硼酸掺量对SrAl2O4长余辉发光材料的发光性能影响

用燃烧法制备了Eu2 ,Dy3 共掺杂SrAl2O4长余辉发光材料,研究了不同硼酸掺量对Eu2 ,Dy3 共掺杂SrAl2O4长余辉发光材料发光性能的影响。为了分析B2O3在材料制备中的作用,用XRD对所合成材料进行物相分析,用荧光光谱仪记录其发射光谱,并在暗室里拍摄紫外激发下的发光照片。结果表明:硼酸掺量为0.8的样品的发光光谱,其发射峰峰值位于518 nm,是典型的Eu2 的4f5d→4f的特征发射,为一宽谱带发光光谱。硼酸掺量为2的样品的发光光谱,其在518 nm位置的峰十分弱,而在487 nm处同时出现了一个弱峰,整个谱线呈一斜坡状。随着硼酸加入量的不同,Eu2 ,Dy3 共掺杂铝酸锶的发光效果、形貌特征均不同。在某一范围内,随着硼酸添加量的增加,合成了发光主晶相,烧结温度有所降低,材料的发光性能和发光亮度均有所提高。     

铝酸锶铕镝磷光体及其发光特性研究

用燃烧法在６００℃合成了铝酸锶铕及铝锶铕镝磷光体并测定了其激光光谱、发射光谱及长余辉性质。结果表明,铝酸锶铕镝更适宜于制备长余辉材料,而铝思铕适宜于制作瞬时激发－－发光材料。     

复合氟化物中缺陷对Eu2+光谱的影响

用传统的高温固相法及近几年兴起的温和水热法合成了KMgF3:Fu多晶粉末，同时用BridgmanStockbarger法生长了KMgF3:Eu单晶体。对三种方法合成的样品进行比较发现：水热和单晶样品中，除了Eu^2 的f→f锐线发射外，还观察到420nm处的宽带发射；这些发射带主要应归属于晶体中存在的色心和氧中心。而且与高温样品相比，Eu^2 在360nm处的线发射强度明显减小，原因是发生了Eu^2 到色心的能量传递。     

Pulse-induced mechanoluminescence of ultraviolet-irradiated SrAl2O4:Eu,Dy phosphors

The SrAl₂O₄:Eu,Dy phosphors prepared by solid state reaction technique in a reduced atmosphere of 95% Ar+5% H₂ exhibit very intense mechanoluminescence (ML) which can be seen in daylight with naked eye. When the phosphors are deformed by the impact of a low-power electric hammer, initially the ML intensity increases with time, attains a maximum value and then decreases with time. After the threshold pressure, the peak of ML intensity I_m and the total ML intensity I_T increase with the increasing value of the impact pressure. For the ML excited by the pressure pulse of short duration, two decay times of ML are observed; however, for the ML excited by the pressure pulse of long duration, only one decay time is observed. The ML intensity decreases with successive applications of pressure on SrAl₂O₄:Eu,Dy phosphors. For the low applied pressure in the range below the limit of elasticity recovery of ML intensity takes place when the sample is exposed to ultraviolet (UV) light. This fact indicates that the vacant traps produced during the application of pressure pulses get filled during the exposure of the sample to UV light. The ML in the elastic region of SrAl₂O₄:Eu,Dy phosphors can be understood on the basis of the piezoelectrically induced detrapping model. The non-irradiated SrAl₂O₄:Eu²⁺,Dy³⁺ phosphors exhibit ML during the fracture of the compact mass of phosphors whose ML intensity is less when compared to that of the UV-irradiated compact masses. The ML induced by pressure pulses may be useful for determining the magnitude and rise time of unknown pressure pulses and to determine the lifetime of charge carriers in shallow traps.     

