化学气相沉积法生长透明硒化锌多晶

采用化学气相沉积(CVD)法,在Zn-Se-Hz-Ar体系中生长了用于红外光学窗口的ZnSe透明多晶体。测定了ZnSe样品的XRD谱和红外透过光谱,用光学显微镜观察了样品的显微形貌;讨论了CVD工艺中生长参数对ZnSe晶体质量的影响。研究结果表明：通过优化的生长工艺,生长温度在500～750℃,压力在100～1500Pa的范围内,可以制备出高质量ZnSe多晶体;在8～12μm波段范围内,其红外透过率达70％以上。     

Ho~(3+)掺杂Bi_4Si_3O_(12)晶体的生长与光谱特性

采用坩埚下降法生长了尺寸为f25 mm×100 mm的Ho~(3+)掺杂的Bi_4Si_3O_(12)(BSO:Ho)晶体,研究了所得晶体的透射光谱、激发光谱、发射光谱等特性。结果表明:BSO:Ho晶体透射光谱与纯BSO晶体基本一致,在350~800 nm波长范围的透过率约为80%,吸收边在286 nm处;在360、454和537 nm处存在与Ho~(3+)有关的吸收峰;激发光谱在240~310 nm波段出现1个宽的激发带,峰值在290 nm左右;发射光谱中除480 nm发射带外,在573 nm附近有多个与Ho~(3+)有关的尖锐发射峰。BSO:Ho晶体的主要发光分量的荧光衰减时间为94.41 ns,表明掺杂0.1%Ho~(3+)(摩尔分数)有利于提高BSO晶体的闪烁性能。     

Mo:Sb:PbWO_4闪烁晶体的生长与发光性能

采用坩埚下降法生长了Mo:Sb:PbWO4(Mo:Sb:PWO)晶体.通过透射光谱、X射线激发的发射谱、光产额和荧光寿命的测试,研究了Mo,Sb双掺杂对PbWO4晶体的光谱和闪烁性能的影响.结果表明:与未掺杂晶体相比,掺杂样品提高了PWO晶体在350～430 nm波段的透过率,消除了350nm吸收,吸收边变得陡峭并且向长波方向偏移.Mo:Sb:PWO晶体的发光谱存在400～650nm的宽带,发光主峰为510hm,发光强度得到提高.尺寸为10mm×10mm×20mm的Mo:Sb:PWO晶体样品,在1000ns的积分时间门宽内光产额最大值可达70photon-electrons/MeV,约为BhGe3O12(BGO)光产额的7.2%.光产额的提高主要来自于Mo:Sb:PbWO4晶体发光中的慢发光成分的增加.     

新型衬底材料γ-LiAlO2热稳定性研究

研究了温度梯度法生长的γ-LiAlO2晶体在1100℃不同气氛处理的热稳定性。借助扫描电子显微镜和X射线衍射分析发现：1100℃／10h真空和空气处理后的样品表面分别形成了均匀微孔状和岛状LiAl5O8多晶;而富Li气氛处理后样品表面仍然光滑且仍为LiAlO2。用Leitz大视场显微镜观察重新抛光后样品内部宏观缺陷,发现空气和真空处理后样品缺陷增多,分别为岛状和条纹状缺陷;而富Li气氛处理后样品中缺陷明显减少。对比不同气氛处理的4块样品吸收光谱,确认了真空和空气处理产生的196nm吸收峰可能是Li空位吸收峰。     

中子辐照6H-SiC晶体的光学性质及缺陷分析

利用透射电子显微镜、紫外--可见--近红外光谱和Raman光谱,对剂量为1.67×1020 n/cm2中子辐照的n型半导体6H-SiC晶体进行了微观结构、光学性质及退火过程的研究。结果显示,辐照并没有造成样品的完全非晶化,辐照缺陷主要是点缺陷及其聚集体。辐照后的样品的光吸收明显增加,带隙变小,Urbach能量变大,且在1 178、1 410和1 710nm处出现新的吸收峰。1 178和1 410nm峰的出现归因于辐照产生的Si空位VSi。对辐照样品进行了室温至1600℃退火,发现800℃是退火过程的转折点。低于800℃退火时,样品中的Frankel对、间隙原子和C空位VC消失;高于800℃退火时,含Si空位VSi缔合缺陷及复杂缺陷团分解湮灭。为了解释与VSi有关的多个光谱峰,建立了SiC中硅空位的"类铍原子模型"。     

大尺寸氟化钙单晶的光谱特性

采用坩埚下降法成功生长了φ100 mm CaF2晶体,研究了不同条件生长单晶的缺陷和光谱性能.结果表明:当晶体生长过程中引入水等含氧杂质时,所生长的晶体不仅在1 500 nm附近产生非常宽的OH-两倍振动吸收带,而且在可见-紫外波段也形成强烈的色心吸收带.同时,杂质离子Ce3 的存在也导致晶体出现306 nm的吸收带.     

