高精度X射线双晶衍射仪的原理及其应用

本文介绍了Ｘ射线双晶衍射仪的特点及其原理，以及利用Ｘ射线摇摆曲线技术在半导体材料研究方面的应用。     

X射线多晶面探测器衍射系统及其应用

介绍了目前世界上先进的粉末衍射系统——X射线多晶面探测嚣衍射系统的主要配置、工作原理、二维衍射几何关系以及X射线多晶面探测器衍射系统在材料学研究中的典型应用，重点讨论了在金属的晶体学织构和应力研究中的应用。     

Gd2O2SO4粉体的合成及其晶体结构确定

通过750℃,2h煅烧Gd2O3和H2SO4(摩尔比1:1)的前驱体方法合成了Gd2O2SO4粉体.利用Gd2O2SO4的X射线粉末衍射数据和Material Studio 4.0 Reflex模块中Powder solve技术和Rietveld精修方法对Gd2O2SO4的晶体结构进行了研究.研究表明:Gd2O2SO4具有空间群为PMNB(62)的正交晶系,晶胞参数为a=1.2996nm,b=0.8117nm,c=0.4184nm,V=0.440698nm3,Z=4,计算密度为6.6949g/cm3,并确定了晶胞中原子的位置,Rietveld精修得到的Rwp=9.15%.     

退火对氧化锌薄膜结晶性能的影响

采用射频磁控溅射法在(001)硅片上制备了ZnO薄膜,利用X射线衍射对薄膜的制备工艺进行了研究,结果表明,基板温度、溅射功率、氩氧比、总气压在一个较大的范围内变化时都可实现薄膜的c轴择优取向生长.随后对薄膜进行了空气退火并利用摇摆曲线表征薄膜的结晶质量,摇摆曲线的半高宽随退火温度的提高而减小,700℃退火后FWHM为2.5°.     

Mn掺杂的NaxCoO2多晶制备与电输运性质研究

采用固相反应法制备了沿(00l)面高度择优取向的γ相NaxCoO2(X=0.5+δ,0.7)和Na0.5+δCo0.95Mn0.05O2系列多晶,且微量Mn掺杂阻碍了晶粒的长大.77～300K电阻率-温度曲线表明,NaγCoO2为金属的电输运行为,在相同烧结工艺下,Mn掺杂导致Na0.5+δCo0.95Mn0.05O2...     

MnxCd1-xIn2 Te4晶体生长研究

采用Bridgman法生长四元稀磁化合物半导体Mn0.22Cd0.78In2Te4晶体。当晶体生长到预定长度时，淬火得到固液界面。采用光学显微镜、扫描电镜、X射线衍射仪、ISIS能谱仪以及Leica定量金相分析仪研究了晶体中出现的界面形态、相的和数量以及沿生长方向的相析出规律，并进行了相成分分析。研究发现，淬火得到的Mn0.22Cd0.78In2Te4晶体中存在两个界面，其中一个为固液相变界面，另一个为由α＋β两相区发展到单相β区时的转变界面，二者相对于生长初始端均为凹形；α＋β两相区中，β相以条状、花状和近似圆片状形式存在，其中条状β相多分布在晶界处；越接近生长初始端，花状和近似圆片状β相越小，条状β相越细，它们的含量越少；X射线衍射图谱表明，β相为黄铜矿结构，α相为面心立方结构。     

单晶取向及其分布两种测定方法的对比

单晶取向的判断是单晶生长和加工过程中的重要环节，比较研究了摇摆曲线法和旋转定向法两种测定方法在判断单晶取向性问题中的优缺点。结果表明：对于生长较好的单晶材料，摇摆曲线法定义材料结晶质量的准确性较高；而旋转定向法能很好地解决取向性材料晶面间距相同的重叠峰的分离问题。     

基于InP衬底的应变和应变补偿的InGaAs／InAlAs材料的高分辨X射线衍射分析

高分辨率X射线衍射技术被用来分析基于InP衬底的应变的InGaAs和InAlAs单层材料和应变补偿的InGaAs/InAlAs超晶格材料.通过倒空间mapping得到的单层材料的错向角大约为10-3度,可以忽略不计.通过摇摆曲线得到了单层材料的组分和体失配度,接着单层材料的结果被用来分析在相同的条件下利用MBE技术生长的超晶格材料.利用倒空间mapping精确得到了超晶格的平均垂直失配度和各层的厚度,通过X射线模拟软件得到的超晶格材料的模拟曲线和实测曲线吻合的很好.     