SrAl2O4:Eu2+,Dy3+的上转换发光特性

铕镝共掺的铝酸锶是一种新型的绿色长余辉荧光材料 ,经可见 -紫外光激发后 ,能发出超长时间的余辉。本文首次用 980nm的红外激发光源激发SrAl2 O4 :Eu2 ,Dy3 磷光体后 ,在室温下观测到了SrAl2 O4 :Eu2 ,Dy3 的绿色上转换荧光。并测得了其上转换荧光光谱图。与其正常的荧光光谱图相比 ,两者的峰形及波峰的位置有很大的差异 ,这预示着两者有不同的发光机理 ,并就其发光机理进行了初步的探讨。所用的样品经高温固相法合成后 ,用XRD表征。两种荧光光谱用荧光光谱仪测定。     

自蔓延高温合成掺杂SrAl2O4稀土长余辉发光粉的研究

在600℃下用自蔓延高温法制备了SrAl2O4∶Eu2+0.012 5,RE3+0.012 5(RE3+=Ce3+,Pr3+,Nd3+,Tb3+,Dy3+),SrAl2O4∶Eu2+0.012 5,M0.012 5(M=Li+,Be2+,Cd2+,Mn2+,Cu2+,Ag+,Zn2+,pb2+),SrAl2O4∶Eu2...     

Eu,Dy共掺杂SrAl2O4长余辉材料制备新工艺

活化Al-Sr合金粉末水解制备SrAl₂O₄长余辉材料的前驱体,并采用高温固相反应法制备出Eu,Dy共掺杂的SrAl₂O₄长余辉材料,对其微观结构和发光特性进行了研究。实验结果表明:前驱体中Al、Sr元素在微观状态下分布均匀,所制成的长余辉发光材料的发射主峰位于520nm附近,为典型的Eu²⁺离子4f5d-4f的特征发射,初始亮度达到18cd/m²,余辉时间长达46h。     

Raman analyses of co‐phasing and hysteresis behaviors in V2O3 thin film

We present the studies of the phase transition behaviors of V₂O₃ thin film using temperature‐dependent Raman scattering spectroscopy. Our results show that in both the cooling and heating processes of V₂O₃ thin film, the phase transition occurs gradually but not suddenly, contrary to that in single crystal. The coexistence of both the metal and insulator phases with co‐phasing ΔT_c larger than 30 K is observed in both the cooling and heating processes. We discuss that this large co‐phasing ΔT_c should be distinguished with the large hysteresis ΔT_h reported in nanostructures. In addition, our discussions indicate that co‐phasing ΔT_c and hysteresis ΔT_h would be mainly correlated with stress and defect states in sample, respectively. Furthermore, our Raman analyses suggest that stress would also induce phase transitions in V₂O₃, and the stress (pressure)‐induced phase transitions would behave differently comparing with the temperature‐induced transitions under normal pressure. Copyright © 2012 John Wiley & Sons, Ltd.     

SrAl12O19:Pr3+中4f2→4f2电偶极跃迁强度参量化

对SrAl12O19:Pr3+中4f2→4f2电偶极跃迁强度的参量化进行了研究.考虑明确的4f5d组态成分与4f2跃迁能级混杂对4f2组态内跃迁的影响.引入新的强度参数Tkq,参数值由3P0能级的相关实验数据拟合.利用拟合的参数T33和T53计算1S0向下各能级发射的跃迁强度,计算值与实验及Judd-Ofelt理论的结果进行了比较.     

Electrochemical reduction of 3‐phenyl‐1,2‐benzisoxazole 2‐oxide on boron‐doped diamond

The bioreduction of N‐oxide compounds is the basis for the mode of action of a number of biologically active molecules. These compounds are thought to act by forming a reactive oxygen species through an intracellular reduction and subsequent redox cycling process within the organism. With these results in mind, the preliminary investigation into the electrochemical reduction of the benzisoxazole 2‐oxide ring system was undertaken, with the thought that this class of compounds would reduce in a similar fashion to other N‐oxide heterocycles. The electrochemical reduction of 3‐phenyl‐1,2‐benzisoxazole 2‐oxide on boron‐doped diamond was studied using cyclic and square wave voltammetry as well as controlled potential electrolysis and HPLC for qualitative identification of the reaction products. It was found that the reduction proceeded with an initial quasi‐reversible one‐electron reduction followed by the very fast cleavage of either the endocyclic or exocyclic N–O bond. Subsequent electron transfer and protonation resulted in an overall two‐electron reduction and formation of the 2‐hydroxyaryl oxime and benzisoxazole. These results are analogous to those observed in the electrochemical reduction of other heterocyclic N‐oxides albeit the reduction of the benzisoxazole N‐oxides takes place at a more negative potential. However, these encouraging results warrant further investigation into the reduction potential of substituted benzisoxazole N‐oxides as well as to elucidate and characterize the nature of the intermediate species involved. Copyright © 2014 John Wiley & Sons, Ltd.     