KDP和ADP晶体的生长以及紫外透过性能研究

作为非线性光学晶体材料,由于晶胞参数的不同,KDP、ADP在生长方面以及性质上都存在着差异。本文采用"点籽晶"快速生长法对KDP和ADP晶体的生长进行了研究。同时测量了快速生长法生长的KDP和ADP晶体在紫外波段的透射光谱性能,实验证明ADP晶体的紫外透过率要优于KDP晶体。     

真空烧结非计量La1–xErZr2O7–3x/2透明陶瓷

制备光学性能优异的陶瓷材料是无机材料研究和发展的重要方向。近年来,结构与功能一体化的透明陶瓷已然是材料研究的热点。非计量La_1–xErZr₂O_7–3x/2透明陶瓷采用燃烧法和真空烧结技术成功制备,通过X射线衍射仪、Raman光谱仪、扫描电子显微镜等测试技术,研究了La含量对相组成、微观结构和光学性能的影响。结果表明,随着La含量的降低,样品中烧绿石相和缺陷萤石相的共存状态逐渐转变为缺陷萤石相。x=0.1的样品在红外区域2.5～7.0μm表现出稳定的透过率,其透过率约为74.8%(厚度1 mm),最大红外截止值在8.5～9.0μm。x=0.2的样品在可见光到中红外区域表现出出色的透过率,并且在980 nm波长激发下,该陶瓷在684 nm处呈现出强烈的红光发射,在561 nm处呈现出微弱的绿光发射,在446 nm处呈现出微弱的蓝光发射。此外,La_1–xErZr₂O_7–3x/2透明陶瓷的透过率光谱中出现大量吸收峰,La的适量降低有助于提高光学质量。与化学计量La...     

宽波段近红外吸收涂层的制备及性能研究

以近红外(NIR)吸收染料为光吸收剂,羟基丙烯酸酯为预聚物树脂,光学级聚酯(PET)薄膜为基材,采用湿法涂布的方式制备了宽波段近红外吸收涂层材料。通过透光率测定,TG-DSC和光学显微镜分析研究了涂层的光学性能以及耐热稳定性和耐紫外光老化性能。结果表明,当N660,N720,N800和N890的质量分数分别为0.4%,0.6%、0.8%和1.0%时,所制备的涂层具有良好的宽波段近红外吸收性能和较高的可见光透过率,其在660~930 nm宽波段的平均透光率低于0.2%,同时在380~600 nm可见光波段的平均透过率超过45%。此外,涂层具有较好的耐热稳定性,其热分解温度为257.8℃。添加质量分数0.2%的抗紫外老化剂后,涂层的耐紫外光辐照老化性能显著提高。     

提拉法生长钽酸钾晶体

用提拉法生长出了一系列钽酸钾(KTaO3)晶体,其中最大可达31 mm×31 mm×40 mm,质量为247g.X射线粉末衍射仪测试结果表明:KTaO3单晶具有立方结构,晶胞参数a=0.398 88 nm.透射光谱显示:KTaO3单晶在340～3 500 nm的波长范围内有宽广的透光波段,仅在2 875 nm的处有吸收峰.讨论了KTaO3晶体的表面形貌、宏观缺陷及生长习性.     

LBO晶体的生长缺陷研究

采用化学腐蚀光学显微法和同步辐射截面形貌术研究了三硼酸锂（ＬＢＯ）晶体的生长缺陷,实验结果表明,ＬＢＯ晶体中的主要缺陷是位错、包裹物和形界,讨论辽些缺陷形成的原因和降低缺陷的措施。     

Selective O–H Bond Cleavage in the Radiolysis of Quartz

Cleavage of the O–H bond in quartz was studied by Fourier transform infrared spectroscopy and ESR spectroscopy. When quartz single crystals and fused silica glass are γ-irradiated at 77 K, hydrogen atoms are produced by rupture of O–H bonds. The initial efficiency of O–H bond cleavage in quartz single crystals, i.e. the initial yield of H atoms, was three times as great as that in fused silica glass, although the concentration of O–H bonds in quartz single crystals (70 ppm) is much lower than that in fused silica glass (4000 ppm). The efficiency of O–H bond cleavage in quartz single crystals indicates that energy transfer from the irradiated single crystal to the O–H bonds takes place effectively at 77 K. The efficiency of O–H bond cleavage decreases with increasing γ-ray dose, i.e. with increasing amounts of radiation-induced defects in quartz single crystals. When the radiation-induced defects are removed by annealing the irradiated quartz single crystal at 773 K, the O–H bonds are ruptured again as effectively as for a fresh quartz single crystal. The distance of the energy transfer, estimated by a target model, is ∼15 nm.     

