PMN-PT:Er3+铁电晶体的光谱特性与J-O理论分析

为了探索Er3+在Pb(Mg1/3Nb2/3)-PbTiO3弛豫铁电晶体场中的发光特性,采用高温溶液法生长了PMN-32PT:Er3+弛豫铁电单晶,测试并分析了该晶体的微观形貌、相结构、吸收光谱与上转换发射光谱,利用Judd-Ofelt理论计算了Er3+在PMN-32PT晶体场中的J-O振子强度参数.该晶体四方相晶胞参数为a=0.4023 nm,c=0.4033 nm,V=0.06523 nm3,单斜相晶胞参数为a=0.4035 nm,b=0.4032 nm,c=0.4031 nm,V=0.06557 nm3.振子强度参数Ω2=1.77×10-20 cm2,Ω4=1.50×10-20 cm2,Ω6=0.79×10-20 cm2,δrms=0.18×10-6;4 I11/2的理论能级寿命τ=1.75 ms.样品晶体在980 nm光源激发下,发射出了很强的绿光(552 nm).研究结果表明PMN-PT:Er3+单晶是一种性能优异的新型发光晶体.     

CdLa2(WO4)4晶体的生长及发光性能的研究

以高温固相法成功合成了CdLa2(WO4)4多晶料,采用垂直坩埚下降法进行了晶体的生长.CdLa2(WO4)4晶体属于四方晶系白钨矿结构,其晶胞参数为:a=b=5.209 ?,c=11.325 ?,晶胞的体积为307.26 ?3,其密度为7. 494 g/cm3.在室温下测量了晶体的光致发光光谱、X射线激发发射光谱、光致发射衰减时间等.结果表明:在296 nm紫外光的激发下,样品在350~600 nm范围内具有宽阔的蓝绿发光带,发射峰的峰值为470 nm.并且其光致发射衰减时间为3.4 ns,在X射线激发下也有良好的发光性能.     

RbY2Cl7:Ce晶体的生长和闪烁性能研究

采用坩埚下降法,在真空密封的石英坩埚中成功生长出复合稀土卤化物RbY2Cl7:Ce单晶.此晶体属于正交晶系,晶胞参数为:a=1.27469 nm,b=0.69302 nm,c=1.26655 nm.熔点为617℃.表征了该晶体的X射线光致激发-发光光谱、激发发射光谱、γ射线多道能谱及激发衰减曲线等闪烁性能.RbY2Cl7:Ce的激发-发射光谱显示发射峰在389 nm左右,激发峰在336 nm左右.在137Cs源的γ射线激发下能量分辨率约为9.8;,闪烁衰减时间约为35 ns.     

新型N-杂环卡宾咪唑盐的合成、表征与抑菌活性研究

以喹哪啶作为桥联基团,合成了五个新型N-杂环卡宾咪唑六氟磷酸盐化合物(5a～5e),其结构经1H NMR,13CNMR表征,用X-ray单晶衍射确定5b、5c和5e的晶体结构.单晶结构分析表明,晶体5b和5c均为三斜晶系、P1空间群;5e晶体为单斜晶系、Cc空间群.5b的晶胞参数:a=6.945 1(10)nm,b=12.0166(18) nm,c=14.791(2) nm,α=91.997(11)°,β=95.340(12)°,γ=105.845(8)°;5c的晶胞参数:a=9.975(3) nm,b=11.056(4) nm,c =12.382(4)nm,α=99.010(4)°,β=103.527(3)°,γ=112.734(3)°;5e的晶胞参数:a=18.058 9(18) nm,b=12.510 0(9) nm,c=13.365 9(12) nm,α=90.00°,β=124.522(7)°,γ=90.00°.抑菌实验结果表明,5a～5e对金黄色葡萄球菌和大肠杆菌有一定的抑制作用.     

