畸变钙钛矿结构的晶体定向转换方法与应用

钙钛矿结构的复杂氧化物因其丰富的物理性能而成为研究热点.本文选取了SrTiO3、BiFeO3、NdGaO3三种钙钛矿结构的氧化物材料,运用透射电镜、JEMS软件模拟等方法研究其晶体结构转换关系.通过对正交、菱方畸变的钙钛矿结构进行立方定向转换的具体方法做理论推导,得到了三种定向之间的转换矩阵,并结合电子衍射、模拟、高分辨像验证了推导结果.我们的研究为畸变钙钛矿结构材料统一为等效立方晶胞讨论提供了依据.     

The Polytypoidic Structure of the High-Tc Superconducting System Bi2Sr2Can–1CunO2n+4 and its Superconductivity

The polytypoidic structures in the Bi-system of superconductors characterized by X-ray, electron diffraction and TEM technique are described. A strong incommensurate modulated diffraction was observed by these methods in the 2223-phase. In addition, we revealed the Laue streaks for the one-dimensional disorder, the banded structure perpendicular to the c-axis. We suppose that the intergrowth is an indication of the displacement in the Bi-O layers. It is evident that the polytypoidic concept allows us to describe the structure and physical properties of these superconducting phases in a unified manner. So it is shown that the polytypoidism is a general feature of the Bi-system materials.     

Crystal Structure and Ferromagnetic Component in Layered Perovskite Sr0.8Y0.2CoO2.65

Crystallography Reports - The crystal structure and magnetic state of Sr0.8Y0.2CoO2.65 layered perovskite have been studied using neutron diffraction and synchrotron radiation diffraction and...     

Crystal Structure of Rabdoternin A

Abstract  

Rabdoternin A is a natural diterpenoid isolated from Rabdosia rubescen and its crystal structure was determined by X-ray single crystal diffraction. The compound compactly packs in an orthorhombic unit cell in the P2₁2₁2₁ space group with unit cell dimensions a = 7.9200(10) ?, b = 11.2411(14) ?, c = 20.474(2) ?, V = 1822.8(4) ?³ and Z = 4. Two intermolecular hydrogen bonds assemble the title compound into infinite two-dimensional networks along (001) plane.     

钙钛矿单晶的合成研究进展

钙钛矿材料优异的光电性能使钙钛矿太阳能电池成为目前发展速度最快的光伏技术之一。近期的研究发现无晶界的单晶钙钛矿薄膜拥有更低的缺陷密度、更高的载流子迁移率、更长的载流子复合寿命,并且还有较高的稳定性和更宽的光吸收范围,因此有望制备出更高效且更稳定的钙钛矿太阳能电池。本文简要介绍了单晶钙钛矿太阳电池的基本结构及其发展历程,着重介绍了有关单晶钙钛矿薄膜和块状单晶钙钛矿的制备方法,并且对不同方法制备的单晶钙钛矿太阳能电池的效率进行了比较,最后对单晶钙钛矿太阳能电池当前存在的问题以及未来发展进行了简要分析和展望。     

模拟铀在钙钛矿中的晶格固化研究

以分析纯CaCO3 、TiO2和CeO2为原料,铈作为铀的模拟元素,通过高温固相反应,在1300℃下保温2h合成了不同Ce掺量的钙钛矿固化体.采用XRD对固化体进行物相分析,同时使用Rietveld全谱拟合方法对其晶体结构进行研究,并用SEM和EDS对固化体的微观结构与成分进行了表征.结果表明,固化体中Ce核素只进入钙钛矿晶格形成固溶体,其中钙钛矿对Ce核素的包容量低于23.21wt;,约为0.2 ～0.25个结构单位;Ce核素掺入后导致钙钛矿晶体结构发生畸变,晶胞参数a、c和晶胞体积V随Ce核素含量的增加而增大,固化体整体上仍保持稳定的钙钛矿晶体结构;SEM分析显示Ce核素的掺入促进了固化体晶粒的长大,且晶粒之间紧密堆积,使得其密度增大、气孔率降低;EDS分析表明A2和A4样品Ce核素的统计平均包容量分别为11.19wt;和19.84wt;,验证了XRD与Rietveld结构精修的分析结果.     

A New Crystal Structure of Clarithromycin

Abstract A new crystal structure of clarithromycin single acetonitrile solvate designated “Form III” was first determined by single crystal X-ray diffraction. The compound crystallized in the monoclinic system, P2 ₁ space group with a = 10.644(2) ?, b = 18.099(4) ?, c = 11.628(2) ?, α = γ = 90°, β = 95.38(3)°, V = 2230.1(8) ?³, Z = 2, D _c = 1.175 g/cm³, μ = 0.087 mm⁻¹, F(000) = 860, R ₁ = 0.034, wR ₂ = 0.062, S = 0.875, (Δ/σ)_max = 0.001 for 2,709 observed reflections (I > 2σ (Ι)). Form III of clarithromycin, contrary to Form I, is more thermodynamically stable than Form II used currently on the market. Graphical abstract A New Crystal Structure of Clarithromycin Jian-Hua Liang, Guo-Wei Yao A crystal structure of clarithromycin single acetonitrile solvate was first determined by single crystal X-ray diffraction.      