锗酸铋晶体缺陷和小面生长

对坩埚下降法生长锗酸铋闪烁晶体的缺陷进行了研究，除使用通常研究透明晶体的光学方法，由于ＢＧＯ晶体在受到光辐照损伤对短波长光具有高的吸收系数，因此还采用近紫外光吸收形貌法研究晶体缺陷，以及缺陷与晶体小面之间的关系，并根据ＢＧＯ晶体的结晶习性和小面形成机理提出了减少和消除晶小面生长及缺陷的方法。     

低吸收PWO晶体生长需解决的问题

系统地研究了生长晶体概况，重点为掺杂离子、生长工艺和设备改进对PbWO4晶体性能的影响。     

6H-SiC单晶的生长与缺陷

采用升华法,在一定的温度、气体压力和流量的条件下,生长了尺寸ф50．8mm的6H—SiC单晶。利用光学显微术观察了原生晶体的表面形貌,发现了微管在晶体表面的露头点具有明显的多个螺位错成核特征。采用透射模式对抛光晶片进行观察,发现了SiC晶体内的典型缺陷,如：负晶、微管、碳颗粒等,并对它们的形成机理进行了讨论。     

Investigating the Mechanical Properties of RDX Crystals Using Nano‐Indentation

The shock sensitivity of RDX is of major interest for the development of insensitive munitions. Previous research has implied that internal defects that form within RDX crystals have a strong sensitising effect, increasing the probability of shock initiation. During the NATO Reduced sensitivity RDX Round Robin (R⁴) program the number of internal defects within RDX crystals of differing qualities were assessed by optical microscopy and a scoring system. The results suggested that RDX crystals with many internal defects were more sensitive. Studies investigating the mechanical properties of bulk RDX have shown that lots consisting of poorer crystals are weaker. This study investigates the mechanical properties of individual crystals from different RDX lots using nano‐indentation. It is shown that crystals with many internal defects have reduced modulus of elasticity, stiffness and prone to greater deformation under applied load. The results also show a correlation between these parameters and previously reported shock sensitivity data.     

Evaporation-Assisted Formation of Three-Dimensional Photonic Crystals

The process of evaporation-assisted formation of three-dimensional photonic crystals was studied. The photonic crystals were fabricated by stacking uniform-sized silica spheres into regularly arranged structure with solvent evaporation and sedimentation. Effects of important process parameters, including type of solvent (water and ethanol), system temperature (40° and 60°C), and material for sedimentation cell (quartz, polymethyl methacrylate, and Teflon), on structure regularity of the resulting photonic crystal were investigated. The structure regularity was evaluated with scanning electron microscope graphs and stop band depth achieved in optical absorption spectra. As revealed from the experimental results, photonic crystals of better quality were obtained by using suspending solvents of higher surface tension (water), lower system temperatures (40°C), and sedimentation cell materials of higher critical surface tension of wetting (quartz).     

石英晶体微天平法测定聚丙交酯中氮气溶解度

采用石英晶体微天平方法(QCM),测定了在不同温度和压力条件下,氮气在聚丙交酯(PLA)中的溶解度。试验中,QCM由测定和参考两个AT切向的石英晶片组成,其中作为参考的石英晶片用来反映压力增加和气体粘度对石英晶片的影响。由氮气在聚苯乙烯中溶解度的试验结果与文献数据比较,证实了该方法的可靠性。试验测定了在295.82 K,305.25 K和314.83 K时,不同压力下,氮气在PLA中的溶解度。结果表明,氮气在PLA中的溶解度随温度和压力的增加而增加,其随温度变化的趋势与其它临界温度较低的气体在聚合物中溶解度的变化规律一致。     

Nucleation and growth of graphene/Mo2C heterostructures on Cu through CVD

We investigated the chemical vapor deposition synthesis of Mo₂C/graphene heterostructures on a partially wetted liquid copper surface, studied the morphology of resulting phases using electron and optical microscopy, and determined the rate-limiting step for the growth of Mo₂C on graphene. The morphology of the Mo₂C crystals varied from the center to the edge of the copper substrate because of the change in the Mo diffusion pathways owing to the variation in the thickness of the Cu substrate. Thin, hexagonal-shaped crystals of Mo₂C were found in the central region, where Cu is the thickest. In addition, the growth pressure substantially affects the nucleation and growth kinetics of both Mo₂C and graphene. At high pressures (750 Torr), the graphene layer fully covered the Cu surface and Mo₂C crystals formed with a regular shape, while at low pressures (5 Torr), the nucleation of both domains was suppressed, leading to the evolution of Mo₂C crystals with irregular shapes. The activation energy for the growth of Mo₂C on graphene was calculated to be 3.76 ± 0.3 eV, and the diffusion of Mo to the Cu surface through uncovered Cu or graphene vacancies/defects was determined to be the rate-limiting step.     

Structure and Electronic States of Defects in Spinel of Different Compositions MgO·nAl2O3:Me

This paper reviews the nature of defects and optical centers in magnesium aluminate spinel. The identification of absorption and luminescence bands was used to investigate the influence of UV and electron irradiation on optical center formation. Crystals examined were nominally pure MgO- n Al₂O₃ crystals with compositions in the series n = 1.0, 1.5, 2.0, and 2.5. MgO·Al₂O₃ crystals doped with transition-metal ion dopants were also studied to determine the influence of impurities on the nature and concentration of lattice defects in spinel. Results strongly suggest that absorption bands at 3.78 and 4.15 eV, and luminescence bands near 5 eV, may be attributed to optical centers on antisite defects. It is also apparent that through the introduction of specific amounts of Mn and Cr ions, the concentration of optical centers (which are related to defects such as cation antisites in the spinel structure) can be considerably changed.