Sr1+xSm1-xAl1-xTixO4微波陶瓷介电性能研究

以SrCO3,Sm12 O3,Al2O3,TiO2为原料,采用固相反应法制备了Sr1+xSm1-xAl1-xTixO4(x=0,0.1,0.2,0.3)陶瓷,研究了SrTiO3掺人量对其显微结构和微波介电性能的影响.结果表明:SrSmAlO4晶相中固溶SrTiO3,晶胞出现了明显的膨胀;SrSmAlO4陶瓷中固溶SrTiO3相,可降低其烧结温度和陶瓷烧结体的密度;SrSmAlO4陶瓷中固溶SrTiO3相后,可提高其介电常数和品质因素,但对其温频系数影响较小.在1420C/2 h烧结条件下,Sr1.2Sm0.8Al08Ti0 2 O4陶瓷微波介电性能达到:εr=28,Q×f=52600 GHz,τf=4 ppm/℃.     

Conformational Studies of Substituted Chromans: Crystal Structures of 2,2′-(1E,1′E)-(2,3-Dimethylchroman-2,4-diyl)bis(Azan-1-yl-1-ylidene)bis(Methan-1-yl-1-ylidene)Diphenol (I) and 2,2′-(1E,1′E)-(2-Ethyl-3-Methylchroman-2,4-diyl)bis(Azan-1-yl-1-ylidene)bis(Methan-1-yl-1-ylidene)Diphenol (II)

Abstract  

The title compounds C₂₅H₂₄N₂O₃ (I) and C₂₆H₂₆N₂O₃ (II) crystallize in the triclinic space group P-1 with cell parameters a = 8.981(1), b = 9.933(1), c = 12.369(2) ?, α = 78.537(2), β = 84.515(2), γ = 73.561(2)° Z = 2 (I) and a = 11.4630(9), b = 12.955(1), c = 16.154(1) ?, α = 70.425(1), β = 87.403(1), γ = 71.850(1)°, Z = 4 (II). In both compounds the phenolic groups in the Schiff base substituents form intramolecular hydrogen bonds with the imine nitrogen atoms thereby rendering these substituents nearly planar. A detailed analysis of the amount by which the heterocyclic ring deviates from planarity (extent of puckering) in these and a series of related molecules shows that the extent of the deviation is largely unaffected by the number, size and placement of substituents on this ring.     

X-ray crystal structure of the 1:1 dimethylpicric acid–acenaphthene complex

The dimethylpicric acid–acenaphthene complex is orthorhombic, space group P2₁2₁2₁; at 24° a = 7.3685(1), b = 15.4159(1), c = 16.1296(3) Å, D _x = 1.491(2) g cm^–3, V = 1832.19(4) ų, Z = 4. The phenolic OH group in the dimethylpicric acid is intramolecularly hydrogen bonded to one of the ortho nitro groups with an OO distance of 2.500(2) Å. This nitro group is twisted out of the plane of the benzene ring by 8.2°; the twist angles of the other nitro groups are 52.6 and 83.5°. The acenaphthene molecule deviates slightly from planarity as a consequence of the torsion angle at CH ₂-CH ₂ being 1.8 rather then 0°. The molecules pack in stacks of alternating picric acid and acenaphthene molecules. Each stack is surrounded by a close-packed arrangement of six other stacks. The acenaphthene molecules are 2.7° away from being parallel to the benzene ring in the picric acid. The distances from the benzene ring to the acenaphthene carbon atoms range from 3.26 to 3.49 Å on one side of the ring and from 3.30 to 3.54 Å on the other.     

Structure of the 1∶1∶1 complex between 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6), 2,3-dichlorophenol,and water

The structure of the title compound, C₁₂H₂₄O₆·C₆H₄OCl₂·H₂O, has been determined by X-ray diffraction methods. The crystals are monoclinic, space groupP2₁ witha=8.628(2),b=13.767(4),c=9.676(2), =96.38(2)°, andD _x =1.295 Mg m^–3 forZ=2; 2355 reflections were recorded on a CAD4 diffractometer using CuK radiation atT=243° K. The structure was solved usingMultan andShelx. The finalR value based on 1901 reflections is 0.071. The 18-crown-6 molecule has approximatelyD _3d symmetry. The host molecule (18-crown-6), the guest molecule (dichlorophenol), and water form a super-molecule. Binding between host and guest is effected by bridging water molecule: the water and dichlorophenol molecule are linked by a very strong hydrogen bond (OO=2.58 Å); weaker interactions exist between water and oxygens of the crown ether (OO distances 2.85 and 2.90 Å).     