NaCo2O4晶体的生长,形貌和生长机理研究（英文）

采用自发成核方法,以NaCl-Na2CO3为助熔剂,生长了毫米级的NaCo2O4晶体。通过X射线衍射对晶体作了表征。利用扫描电子显微镜和原子力显微镜研究了晶体的形貌和生长机理。结果表明:所得晶体是NaCo2O4,属于六方晶系,晶胞参数:a=b=0.2842 nm,c=1.0894 nm,V=0.0761997 nm3。NaCo2O4晶体是沿c轴层状生长的,同时从阴离子配位多面体的角度分析了晶体的形貌。     

一种新络合盐晶体——K3[InCl6]的合成

在采用本实验室提出的络盐法制备氧化铟锡(Indium-tin-oxide,简称ITO)纳米粉末的试验过程中发现和制备了一种新络合盐晶体--K3[InCl6].通过XRD、SEM和CCD等测试手段对其物相、形貌、元素成份和结构进行了表征.结果表明:该晶体属单斜晶系,空间群为P21/c,分子式为K3[InCl6],Z=4,其晶胞参数为:a=1.2188nm,b=0.7553nm,c=1.2703nm,α=90.00°,β=108.96°,γ= 90.00°,V=110.598nm3.     

羟基蛋氨酸铜螯合物的制备与表征

以羟基蛋氨酸和铜盐为主要原料,合成了两种羟基蛋氨酸铜螯合物,通过元素分析、红外光谱、X射线粉末衍射和热重差热分析等对其进行了组成和结构表征.红外光谱确证铜离子与羟基蛋氨酸中的羧基氧原子、羟基氧原子及甲硫基硫原子配位.结果表明,两种配合物均属于单斜晶系,Cu(MHA)·0.5H2O的晶胞参数为:a=0.9035nm,b=1.1739 nm,c=1.5515 nm,β=95.69°;Cu(HMHA)2的晶胞参数为:a=0.9698 nm,b=1.8483 nm,c=1.6677nm,β=95.58°.两种配合物在200℃以上开始分解,残余物主要为CuS.     

钒酸镝晶体生长和磁光性能研究

采用液相沉淀法制备了钒酸镝(DyVO4)粉体,使用提拉法生长了DyVO4磁光晶体,通过XRD确定生长的DyVO4晶体没有杂相,晶体的晶胞参数是a =b =0.71434 nm,c =0.6313 nm,α=β=γ=90°,属于四方晶系.晶体经过定向切割加工成c轴晶向的片状和柱状样品.测试了DyVO4晶体样品的光学性能和磁光性能.结果 显示,样品在500～700 nm波长范围内,具有很高的透过率,在76;～ 79;之间,DyVO4晶体对应于532 nm、633 nm和980 nm的Verdet常数分别为-309 rad/m/T、-167 rad/m/T和-64 rad/m/T,性能优于商用磁光晶体TGG,有望在可见光波段实现应用.     

含铋双金属配合物的合成与表征

在水溶液中采用固液相反应法合成了二乙烯三胺五乙酸的含铋双金属配合物CaBi(dtpa)·5H2O(1)和MnBi(dtpa)·5H2O(2).用元素分析、X射线粉末衍射、红外光谱、原子吸收和热重分析等方法进行表征,确定了配合物的组成和结构,并对XRD数据进行了指标化.结果表明:两种配合物均为单斜晶系,CaBi(dtpa)·5H2O的晶胞参数为:a=1.2837 nm,b=0.8682 nm,c=1.3593 nm,β= 97.909 °;MnBi(dtpa)·5H2O的晶胞参数为:a=1.4359 nm,b=0.8666 nm,c=0.7369 nm,β =96.295 °.     

Ho3+掺杂Sc2SiO5激光晶体生长与光谱性能研究

采用提拉法分别生长了具有高光学质量的0.5at;和1.0at;的Ho∶ Sc2SiO5(Ho∶ SSO)激光晶体.研究表明晶体空间群为C2/c,晶胞参数为a=0.99723 nm,b=0.64261 nm,c=1.16843 nm,β=103.9°.Ho3+在SSO基质中的分凝系数为0.82.Ho∶ SSO晶体在2085nm处发射截面为1.12×10-20 cm2,发射光谱呈现一个1850～2150nm的宽发射带.当粒子数反转比率β=0.25时,增益截面σg即开始出现正增益.综合评估了晶体的激光性能,表明Ho∶SSO晶体是一种有潜力的2μm波段激光介质.     

Development of Pauling's concepts of geometric characteristics of atoms

The evolution of the geometric characteristics introduced by Pauling and their dependence on the specific features of the structure and chemical bonds have been considered. The values of the covalent and van der Waals radii are given as well as their relationships and mutual transitions.     