一种新颖的磁控溅射纯Cr薄膜结构区域模型

磁控溅射成膜过程中,基于溅射中性原子对基片表面微区的轰击效应Ec11和各种轰击离子对基片微区表面的轰击效应Ec22两个能量因子建立了磁控溅射纯Cr薄膜的结构区域模型,研究发现磁控溅射系统中较高的离子流密度显著影响着薄膜的微观结构,且可在较低的相对温度下促进完全致密薄膜结构的形成.     

A Simple Method to Realize the Atomic Structure of Crystal Faces

A simple method for the determination of the atomic structure of crystal faces is proposed. Its application is given by way of the investigation of some Iceland spar crystal faces being of great technical interest.     

Mg1-xNaxB2的结构和超导特性研究

在Ar气保护条件下,采用烧结扩散反应法制备了不同钠含量的Mg1-xNaxB2块状样品.用X射线衍射及SQUID磁强计对样品进行了分析.X射线衍射检测结果表明样品中除了MgO杂相之外,主要为晶态MgB2物相.SQUID测量结果表明:钠的掺入仅使MgB2超导转变温度稍有降低.同时发现在样品的烧制过程中,多于化学计量比的Mg粉并没有影响到超导的转变温度及转变温度的宽度.     

PbLa（ZrSnTi）O3弛豫反铁电单晶的畴结构与成畴机制

使用助熔剂法生长了PbLa(ZrSnTi)O3弛豫反铁电单晶,使用偏光显微镜对单晶中的畴进行了观察。结果表明,在(001)面上,PbLa(ZrSnTi)O3单晶中存在[110]走向和[110]走向的畴,以及[100]走向和[010]走向的亚畴。对PbLa(ZrSnTi)O3单晶的成畴机制进行了分析,引入微区应力成畴机制解释了单晶中[110]走向和[110]走向的畴结构,而对[100]走向和[010]走向的亚畴结构则要同时考虑极性微区中自发极化的影响。     

零维钙钛矿结构Cs3Cu2Br5单晶的生长和X射线探测性能

金属卤化物低维钙钛矿具有高效的发光性能,并且作为闪烁体在辐射探测领域表现出极大的潜力。本文采用布里奇曼坩埚下降法生长出全无机零维钙钛矿结构Cs₃Cu₂Br₅单晶。研究了Cs₃Cu₂Br₅的光学吸收、光致激发和发射,时间分辨光致发光和以及X射线探测性能。Cs₃Cu₂Br₅晶体结构为正交晶系,空间群为Pnma。在X射线激发下,Cs₃Cu₂Br₅晶体具有峰值约为467 nm的宽带发射,该发射来自自陷激子发射。Cs₃Cu₂Br₅的稳态光产额约为4 000 ph./MeV,且X射线余辉性能表现与BGO晶体相当。     

A Polymorph Crystal Structure of Hexaphenyl Observed in Thin Films

Highly oriented thin films of hexaphenyl — which are used in organic opto‐electronic applications — are characterised in terms of their crystal structures. Two different crystal structures of hexaphenyl (C₃₆H₂₆) are observed when the films are prepared by physical vapour deposition at various substrate temperatures. If the substrate is kept at room temperature, hexaphenyl crystallises within a structure which is already known from single crystal investigations. However, when the thin films are grown at a substrate temperature of 160°C a new crystalline phase appears. This structure was characterised by X‐ray and transmission electron diffraction. Due to the strong preferred orientation of the crystallites within the thin films, the lattice constants as well as main features of the new crystal structure could be determined. The lattice is indexed as monoclinic with: a = 7.98Å, b = 5.54Å, c = 27.64Å and β = 99.8°. The new crystal structure has high similarity to the already known crystal structure: Both structures are built by layers of hexaphenyl molecules, within one layer the aromatic planes of the hexaphenyl molecules are packed in a herringbone pattern. The characteristic feature of the new structure is that the long axes of the hexaphenyl molecules are arranged absolutely perpendicular to the layers, whereas, within the already known structure the long axes show an tilt angle of 17° to the layer normal direction.     

Crystal Structure of Microclusters of Silver

Finding the crystallographic structure of clusters is a crucial and challenging problem. The properties like lattice concentration, unusual crystal symmetries etc. of metal clusters have been studied recently. We report here a 15% lattice concentration for silver clusters produced by Bredig's method.     

Crystal and Molekular Structure of Piperidinium-acet-p-Cl-anilide-chloride

Piperidinium-acet-p-Cl-anilide-chloride crystallizes in the triclinic space group P 1 with 2 formula units C₁₃H₁₈ON₂Cl₂ in the unit cell. The lattice constants are a = 10.471 Å, b = 12.545 Å, c = 6.149 Å, α = 72.14°, β = 105.70° and γ = 105.21°. Bond lengths, bond angles and the conformational flexibility were determined by X-ray structure analysis. The crystal structure contains dimeres consisting of drug molecules connected by hydrogen bonds.     

Crystal Structure of Glycinium Dicitratoborate Monohydrate

Crystallography Reports - Crystals of glycinium dicitratoborate monohydrate H3NCH2COOH[B(C6H6O7)2] · Н2О have been synthesized and selected for the first time. Their structure is...