dependence on Nd3+ concentration and annealing temperature

Although Eu³⁺ ion-doped Y₂O₃ has been extensively used as red phosphors, their color rendering needs to be improved for high-quality illumination and displaying. Here, we show that the emission spectra of Y₂O₃:Eu³⁺ red phosphors can be broadened by the doping of Nd³⁺ ion so that the color rendering capability of Y₂O₃:Eu³⁺ was remarkably enhanced. Y₂O₃:Eu³⁺ and Y₂O₃:Eu³⁺,Nd³⁺ colloidal spheres were synthesized by wet chemical procedure and high-temperature treatment. The fluorescence measurement under the 254 and 380 nm ultraviolet excitation indicates that the 612 nm red emission peak of Eu³⁺ can be splitted into two ones by the doping of Nd³⁺ ion, of which the full width at half maximum (FWHM) is broadened from 4.2 nm to 9.6 nm. By varying the concentration of Nd³⁺ ion, it was determined that the optimal doping concentration of Nd³⁺ ion is of 3 mol% for realizing the strongest emission intensity. The further increase of Nd³⁺ ion exceeding 3 mol% would lead to a concentration quenching phenomenon. The analysis based on XRD spectra and the simplified energy diagram suggested that the doped Nd³⁺ ion not only monitored the growth dynamics, but also took an efficient energy transfer and a cross relaxation process to generate intense emission from Eu³⁺ ion in both of C₂ and S₆ sites, instead of preferable one type of Eu³⁺ site (C₂ or S₆) in the Nd³⁺ undoped sample.     

Time-resolved spectroscopy of intrinsic luminescence of Y3Ga5O12 and (LaLu)3Lu2Ga3O12 single crystals

The nature of intrinsic luminescence of Y₃Ga₅O₁₂ (YGG) and (LaLu)₃Lu₂Ga₃O₁₂ (LLGG) single crystals grown from a melt was determined. In the case of a YGG single crystal containing Y_Ga antisite defects with a concentration of 0.25–0.275 at.% the intrinsic luminescence was considered as a superposition of luminescence of self-trapped excitons (STE), luminescence of excitons localized near antisite defects (LE(AD) centers) and luminescence caused by a recombination of an electron with a hole captured at Y_Ga antisite defects. Due to a large (2–3%) concentration of Lu_La antisite defects in LLGG single crystals the intrinsic luminescence was a superposition mainly of the LE(AD) center emission and the recombination luminescence of Lu_La antisite defects. The energy structure of the mentioned centers in YGG and LGGG hosts was determined from the excitation spectra of their luminescence under excitation by synchrotron radiation in the range of the fundamental absorption edge of these garnets.     

Thermal expansion studies of Gd2Mo3O12 and Gd2W3O12

Simultaneous thermogravimetric/differential thermal analysis of Gd₂Mo₃O₁₂ showed an irreversible phase transition at 1178 K where as Gd₂W₃O₁₂ showed reversible phase transition at 1433 K, which were confirmed by powder X-ray diffraction. The thermal expansion behavior of α-Gd₂Mo₃O₁₂ (room temperature phase), β-Gd₂Mo₃O₁₂ (phase obtained by heating Gd₂Mo₃O₁₂ at 1223 K) and Gd₂W₃O₁₂ have been investigated using high temperature X-ray diffractometer. The cell volume of α-Gd₂Mo₃O₁₂, β-Gd₂Mo₃O₁₂ and Gd₂W₃O₁₂, fit into polynomial expression with respect to temperature, showed positive thermal expansion up to 1073, 1173 and 1173 K, respectively. The average volume expansion coefficients for α-Gd₂Mo₃O₁₂, β-Gd₂Mo₃O₁₂ and Gd₂W₃O₁₂ are 39.52 × 10⁻⁶, 21.23 × 10⁻⁶ and 37.96 × 10⁻⁶ K⁻¹, respectively.     

Luminescent properties of GdAl3(BO3)4:Ln3+ (Ln3+:Eu3+, Tb3+, Dy3+) nano-phosphors

GdAl₃(BO₃)₄:Ln³⁺ (Ln³⁺:Eu³⁺, Tb³⁺, Dy³⁺) nano-phosphors were prepared by sol–gel method. The structure properties of the phosphors are characterized by XRD, and GdAl₃(BO₃)₄:Ln³⁺ nano-phosphors have average sizes around 40 nm. The doping concentrations of Eu³⁺, Tb³⁺ and Dy³⁺ ions in GdAl₃(BO₃)₄ nano-phosphors are from 1 to 9 mol% for Eu³⁺ ions, from 2 to 12 mol% for Tb³⁺ ions and from 1 to 5 mol% for Dy³⁺ ions, respectively. The luminescent properties of rare-earth ions doped GdAl₃(BO₃)₄ nano-phosphors are analyzed by the photoluminescence spectra, which prime doping concentration of Eu³⁺, Tb³⁺, and Dy³⁺ ions are at 5, 12 and 3 mol%, respectively. The energy transfers in the luminescent processes of rare-earth ions doped GdAl₃(BO₃)₄ nano-phosphors are discussed.