乙醇共沉淀法制备纳米Li[Ni1/3CO1/3Mn1/3]O2

采用乙醇共沉淀法制备纳米Li[ Ni1/3 Co1/3 Mn1/3] O2材料.采用XRD和SEM对合成材料进行了表征.结果表明:合成材料的粒径为纳米级,平均粒径可达60 nm,此种方法合成材料具有较好的层状结构和较低的阳离子混排程度.在2.8 ～4.3 V(vs Li/Li+)条件下进行充放电测试,结果表明材料具有较好的电化学性能,尤其在高倍率下(10 C),材料的放电性能可以达到大功率用电设备的要求.     

Miscibility gap calculation for Ga1−xInxNyAs1−y including strain effects

A method including strain effects is introduced for calculating the miscibility gap of the Ga_xIn_1−xN_yAs_1−y material system. The Gibbs free energy is computed using the delta lattice parameter model and the conventional solution model. The contribution caused by the strain energy due to the mismatch between substrate and epitaxial layer is added. The spinodal points can be calculated from this expression. The critical temperature above which the solid is metastable has been found to be increased due to strain effects. It is pointed out that the result of the calculation depends on the choice of substrate. The miscibility gaps for Ga_xIn_1−xAs, GaN_yAs_1−y and Ga_xIn_1−xN_yAs_1−y are evaluated by this method for a more realistic model of crystal growth.     

Ravil Vagizovich Galiulin (January 1, 1940–February 1, 2010)

Obituaries

Ravil Vagizovich Galiulin (January 1, 1940–February 1, 2010)     

Crystal and molecular structure of the H-bonded complex between 1-chloro-2-hydroxynaphthalene-3-carboxylic acid and dimethylformamide (1∶1)

Crystal structure determination of the title complex reveals that the dimethylformamide solvent is bound to the carboxylic function of the hydroxy acid, in the form of a 7-membered hydrogen-bonded loop involving both the expected O-HO and an apparently weak C-HO interaction between host and guest. There is a strong intramolecular hydrogen bond between the phenolic OH and the carbonyl oxygen. Close packing of the complex units is afforded by a herringbone type alignment of host molecules.     

Hg1-xMnxTe的化学抛光研究

本文根据窄禁带半导体Hg1-xMnxTe的物理、化学特性,采用不同浓度的Br2-MeOH作为抛光液对Hg1-xMnxTe进行化学抛光,发现用3;的Br2-MeOH腐蚀液时腐蚀速率平稳且容易控制,能有效去除表面划痕,得到光亮、整洁表面.AFM分析发现,化学抛光后表面粗糙度降低19.8;,整体均匀性提高.SEM分析发现,化学抛光后表面损伤层被全部去除.77 K时,化学抛光前后的范德堡霍尔测量发现,晶片化学抛光后,电阻率增加.     

形形色色的太阳电池（1）

最早问世的太阳电池是单晶硅太阳电池。硅是地球上极丰富的一种元素，几乎遍地都有硅的存在，可说是取之不尽。用硅来制造太阳电池，原料可谓不缺。但是提炼它却不容易，所以人们在生产单晶硅太阳电池的同时，又研究了多晶硅太阳电池和非晶硅太阳电池，至今商业规模生产的太阳电池，还没有跳出硅的系列。其实可供制造太阳电池的半导体材料很多，随着材料工业的发展，太阳电池的品种将越来越多。目前已进行研究和试制的太阳电池，除硅系列外，还有硫化镉、砷化镓、铜铟硒等许多类型的太阳电池。     

(Na1/2Bi1/2)TiO3-(Na1/2Bi1/2)(Zn1/3Nb2/3)O3无铅压电陶瓷的介电特性研究

采用固相合成法制备了(1-x)(Na1/2Bi1/2)TiO3-x(Na1/2Bi1/2)(Zn/23Nb2/3)O3(简写为(1-x)NBT-xNBZN)无铅压电陶瓷.研究了该体系陶瓷晶体结构、弥散相变特征与介电弛豫行为.X射线衍射分析表明,所研究的组成均能够形成纯钙钛矿(ABO3)型固溶体.当x≥0.5%摩尔分数时,该体系陶瓷具有三方、四方共存的晶体结构.材料的介电常数-温度曲线显示陶瓷具有两个介电反常峰Tf和Tm.修正的居里-外斯公式较好的描述了陶瓷弥散相变特征,弥散指数随x的增加而增加.x≤0.5%摩尔分数的陶瓷仅在低温介电反常峰Tf附近表现出明显的频率依赖性,随x的增加,陶瓷材料在室温和低温介电反常峰Tf之间都表现出明显的频率依赖性.根据有序-无序转变和宏畴.微畴转变理论探讨了该体系陶瓷介电弛豫特性的机理.     