Relationship of Morphological Types of Dynamic Forms of Crystals

Crystallography Reports - The relationship of morphological spectra (sets of data on the morphological types of real polyhedral crystals and their probabilities under current physicochemical...     

A SAXS study of kinetics of aggregation of silica sols

SAXS in situ experiments on the evolution of TMOS solutions during hydrolysis and polycondensation lead to power laws with scaling exponents ≈ 2. It is suggested that this could be the result of the polydispersity of the samples and that only an apparent fractal dimension can be obtained in this way. Kinetic studies tend to indicate that agglomeration in the sol is the result of a diffusion-controlled process.     

Study of the possibility of interactive control of the surface profile of X-ray optical elements

We investigate the possibility of controlling the curvature parameters of parabolic mirrors that are modular elements of two types consisting of a base and thin inserts placed at the opposite side of the work surface. In the first type of modular elements, bending is controlled by the difference in the coefficients of the thermal expansion of the base and inserts. In the second type of elements, the profile is changed by the piezoelectric straining of the inserts under an electric field. A correlation is established between the parameters of modular elements and their surface curvature profile.     

A review of measurement of thermophysical properties of silicon melt

Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi₃ existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species.     

Mechanism of thermal expansion of structural modifications of zinc pyrovanadate

Crystal chemical characteristics of the α and β modifications of Zn₂V₂O₇ are calculated based on in situ high-temperature X-ray measurements. The expansion of the structure is found to be strongly anisotropic up to the negative volumetric thermal expansion of the α-Zn₂V₂O₇ unit cell in the temperature range of 300–600°С, α _V =–17.94 × 10^–6 1/K. The transformations of the “hard” and “soft” sublattices with an increase temperature and at the phase transition are considered in detail. It is shown that the negative volumetric thermal expansion of α-Zn₂V₂O₇ is due to the degeneracy of the zigzag-like shape of zinc–oxygen columns at constant distances between their vertices.     

Generation of crystal structures of heteromolecular compounds by the method of discrete modeling of packings

Within the method of discrete modeling of packings, an algorithm of generation of possible crystal structures of heteromolecular compounds containing two or three molecules in the primitive unit cell, one of which has an arbitrary shape and the other (two others) has a shape close to spherical, is proposed. On the basis of this algorithm, a software package for personal computers is developed. This package has been approved for a number of compounds, investigated previously by X-ray diffraction analysis. The results of generation of structures of five compounds—four organic salts (with one or two spherical anions) and one solvate—are represented.     

Investigation of the Mechanism of Influence of Stress Corrosion on the Development of Macroplastic Instabilities of Aluminum–Magnesium Alloy

Crystallography Reports - Macroscopic jumps of plastic deformation (few percent in amplitude) on creep curves of aluminum–magnesium alloy, caused by a local effect of concentrated solution of...     

Dependence of the parameters of equations of viscous flow on chemical composition of silicate melts

The temperature dependence of viscosity of silicate melts is discussed in the framework of the Avramov–Milchev (AM) equation. The composition is described by means of two parameters: the molar fraction, x, and the “lubricant fraction”, l. The molar fraction is the sum of the molar parts x_i of all oxides dissolved in SiO₂, the molar fraction of the latter being 1 ? x. It is shown that, with sufficient precision, two of the parameters of the AM equation can be presented as unique functions of the molar fraction. On the other hand, x is not sufficient to determine properly the reference temperature T_r , at which viscosity is η_r = 10¹³ [dPa.s]. Therefore, additional parameter, “lubricant fraction” l, is introduced. For each of the components, l_i is a product of molar part x_i and a specific dimensionless coefficient 0 ≤ k_i ≤ 1 accounting for the specific contribution of this component to the increased mobility of the system. It is demonstrated that, for l > 0, the reference temperature is related to the “lubricant fraction” l through the reference temperature T_r,SiO2 of pure SiO₂.     

Comparative analysis of two methods of calculation of the orientation of domain walls in ferroelastics

Two types of domain-wall equations are analyzed: the equations derived by the Sapriel method and the equations obtained by interface matching of the thermal-expansion tensor. It is shown that, for W-type domain walls, these methods yield the same equations. For W′-type domain walls, the equations obtained by different methods coincide for proper ferroelastics and differ for improper ferroelastics.