载体MCM-41对Tb（aspirin）3phen发光性能的影响

在室温下,乙二胺环境中合成了高度有序的介孔材料MCM-41,并将经热处理的发光客体Tb(aspi-rin)3phen组装进其孔道,通过激发发射光谱对其光致发光性能进行了研究。结果表明,Tb(aspirin)3phen240～375 nm区间的宽激发峰归属于配体aspirin羰基n→π*跃迁、苯环π→π*跃迁,和phen的杂菲基团吸收,Tb3 的特征发射是由于Antenna效应引起的。相对于纯Tb(aspirin)3phen,Tb(aspirin)3phen-MCM-41B和Tb(aspirin)3phen/MCM-41A的激发谱带出现了明显的分裂,而Tb(aspirin)3phen-MCM-41A只在353nm处剩下了相对较窄的单峰。Tb(aspirin)3phen-MCM-41B,Tb(aspirin)3phen/MCM-41A和Tb(aspirin)3phen-MCM-41A的短波段激发峰依次减弱消失,长波段激发峰逐渐增强,而405 nm发射峰强度IL和544 nm发射峰强度ILn的比值I(I=IL/ILn)依次减小。MCM-41骨架与Tb(aspirin)3phen成键后,不同程度降低了配体aspirin和phen单重态S1和三重态T1能级,且对phen的影响大于aspirin。不同的MCM-41表面晶格场对配体能级的影响顺序为:MCM-41B外表面>MCM-41A外表面>MCM-41A内表面。I值可定性表示MCM-41表面晶格场对配体能级影响程度和MCM-41表面Tb(aspirin)3phen的含量。     

有机-无机杂化材料Eu(BA)3-MCM-41的制备及光学性质

将稀土有机配合物Eu(BA)3组装进介孔MCM-41中,得到有机-无机杂化介孔材料Eu(BA)3-MCM-41。采用XRD、IR、激发、发射光谱等测试方法对其结构和性能进行了分析。结果表明,组装体保持了有序的介孔骨架结构,由组装体IR谱图中波数3451cm-1吸收峰的消失及970cm-1吸收峰强度的降低可知,介孔中Eu(BA)3的引入使得配合物自身含有的结晶水、MCM-41中的吸附水和羟基数目减少,由于Eu(BA)3与—OH在介孔孔道中成键使羟基减少,降低了Eu3 的发光猝灭效应,提高了Eu3 的发光效率。组装体中主客体之间存在较强的相互作用,MCM-41的存在使Eu(BA)3对激发光有更强吸收,且使Eu(BA)3-MCM-41的发光强度较Eu(BA)3有显著的提高。     

介孔组装体Alq3-MCM-41的光学性质

将有机发光小分子8-羟基喹啉铝(Alq₃)组装进介孔MCM-41中,采用XRD、IR、荧光光谱等测试方法对组装体Alq₃-MCM-41进行表征。XRD表明,Alq₃-MCM-41保持了有序的介孔骨架结构;IR谱图中,在波数1542 cm^-1处出现的特征吸收谱带表明组装体中Alq₃在孔道中与羟基成键;荧光光谱表明,组装体中MCM-41与Alq₃分子间发生了能量转移,从而使Alq₃-MCM-41具有优异的发光性能;荧光强度随组装量的增多而显著增强,这主要是由于在Alq₃-MCM-41中,MCM-41有序孔道的微环境使Alq₃分子分散性提高,减弱了Alq₃分子间的聚集或缔合现象,从而有效地提高了其发光强度。     

(纳米MCM-41)-CdS主-客体复合材料的制备及光学性质

以水热法制备了纳米微粒MCM-41分子筛，通过离子交换法将Cd(II)交换到分子筛中，然后采用硫代乙酰胺作硫化氢前驱体对(MCM-41)-Cd进行硫化，制备出主-客体复合材料(MCM-41)-CdS．化学分析表明，客体成功地组装到分子筛中．粉末X射线衍射结果表明，组装过程并未破坏所制备的主-客体材料中分子筛的骨架，分子筛骨架完整且结晶度仍然很高．红外光谱表明所制备材料骨架保持完好．低温N2吸附-解吸附研究表明，相对于MCM-41分子筛主体所制备的复合材料孔体积、孔尺寸及比表面积降低，表明客体在分子筛孔道内组装成功．制备的主-客体复合材料固体扩散漫反射吸收光谱相对于CdS体相呈现某些蓝移，说明客体处于分子筛孔道内，也表明分子筛主体对纳米硫化镉客体表现出明显的立体限域效应．(纳米MCM-41)-CdS及(微米MCM-41)-CdS样品呈现明显发光．     