Epitaxial lateral overgrowth of non-polar GaN(1 1̄ 0 0) on Si(1 1 2) patterned substrates by MOCVD

m-Plane GaN was grown selectively by metal–organic chemical vapor deposition (MOCVD) on patterned Si(1 1 2) substrates, where grooves aligned parallel to the Si〈1 1 0〉 direction were formed by anisotropic wet etching to expose the vertical Si{1 1 1} facets for growth initiation. The effect of growth conditions (substrate temperature, chamber pressure, and ammonia and trimethylgallium flow rates) on the growth habits of GaN was studied with the aim of achieving coalesced m-plane GaN films. The epitaxial relationship was found to be GaN(1 1? 0 0) || Si(1 1 2), GaN[0 0 0 1] || Si[1 1 –1], GaN[1? 1? 2 0] || Si[1 1? 0]. Among all growth parameters, the ammonia flow rate was revealed to be the critical factor determining the growth habits of GaN. The distribution of extended defects, such as stacking faults and dislocations, in the selectively grown GaN were studied by transmission electron microscopy in combination with spatially resolved cathodoluminescence and scanning electron microscopy. Basal-plane stacking faults were found in the nitrogen-wing regions of the laterally overgrown GaN, while gallium-wings were almost free of extended defects, except for the regions near the GaN/Si{1 1 1} vertical sidewall interface, where high dislocation density was observed.     

焙烧温度对Li[Mn1/3Ni1/3CO1/3]O2结构及电化学性能影响

采用碳酸盐共沉淀法制备了Li[Mn1/3Ni1/3Co1/3]O2,研究了前驱体的焙烧温度对材料结构和电化学性能的影响.XRD测试结果表明,800℃下焙烧得到的样品具有较好的层状结构和较低的阳离子混排程度.SEM测试表明合成材料具有球状形貌,平均粒径可达5μm,组成它的一次颗粒粒径平均为200nm.在2.8～4.3V(vs.Li/Li+)0.2C条件下进行充放电测试,800℃下合成的样品的首次放电比容量最高(159.06mAh·g-1),容量损失最小,循环50次后能保持初始放电比容量的95.7;.EIS分析结果表明,800℃焙烧的样品的电化学活性最好.     

Crystal structure of tris(triphenylsiloxy)borane·triphenylsilanol (1:1) adduct

The title compound crystallizes in the triclinic space group , with a = 14.458(6), b = 14.630(5), c = 14.721(8) Å, = 79.75(2), = 80.11(3), = 80.50(3)°, and Z = 2. The crystal structure consists of molecules of (Ph₃SiO)₃B and Ph₃SiOH linked by an weak B···(silanol) acceptor-donor bond, additionally stabilized by OH(silanol)···O(siloxy) hydrogen bonds. The average B–O, Si–O distances and B–O–Si angle are 1.369, 1.649 Å and 137.2°, respectively.     

水热法合成Zn1-xMnxO：Sn和Zn1-x-yMnxCoyO：Cu晶体的磁性

本文采用水热法,以ZnO为前驱物,添加适量的MnCl2·4H2O、SnCl2·2H2O和MnCl2·4H2O、CoCl2·6H2O、CuCl2·2H2O,3 mol/L KOH作矿化剂,430℃反应24 h,分别合成了Zn1-xMnxO:Sn晶体和Zn1-x-yMnxCoyO:Cu晶体.用扫描电镜(SEM)对合成物形貌进行分析,结果表明,Zn1-MnxO:Sn晶体为六棱柱状晶体,直径约为10 μm,较大面积显露正极面c{0001},同时也显露负极面-c{0001}、正锥面p{1011}、负锥面-p{1011}和柱面m{1010}.Zn1-x-yMnxCoyO:Cu晶体也显露负极面-c{0001}、正锥面p{1011}、负锥面-p{1011}和柱面m{1010},{0001}显露面小于{0001}.X射线能谱(EDS)分析表明晶体主要成分为ZnO,Mn2 、Co2 离子掺杂量超过2%;SQUID磁性测量显示所合成晶体在25 K具有反铁磁特征,高温为顺磁性.     

