Eu3+掺杂的铌酸钠钾陶瓷的制备及性能研究

采用固相烧结法制备了Eu³⁺掺杂的铌酸钠钾（KNN）陶瓷。用X射线粉末衍射仪、荧光光谱测试仪和LCR精确阻抗测试仪等对其结构、发光性能和介电性能进行表征。XRD结果显示样品为钙钛矿结构。荧光分析结果表明,致密度对KNN陶瓷材料发光性能有一定的影响,Eu³⁺掺杂量是影响其发光性能的重要因素。其中掺杂Eu摩尔分数为4%的样品在930℃焙烧后其发光最强,在396 nm紫外光激发下,发射光谱最强峰在614 nm,对应于Eu³⁺的⁵D₀-⁷F₂电偶极跃迁。样品经3 kV/cm、110℃极化30 min后进行压电性能检测,结果表明提高Eu³⁺掺杂量以及陶瓷的致密度,可改善压电性能。其中掺杂4%Eu的KNN压电常数D₃₃最大为98 pC/N,在1 kHz、100℃时,介电常数最小为217,介电损耗tanθ=0.199,且仍然保持较高的居里温度T_c=426℃。     

Er3+/Yb3+共掺的氧化镧钇透明陶瓷的光谱性能研究

采用传统无压烧结工艺制备了Yb³⁺/Er³⁺共掺的氧化镧钇透明陶瓷并对其光谱性能进行了研究.样品具有较大的吸收和发射截面.La₂O₃的添加使样品的荧光寿命(τ_s)与玻璃接近，当Yb³⁺和Er³⁺的掺杂量分别为5at%和0.5at%时，测得τ_s=9.65　ms.这种荧光寿命长、发射截面大和线宽窄的特性有利于微型、可集成化和大功率激光输出的实现. 关键词： 透明陶瓷 吸收光谱 发射光谱 荧光寿命     

Y2Ti2O7:Tm3+的制备及其发光性能研究

采用溶胶-凝胶法(Sol-gel)制备了不同烧结温度和Tm³⁺掺杂浓度的Y₂Ti₂O₇:xTm (x=0.005,0.01,0.03,0.05)荧光粉,分别采用X射线衍射分析仪(XRD)、透射电子显微镜(TEM)和荧光光谱仪对样品的晶型结构、形貌以及发光性能进行了表征。XRD结果表明,所得到的样品为单一立方相烧绿石结构。样品在361 nm紫外光激发下发射出 蓝光,其峰值波长为456 nm,对应于Tm³⁺的¹D₂→³F₄跃迁。1 000 ℃烧结的Y₂Ti₂O₇: 0.01Tm³⁺样品具有较好的发光性能。样品在456 nm处的相对发光强度随Tm³⁺掺杂浓度的增大先升高后降低,在Tm³⁺摩尔分数为1%时达到最大,即出现了浓度猝灭现象。     

Na0.25K0.25Bi0.5TiO3无铅压电陶瓷的介电特性研究

用固相反应法制备了Na_0.25K_0.25Bi_0.5TiO₃ (NKBT50)陶瓷，研究了该陶瓷在室温至400℃温度范围内的介电性能.发现该陶瓷的介电温谱与烧结气氛、极化状态有关.在空气中烧结的未极化样品在70℃附近存在介电和损耗峰，而极化后及在氧气氛中烧结的样品并不存在该介电、损耗峰.分析认为70℃的介电和损耗峰与氧空位形成的缺陷偶极子的极化弛豫有关.热激电流显示，陶瓷的去极化温度为225℃，与此相对应的介电、损耗峰也 关键词： 介电性能 氧空位 极化弛豫 钛酸铋钠钾     

Cr3+:Al2O3透明多晶陶瓷光谱特性分析

对透光性良好的Cr³⁺:Al₂O₃透明多晶陶瓷的光谱性能 进行了研究，其吸收光谱中吸收峰与单晶红宝石相一致，按吸收光谱和Tanabe-Sugano能级 图，算出其晶场强度参数D_q及Racah参数B分别为1792cm^-1， 689cm ^-1，D_q/B=2.6，陶瓷中Cr³⁺离子所处格位的晶体场强 比单晶弱一些，但Cr³⁺:Al₂O₃透明陶瓷仍属于强场晶 体材料；当Cr³⁺掺杂浓度到达0.8wt%时，陶瓷的发射谱仍保持较好的R线发射 ；随Cr³⁺掺杂浓度的增大，激发峰位发生“红移”.在Cr³⁺:Al₂O₃透明多晶陶瓷的荧光谱上，发现一个波长为670nm的发射峰，经激发 谱确认为Cr³⁺的发射峰. 关键词： 氧化铝 透明陶瓷 离子格位 光谱性质     