BaMgF_4:Er~(3+),Yb~(3+)上转换纳米晶的合成及其发光性能研究

采用反向共沉淀法制备了形貌呈棒状的BaMgF4:Er3+,Yb3+上转换纳米晶.样品在980 nm半导体激光器激发下发射绿色和红色上转换荧光,其发射的绿、红发射带归因于Er3+离子的2H11/2—4I15/2,4S3/2—4I15/2和4F9/2—4I15/2跃迁.当Er3+的掺杂浓度为3%,Yb3+离子掺杂浓度为10%时,荧光粉的上转换发光强度最强;随着Yb3+离子浓度的增加样品的红光发射增强,绿光发射减弱.通过上转换发光强度与抽运电流关系曲线的拟合,得出BaMgF4:Er3+,Yb3+上转换材料的绿光与红光的上转换过程均为双光子吸收过程.     

下转换材料β-NaYF4:Tb3+,Yb3+的水热法合成和发光性质研究

利用水热法合成了粉末发光材NaYF4:Tb3+,Yb3+分别用X射线衍射(XRD),光致发光谱(PL)和激发谱(PLE)测试了合成材料的物相结构和发光性质.研究结果表明:合成的NaYF4:Tb3+,Yb3+抖材料为六方相的品体,无立方相的.改变Tb3+和Yb3+的掺杂浓度后品格结构没有变化,说明离子Tb3+和Yb3+取...     

稀土离子掺杂的AlF3基氟化物玻璃

在800和970!nm LD激发下,分别研究了Er3+单掺和Yb3+,Tm3+共掺的AlF3基(AYF,AZF)玻璃中上转换发光、能量传递和浓度猝灭.在Er3+掺杂的AlF3基玻璃,随着Er3+掺杂量的增加,红光与绿光上转换发光强度比(Ired/Igreen)增加,这被认为与两个Er3+离子(一个在4I9/2态、另一个在4S3/2态)的交叉弛豫过程有关.在Tm3+-Yb3+共掺的AlF3基玻璃中,发现对于Tm3+的浓度猝灭,蓝光跃迁比近红外荧光跃迁表现更明显,研究还发现Yb3+-Tm3+共掺AYF和AZF玻璃存在Yb3+离子对上转换发光的猝灭现象,这被认为可能是Tm3+(3F4)→Yb(3F5/2)反向能量传递的结果.     

Na_4Ca_4Al_6Si_9O_(24)∶Ce~(3+),Tb~(3+)荧光粉合成及其能量传递研究（英文）

天然方柱石是一种典型的硅酸盐类的发光矿石,针对天然高发光效率方柱石的生成条件及化学成份,采用高温固相法在1 100℃弱还原气氛下合成了Na4Ca4Al6Si9O24(方柱石),并合成了一系列掺杂Ce3+,Tb3+的荧光粉,对其晶体结构做了讨论。通过分别对单掺Ce3+,Tb3+和共掺Ce3+,Tb3+样品发光性质的研究,发现共掺杂的样品其在545nm处由于Tb3+的5 D+4→7 F5跃迁发光强度远远大于单掺Tb3的样品。最后通过掺杂不同浓度Ce3+样品发光性质的研究,以及其荧光寿命和能量传递机理分析,结果表明随着Ce3+掺杂浓度的变化,样品的Tb3+的5 D7 4→F5跃迁(545nm)发光强度及寿命也随着变化,并发现Ce3+对Tb3+存在能量传递,且当Ce3+和Tb3+的质比为0.02∶0.03时能量传递效率最高。通过色坐标的测量,发现随着Ce3+浓度的改变,样品的发光可在绿色区域进行调节。因此,认为Na4Ca4Al6Si9O24∶Ce3+,Tb3+荧光粉有望成为新型白光LED荧光粉。     