激光微区发射光谱分析法测定铝酸锶铕镝长余辉材料中的铕

激光微区发射光谱分析法结合CCD光学多道分析仪测定了SrAl2O4:Eu2 ,Dy3 长余辉材料中铕的含量,研究了该方法用于长余辉材料定量分析的准确性。实验中以Eu(Ⅱ)412.973nm为分析线,计算机拟合LogIf~Logc工作曲线,对Eu的分析结果表明:分析谱线相对强度RSD为4.3%,定量分析相对标准偏差RSD为7.4%,分析结果的平均值为2.13%;采用高温固相反应法制备SrAl2O4:Eu2 ,Dy3 长余辉材料,制备前后的Eu百分含量发生明显变化,高温合成后的长余辉材料中Eu百分含量明显增大。     

Influence of the dopant type on point defects in PbMoO4 crystals

Nominally pure and Nd³⁺-doped single crystals of PbMoO₄ grown by the Czochralski method with the use of Nd₂O₃, Nd₂(MoO₄)₃, NaNd(MoO₄)₂, and NdNbO₄ compounds are investigated by the methods of single-crystal and powder X-ray diffraction analysis, single-crystal neutron diffraction, and impedance spectroscopy. The types and concentration of point defects are determined. Their effect on the dielectric properties of crystals is hypothesized. It is established that the color of the crystals is caused by the formation of color centers.     

Influence of a metal surface on the luminescence of adsorbed europium compounds

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 6, pp. 130–134, November–December, 1995.     

Influence of dopant level on structural, optical and magnetic properties of Co-doped anatase TiO2 nanoparticles

Cobalt-doped TiO₂ nanoparticles were synthesized by sol-gel method. The associated structural, optical, compositional and magnetic properties of the nanoparticles as a function of cobalt concentration have been systematically studied. The X-ray powder diffraction reveals that all samples have pure anatase phase tetragonal system and the lattice parameter analysis indicated that Co ions may substitute into the lattice of TiO₂. The average particle size is 15 nm, when found through transmission electron microscope. Optical spectroscopy measurement showed that the bandgap value decreases upon increasing Co concentration. The magnetic measurements revealed that the enhanced room temperature ferromagnetism (RTFM) strongly depends on the doping content.     

Tm3+掺杂SrAl2O4:Eu2+的光激励和热释光性能

通过高温固相法制备出Sr_{0.98-xAl2O4:0.02Eu²⁺,xTm³⁺(x=0,0.01,0.02,0.03,0.04,0.05)系列样品,并对其光激励和热释光性能进行了研究。在SrAl2O4:Eu²⁺原有陷阱能级结构的基础上,通过Tm³⁺的掺杂引入了更深的陷阱TB,并增加原有陷阱TA浓度,进而优化了材料的光存储容量及光激励特性。对比研究了系列样品的初始光激励发光强度和热释光强度随着Tm³⁺掺杂量的变化规律,证实陷阱TB为光激励发光提供了有效俘获中心。当Tm³⁺的掺杂摩尔分数x=0.03时,材料中的陷阱TB的浓度达到最高值,同时光激励发光强度最大。对比Tm³⁺共掺前后热释光图谱,通过Chen's半宽法计算出了引入陷阱TB的陷阱深度。实验结果证实材料中TB的浓度对其光激励发光性能起着决定性的作用。在980 nm激发下,由深陷阱TB释放出来的电子可以再次被浅陷阱TA俘获,这种浅陷阱TA的再俘获效应在光激励发光过程中表现为光激励余辉现象。}     