Crystal and Molecular Structure of 6,6′-Dimethoxy-gossypol:Acetic acid (1:1)

Abstract By crystallization from dilute solutions of acetic acid (2–4%) in diethyl ether, acetone, or methyl ethyl ketone, 6,6′-dimethoxy-gossypol forms a solvate with acetic acid in a one-to-one molar ratio. The compound crystallizes in the triclinic P space group and has unit cell dimensions of a = 7.5793(10) ?, b = 14.7211(19) ? and c = 14.740(2) ?, α = 106.260(3)°, β = 102.310(3)°, γ = 95.975(3)°, Z = 2. The structure was solved by direct methods and refined to an R1 value of 0.0394 on 4252 observed reflections. Enantiomeric pairs of dimethoxy-gossypol molecules form centrosymmetic dimers that are characterized by a pair of intermolecular hydrogen bonds and by hydrophobic stacking between pairs of naphthalene rings. The acetic acid molecule accepts a hydrogen bond from a gossypol hydroxyl group and donates to a hydrogen bond with one of the aldehyde groups of an adjacent gossypol molecule. Although there is less hydrogen bonding in this structure than in the gossypol:acetic acid (1:1) structure, the molecular packing of the two compounds is similar. Graphical abstract Crystal and molecular structure of 6,6′-dimethoxy-gossypol:acetic acid (1:1) Michael K. Dowd and Edwin D. Stevens The molecular structure of the acetic acid solvate of 6,6′-dimethoxy-gossypol is presented.      

AlN buffer layer growth for GaN epitaxy on (1 1 1) Si: Al or N first?

AlN is generally used as buffer layer for the epitaxial growth of GaN on Si(1 1 1) substrate. In this work, we specifically address the relationship between the way the AlN growth is initiated on the Si(1 1 1) surface and the overall properties of the final GaN epitaxial layer. The growth is performed by molecular beam epitaxy with ammonia (NH₃) as nitrogen source. Two procedures have been compared: exposing the Si surface first to NH₃ or Al. The AlN nucleation is followed in real-time by reflection high-energy electron diffraction and critical stages are also investigated in real space using scanning tunnelling microscopy and transmission electron microscopy. Atomic force microscopy, X-ray diffraction and photoluminescence are also used to assess the properties of the final GaN epitaxial layer. It is shown that best results in terms of GaN overall properties are obtained when the growth is initiated by exposing the Si(1 1 1) surface to NH₃ first. This is mainly due to the fact that almost an order of magnitude decrease of the dislocation density is obtained.     

Preparation and crystal structure of spiro(5,7-dimethoxy-1(1H)oxo-2-benzopyran-3(4H),1′-cyclohexane)

Spiro(5,7-dimethoxy-1(1H)oxo-2-benzopyran-3(4H),1-cyclohexane) (C₁₆H₂₀O₄) was prepared by alkylation of o-lithio 3,5-dimethoxy-N-methyl benzamide with methylene cyclohexane oxide followed by alkaline hydrolysis and its crystal structure was determined by X-ray crystallographic techniques. The compound crystallizes into monoclinic space group P2₁/c with unit cell parameters: a = 11.914(3) Å, b = 9.861(3) Å, c = 12.508(7) Å, = 91.34(3), Z = 4. The structure has been solved by direct methods and refined to R = 0.039 for 1870 observed reflections. The heterocyclic ring adopts distorted sofa conformation while cyclohexane ring assumes a highly symmetric chair conformation. The dihedral angle between the mean planes of isocoumarin nucleus and cyclohexane ring is 105.51(5). Molecules are held together in the crystal by C=H ... O hydrogen bonds.     

The crystal structure and IR spectra of μ-(bipyrimidine-N1,N1′,N5,N5′)-bis[(azido-N1)(methanol)(bipyrimidine-N1,N1′)copper(II)] bis(triflate) bis(methanol)

The structure of the title compound [Cu₂(bipym)₃(N₃)₂(CH₃OH)₂](CF₃SO₃)₂(CH₃OH)₂ has been determined by X-ray diffraction. The crystals are triclinic, space group P1, with a = 8.1844(5), b = 11.0253(6), c = 12.9089(7) Å, = 80.249(4), , = 74.933(5), = 74.001(4)°, and Z = 1. The structure consists of a dinuclear Cu(II) unit formed of two didentate bipym ligands, one bis-didentate bipym ligand, two azido anions, and two coordinating methanol molecules. The Cu(II) atom is elongated tetragonally surrounded by two nitrogens of the didentate bipym ligand, one nitrogen of the bis-didentate ligand, and one nitrogen of the azido anion forming the equatorial plane with one nitrogen of the bis-didentate ligand and an oxygen atom of the methanol molecule as the axial atoms. A noncoordinating triflate anion and an additional methanol molecule are also in the crystal lattice and have a hydrogen bond distance of 2.801(3) Å with an angle of 157(4)°. The cations link by O – H ··· N bonds into infinite chains running in the c-direction.