ZBLAN玻璃中Nd~(3+),Tm~(3+),Yb~(3+)的上转换发光特性

采用高温固相法制备了Nd,Tm和Yb掺杂的ZBLAN玻璃上转换材料.Tm3+,Yb3+的摩尔浓度分别固定为0.01%,0.3%,Nd3+摩尔浓度变化范围为0.1%～2%.在室温下,测试了样品在300～1 000nm间的吸收光谱.在798 nm近红外光激发下,测试了样品的上转换光谱.实验发现,样品在798 nm红外光激发下发出了较强的多波段(红,蓝和绿)的可见光.由上转换可见光各波段的发射谱线,给出了能级跃迁机制.蓝光主要来源于Tm3+的激发态1G4到基态3H6的跃迁,绿光来源于Nd3+的2H7/2到基态4I9/2的跃迁,红光来源于Nd3+的2H11/2到基态4i9/2的跃迁.研究发现,在Nd3+,Tm3+,Yb3+:ZBLAN玻璃样品中存在激发态吸收,能最转移和交叉弛豫等上转换过程.其发光机理是Nd3+,TM3+和Yb3+离子之间的能量转移.根据Nd3+摩尔浓度不同其上转换发光强度不同,分析了掺入稀土的浓度对上转换发光效率的影响.当Nd3+浓度为1.5%(摩尔分数)时上转换发光最强,大于1.5%后发光开始减弱.     

Yb3+掺杂浓度对Er3+/Yb3+共掺SiO2-Al2O3-La2O3玻璃光谱性质的影响

测量了不同Yb3+ 离子掺杂浓度下 ,Er3+ /Yb3+ 共掺SiO2 Al2 O3 La2O3玻璃的吸收光谱、荧光光谱和Yb3+离子2 F5/ 2 的能级寿命 ,应用迈克康伯 (McCumber)理论计算了Er3+ 的受激发射截面σemi,讨论了Yb3+ 离子浓度对其自身吸收性质、Er3+ 离子发光性质 ,以及Yb3+ →Er3+ 能量传递效率 (η)的影响 ,初步探明该基质玻璃中Yb3+ 离子掺杂数浓度的最佳范围为 3 .94× 1 0 2 0 cm- 3至 5 .92× 1 0 2 0 cm- 3,在此掺杂范围内 ,Yb3+ 离子的最大吸收系数为9.8cm- 1 ,Er3+ 的峰值发射截面和Yb3+ →Er3+ 能量传递效率 (η)分别为 0 64× 1 0 - 2 4 m2 和 92 %。     

Effects of Li~+ on photoluminescence of Sr_3SiO_5:Sm~(3+) red phosphor

The structure and photoluminescence (PL) properties of Sr3SiO5 : Sm3+ and Li+-doped Sr3SiO5 : Sm3+ red-emitting phosphors were investigated. Samples were prepared by the high-temperature solid-state method. PL spectra show that the concentration quenching occurs when the Sm3+ concentration is beyond 1.3 mol% in Sr3SiO5 : Sm3+ phosphor without doping Li+ ions. The concentration-quenching mechanism can be explained by the electric dipole-dipole interaction of Sm3+ ions. The incorporation of Li+ ions into Sr3SiO5 : Sm3+ phosphors, as a charge compensator, improves the PL properties. The lithium ions also suppress the concentration quenching in Sm3+ with concentration increased from 1.3 mol% to 1.7 mol%.     