(Na1/2Bi1/2)Cu3Ti4O12陶瓷的微观结构和电学性质

利用固相反应法在不同烧结温度条件下制备了一系列(Na_1/2Bi_1/2)Cu₃Ti₄O₁₂(NBCTO)陶瓷样品,研究了它们的晶体结构、微观组织结构、介电性质和复阻抗及其随温度的变化. 实验发现NBCTO陶瓷所呈现出的电学性质与CaCu₃Ti₄O₁₂陶瓷相应的电学性质非常类似. 烧结温度为990℃至1060℃范围的NBCTO陶瓷样品室 关键词： 高介电材料 介电性质 复阻抗 内阻挡层电容     

Dy掺杂对Sr2Bi4Ti5O18铁电陶瓷性能的影响

用传统固相烧结法制备了Sr₂Bi_4-xDy_xTi₅ O₁₈(SBDT-x, x=0—0.20)陶瓷样品. x射线衍射分析表明, 微量的Dy掺杂没有影 响Sr₂Bi₄Ti₅O₁₈(SBTi) 原有的层状钙钛 矿结构. 通过研究样品的介电特性, 发现Dy掺杂减小了材料的损耗因子, 降低了样品铁电- 顺电相转变的居里温度. 铁电性能测量结果表明, 随Dy含量的增加, SBDT-x系列样品的剩余 极化先增大, 后减小. 当Dy掺杂量为0.01时, 剩余极化达到最大值, 约为20.1 μC·cm^-2. 掺杂引起剩余极化的变化, 与材料中缺陷浓度、内应力以及晶格畸变程度等因 素有关, 是多种作用机理相互竞争的结果. (Bi₂O₂)²⁺ 层通常被看作是绝缘层和空间电荷库, 对材料的铁电性能起关键作用. 掺杂离子进入(Bi2O₂)²⁺层会导致铁电性能变差. 关键词： 2Bi₄Ti₅O₁₈陶瓷')" href="#">Sr₂Bi₄Ti₅O₁₈陶瓷 Dy掺 杂 铁电性能 居里温度     

不同价态稀土元素Yb掺杂ZnO的电子结构和光学性质

基于密度泛函理论, 采用第一性原理平面波超软赝势法, 对六方纤锌矿结构的ZnO晶体和Yb²⁺, Yb³⁺分别掺杂ZnO晶体进行几何优化, 并在此基础上计算得到了未掺杂ZnO晶体及不同价态Yb元素掺杂ZnO体系的空间结构、 能带、电子态密度及光学性质.结果表明: 掺杂后体系形成能减少, 稳定性增加, 并引入了Yb-4f杂质能级. 掺杂不同价态的Yb元素对能带结构产生了不同的影响, 并且都使体系的光学性质发生了明显变化.与纯ZnO相比, Yb²⁺, Yb³⁺ 分别掺杂ZnO体系的介电函数虚部在0.46 eV处均出现新峰, 静态介电函数明显增大, 吸收带边均红移, 并在0.91 eV处出现较强吸收峰, 对产生这一现象的原因给出了定性的讨论. 关键词： 掺杂 ZnO 不同价态 第一性原理     

钨酸铅晶体中的偶极缺陷

在用阻抗谱研究PbWO₄（PWO）晶体的介电特性时发现，掺La³⁺的PW O晶体中存在典型的介电弛豫现象，它被归因于La³⁺进入Pb位并与铅空位V_Pb缔合 成偶极缺陷.这一结果不仅清楚地证明了PWO晶体中铅空位的存在，而且表明阻抗谱测试可以成为PWO晶体微结构研究的有力工具.以阻抗谱测试为主要工具，结合光吸收谱（包括红外谱）和x射线光电子能谱，阐明了在异价掺杂离子（3+，4+，5+以及3+和5+双掺）掺杂的PWO晶体中 关键词： 钨酸铅 偶极缺陷 异价掺杂 退火效应     

稀土掺杂Gd2Te4O11亚碲酸盐荧光粉的合成及其发光性能

采用水热法制备了一系列稀土Dy³⁺,Tb³⁺,Eu³⁺掺杂的极性Gd₂Te₄O₁₁(GTO)亚碲酸盐荧光粉.对样品的物相结构、形貌和热稳定性等进行了表征,测试了样品的发光性能.结果显示,所制样品均为单相,呈短杆状形貌,尺寸在微米量级,热稳定性能良好.对于GTO:Dy³⁺荧光粉,在紫外光激发下的发光主要位于黄绿光区,获得最强发光强度的掺杂浓度为2.5%,色坐标为(0.39,0.43);荧光衰减曲线表明GTO:Dy³⁺样品发光寿命随着掺杂浓度增大逐渐减小,与Dy³⁺离子间的交叉弛豫有关.对于GTO:Eu³⁺荧光粉,在紫外光激发下的发光主要位于红光和橙红光区,其发射强度随着Eu³⁺掺杂浓度的增大而增强.当掺杂浓度为10%时,样品发光的色坐标为(0.62,0.38),位于橙红光区,且样品的发光寿命几乎不受掺杂浓度影响.对于GTO:Tb³⁺     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Polymer gratings based on photopolymerization for low-order distributed feedback polymer lasers

Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.