Nucleation of domains under the influence of temperature in Ba5Ti2O7Cl4

It is found that the nucleation of domains can take place in Ba₅Ti₂O₇Cl₄ under the influence of temperature unlike in many other ferroelectrics. The nucleated domain can also be removed from the structure under the randomizing effect of temperature. These observations have been explained on the basis of a nucleation model of Ingle and coworkers suggested for KNbO₃. Similarity of physical situation in KNbO₃ and Ba₅Ti₂O₇Cl₄ regarding the existence of ordered point defects inducing nucleation of domains around them has been highlighted. This surprising similarity is suggested to be due to the physical processes occurring at the phase transition rather than due to any structural resemblance. The nature of nucleation occurring under the influence of temperature is shown to be identical with the nature of nucleation occurring under the influence of externally applied stress, and/or DC electric field. A new technique of identifying point defects responsible for nucleation of domains is reported.     

爆轰和燃烧法合成SrAl2O4：Eu2+，Dy3+纳米发光粉

 在低温条件下分别用爆轰法和燃烧法制备出了SrAl₂O₄：Eu²⁺,Dy³⁺ 纳米发光粉。从合成条件、热处理温度等方面详细对比了爆轰法和燃烧法对所制备的SrAl₂O₄：Eu²⁺,Dy³⁺纳米发光粉的晶体生长行为、粒子形貌和光学性质等的影响。研究表明,随着热处理温度的升高,爆轰法制备的纳米发光粉的平均粒径逐渐增大,而燃烧法制备的纳米发光粉的平均粒径先减小后增大,在600 ℃时平均粒径存在一个极小值。在同样热处理温度下,爆轰法制备的纳米发光粉的平均粒径增长明显高于燃烧法合成的纳米发光粉的平均粒径。最后讨论了长余辉的发光机理,并给出了如何改进合成方法的建议。     

The influence of some processing conditions on host crystal structure and phosphorescence properties of SrAl2O4:Eu2+, Dy3+ nanoparticle pigments synthesized by combustion technique

The spectroscopic and host phase properties of SrAl₂O₄:Eu²⁺, Dy³⁺ phosphors with a series of different initiating combustion temperature, urea concentration as a fuel and critical pH of precursor solution are investigated. The SrAl₂O₄:Eu²⁺, Dy³⁺ nanoparticle pigments were obtained by exothermic combustion process within less than 5 min. The sample that ignited at initiating combustion temperature of 600 °C exhibits highest intensity emission peak at 517 nm in which the SrAl₂O₄ host phase has the maximum fraction of monoclinic SrAl₂O₄ phase. The excitation spectra consist of 240 and 254 nm broad peaks. The experimental results show that the optimum ratio of urea is 2.5 times higher than theoretical quantities for best emission condition of SrAl₂O₄:Eu²⁺, Dy³⁺ phosphor particles. The critical pH was obtained about 5.2. The crystallite size of these pigments is about 40 nm before thermal treatment and 62 nm after thermal treatment, respectively.     

A reaction cell for time‐resolved in situ XAS studies during wet chemical synthesis: the Cu2(OH)3Cl case

The use of in situ time‐resolved dispersive X‐ray absorption spectroscopy (DXAS) to monitor the formation of Cu₂(OH)₃Cl particles in an aqueous solution is reported. The measurements were performed using a dedicated reaction cell, which enabled the evolution of the Cu K‐edge X‐ray absorption near‐edge spectroscopy to be followed during mild chemical synthesis. The formed Cu₂(OH)₃Cl particles were also characterized by synchrotron‐radiation‐excited X‐ray photoelectron spectroscopy, X‐ray diffraction and scanning electron microscopy. The influence of polyvinylpyrrolidone (PVP) on the electronic and structural properties of the formed particles was investigated. The results indicate clearly the formation of Cu₂(OH)₃Cl, with or without the use of PVP, which presents very similar crystalline structures in the long‐range order. However, depending on the reaction, dramatic differences were observed by in situ DXAS in the vicinities of the Cu atoms.