0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3单晶/环氧树脂1-3型复合材料的压电性能研究

模拟了0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃(PMN-0.3PT)单晶1-3型压电复合材料的性能与单晶体积分数的关系，得出性能最优时压电相的体积分数为64%, 在这一体积分数下，采用切割-填充法，并使用了不同类型的环氧树脂填充制备复合材料.系统地研究了聚合物相对复合材料性能的影响，研究表明，减小聚合物相的刚度系数c和密度ρ有利于提高复合材料的性能，且聚合物相与压电相的结合强度对性能的影响非常明显，制备的PMN-0.3 PT单晶1-3型复合材料的厚度伸缩机电耦合系数k_t高达90.1%，压电系数d₃₃大于1000pC/N，机械品质因数Q_m为10.39，声阻抗Z也大大降低，性能明显优于传统的Pb(Zr_xTi_1-x)O₃(PZT)陶瓷及其1-3复合材料，在压电换能器和传感器中显示出广阔的前景. 关键词： PMN-PT单晶 压电复合材料 压电相 聚合物相     

Influence of atmospheric exposure of tris (8-hydroxyquinoline) aluminum (Alq<Subscript>3</Subscript>): a photoluminescence and absorption study

We have investigated the effects of atmospheric exposure on the properties of tris (8-hydroxyquinoline) aluminum (Alq₃) thin films by photoluminescence (PL) and UV-Vis absorption measurements. Alq₃ films were evaporated on glass substrates at different temperatures. The influence of annealing on the environmental stability of the films has also been investigated. It has been found that deposition at higher substrate temperature and annealing of the samples deposited at room temperature yield an improvement in the environmental stability of the films, i.e. less decrease in the PL intensity over time with exposure to atmosphere, as well as increased PL intensity. To investigate further the effects of the air exposure, films deposited at room temperature were stored for four days in air, nitrogen, and oxygen. No decrease in PL intensity has been found for storage in nitrogen, while the decrease for the film stored in oxygen was smaller than that for the film stored in air, indicating that both humidity and oxygen play a role in the PL intensity decrease in Alq₃ thin films. PACS 78.55.Kz; 78.40.Me     

Low-temperature sintering and electromagnetic properties of Ba(Zn1/3Nb2/3)O3/NiCuZn ferrite composites

Dense Ba(Zn_1/3Nb_2/3)O₃/(Ni_0.37Cu_0.20Zn_0.43O)-(Fe₂O₃)_0.96 (BZN/NiCuZn) composites were prepared by the conventional solid-state reaction method and sintered at 950 °C. The phase composition and surface morphology of the composites were investigated using XRD and SEM, respectively. The dielectric and magnetic properties of the composites are also reported. In low frequency range the dielectric properties of the BZN/NiCuZn composites show Maxwell-Wagner relaxation. In high frequency range the BZN/NiCuZn composites possess high dielectric constants and permeabilities, which can be used in high-frequency communications for capacitor-inductor integrating devices such as electromagnetic interference filters and antennas.     

Effect of H_3BO_3 on the phase stability and long persistence properties of Sr_(3.96)Al_(14)O_(25):Eu_(0.01)~(2+), Dy_(0.02)~(3+) phosphor

Sr3.96Al14O25:Eu2+ ,Dy3+ long persistent materials with different weights of H3BO3 prepared by the high temperature solid-state reaction method were characterized by X-ray powder diffraction (XRD), scanning electronic microscopy (SEM), photoluminescence spectra (PL), and thermoluminescence (TL). The results of XRD indicate that the 3% addition of H3BO3 favorable for the formation of pure phase Sr4Al14O25 , and SrAl12O19 was generated when there is a low content or high content of H3BO3 . The average grain sizes of samples grow bigger with an increase of H3BO3 . PL spectra show that the emission peak does not shift evidently and the emission intensity changes little, indicating that the different amount of H3BO3 has little influence on the crystal field. The decay characteristics and TL measurement show that H3BO3 affects the afterglow properties of Sr3.96Al14O25 :Eu2+ ,Dy3+ , because the increasing H3BO3 leads to more defects in the Sr4Al14O25 matrix.     

Spectral investigation of R,Ce:YAG(R: Pr~(3+), Eu~(3+), Gd~(3+)) single crystals and their applications in white LEDs

Eu3+, Pr3+, or Gd3+codoped Ce:YAG single crystals were grown by using the Czochralski method. The photoluminescence(PL) emission and excitation spectra and transmittance were measured and investigated. The additional red-emitting bands were observed in the PL emission spectra of Eu,Ce:YAG and Pr,Ce:YAG single crystals and the formation of noticeable peaks was studied with reference to the schematic energy level diagrams. A red-shifted phenomenon was observed in the PL emission spectrum of Gd,Ce:YAG. With codoped Eu3+, Pr3+, or Gd3+ions, warmer white light was achieved for the white light emitting diodes and the color rendering index became higher.     

g-C3N4 modified Bi2O3 composites with enhanced visible-light photocatalytic activity

Novel g-C₃N₄ modified Bi₂O₃ (g-C₃N₄/Bi₂O₃) composites were synthesized by a mixing-calcination method. The samples were characterized by thermogravimetry (TG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), UV–vis diffuse reflection spectroscopy (DRS), photoluminescence (PL) and photocurrent-time measurement (PT). The photocatalytic activity of the composites was evaluated by degradation of Rhodamine B (RHB) and 4-chlorophenol (4-CP) under visible light irradiation (>400 nm). The results indicated that the g-C₃N₄/Bi₂O₃ composites showed higher photocatalytic activity than that of Bi₂O₃ and g-C₃N₄. The enhanced photocatalytic activity of the g-C₃N₄/Bi₂O₃ composites could be attributed to the suitable band positions between g-C₃N₄ and Bi₂O₃. This leads to a low recombination between the photogenerated electron–hole pairs. The proposed mechanism for the enhanced visible-light photocatalytic activity of g-C₃N₄/Bi₂O₃ composites was proven by PL and PT analysis.     

不同玻璃组分对β-NaYF4:Yb3+,Er3+/Tm3+粉体的侵蚀性研究及对发光性能的影响

选用硅酸盐、硼酸盐以及磷酸盐3种常用的玻璃体系,与β-NaYF₄:Yb³⁺,Er³⁺/Tm³⁺粉体均匀混合压片后在不同的温度(400～700 ℃)下进行热处理。采用X射线衍射技术和荧光光谱技术等测试手段研究不同玻璃形成体以及碱金属离子对β-NaYF₄:Yb³⁺,Er³⁺/Tm³⁺粉体的侵蚀情况以及对发光性能的影响。研究结果表明,在硼酸盐玻璃体系与β-NaYF₄:Yb³⁺,Er³⁺/Tm³⁺粉体复合热处理过程中,Li⁺和K⁺离子会取代β-NaYF₄晶体中Na原子的位置。 在相同热处理温度下,不同玻璃体系与β-NaYF₄晶体反应剧烈程度:磷酸盐>硼酸盐>硅酸盐。     

Dy~(3+),Sm~(3+)共掺杂Ca_2A1[AlSiO_7]荧光粉的发光性质研究

采用高温固相反应法合成了一系列Dy~(3+)、Sm~(3+)单掺杂和共掺杂铝方柱石发光材料,详细地研究了Dy~(3+)、Sm~(3+)掺杂对铝方柱石的结构和发光性质的影响。XRD结果表明Dy~(3+)、Sm~(3+)离子单掺杂和共掺杂样品均形成了单相的铝方柱石结构化合物,并没有改变基质的晶体结构。发光光谱表明,通过调节Dy~(3+)、Sm~(3+)离子的掺杂比例,发光颜色可实现从黄色到黄白色的可控调节。此外,发射和激发光谱表明,Dy~(3+)与Sm~(3+)离子之间存在有效的光谱重叠,暗示着Dy~(3+)→Sm~(3+)的能量传递。荧光寿命衰减结果进一步证实Dy~(3+)与Sm~(3+)离子之间是一种无辐射共振能量传递方式。     

Piezoelectric cement-based 1-3 composites

This paper presents a new functional material for smart structure applications. Piezoelectric PZT/cement 1-3 composites that have good compatibility with civil engineering structural materials have been studied. The composites with different volume fractions of PZT ranging from 0.25 to 0.77 were fabricated by the dice-and-fill method. It was found that the 1-3 composites have good piezoelectric properties that agreed quite well with theoretical modeling. The thickness electromechanical coupling coefficient could reach 0.55 in the composite with a ceramic volume fraction of 0.25. Those composites have potential to be used as sensors in civil structure health monitoring systems. PACS 77.65.-j; 77.84.Lf