MOCVD方法在TiO2纳米粉末制备中的应用

众所周知，ＭＯＣＶＤ方法是制备薄膜材料的重要方法之一，现已广泛应用于半导体薄膜，铁电薄膜和超导薄膜等的制备。在以前的工作中，我们设计，加工安装，调试，建立了一套可计算机自动控制的热壁低压ＭＯＣＶＤ设备，制备了ＴｉＯ２纳米粉末，得到了一些初步结果。本文详细研究了热壁低压ＭＯＣＶＤ方法在ＴｉＯ２纳米粉末制备中的应用，通过的合理设计反应室和收集区域，在采用反应区域和收集区域之间无任何过渡区域的收集方式，     

等质量吸收系数物相的定量分析研究

用定性分析的方法,做出定量分析的结果。本文提出一种等质量吸收系数物相的快捷定量分析方法,并用实验加以验证。     

大直径Hg_3In_2Te_6晶体生长与性能表征

采用垂直布里奇曼法,成功生长出大直径Hg3In2Te6(Φ=30mm)晶体。通过傅立叶红外透射光谱测试了晶锭不同部位的红外透过率,并利用X射线双晶摇摆曲线表征了晶体的结晶质量。结果表明,定向切割晶片为(111)面单晶,衍射峰位于θ=12.1665°处,半峰宽为0.0760°;中部单晶片红外透过率平均值为50%,接近Hg3In2Te6晶体的红外透过率最大值57%。位错和成分非均匀性是造成晶锭不同部位红外透过率差异的主要因素。     

Facile synthesis and crystal growth dynamics study of MgAl2O4 nanocrystals

Well-dispersed MgAl₂O₄ nanocrystalline was prepared by a convenient salt-assistant combustion process using low-toxic glycine as fuel, low-cost Mg(NO₃)₂·6H₂O and Al(NO₃)₃·9H₂O as raw materials. By changing the reaction condition such as glycine dosage, the amount of inert-salt, inert-salt types and calcinations temperature, the optimal conditions to synthesize MgAl₂O₄ nanocrystalline were explored. The obtained results showed that parameters inert-salt and fuel dosage in the process have an important effect on the structure properties of samples. The obtained products were characterized by XRD and TEM. TEM images revealed that the products were composed of well-dispersed cube-like nanocrystals with the size of 60–80 nm. The synthesis mechanism of MgAl₂O₄ nanocrystals was discussed. The crystal growth dynamics of MgAl₂O₄ nanocrystals was studied and the activation energy of MgAl₂O₄ nanocrystals was 39.1 kJ/mol.     

High-quality crystal growth and characterization of organic nonlinear optical crystal: 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST)

High quality 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystal has been successfully grown from saturated methanol solution by a slow cooling method in a Teflon vessel. The full width at half maximum (FWHM) of (001) X-ray diffraction (XRD) rocking curve depends on the growth rate, and the FWHM could be decreased to 15·8 arcsec. Close relation was observed between the mechanical property and crystallinity. The Vickers hardness increased up to 49 on decreasing FWHM.     

Physicochemical properties and theoretical explanation of ZnCd(SCN)4 crystal

The crystal density and Mohs hardness of zinc cadmium thiocyanate (ZCTC), ZnCd(SCN)₄ have been measured at room temperature. The specific heat of the crystal is 699.5 J mol⁻¹ K⁻¹ at 300 K. The thermal expansion coefficient (TEC) along the a and c axes, respectively, is interpreted on the basis of crystal structure. The thermal decomposition process is characterized by thermogravimetry analysis and differential scanning calorimetry (TGA/DSC). The intermediates and final products of the thermal decomposition were identified by X-ray powder diffraction at room temperature. The high-temperature effect in air on the optical transmission of the crystal was also studied.     

氮化锌空心粉末的制备和表征

报道了氮化锌空心粉末的制备和表征。将纯Zn粉置于流量为500mL／min的NH3气流中,在600℃温度下氮化150min,制备出Zn3N2空心粉末。用X射线衍射（XRD）和扫描电子显微镜（SEM）对制备的Zn3N2空心粉末进行了确认、观测和表征。     

Single crystal growth of Mn2N using an In-Na flux

Hexagonal platelet and pyramidal single crystals of Mn₂N were prepared by using an In-Na flux at 700 °C and 5 MPa of N₂ pressure. The crystal structure (space group P6₃/mmc) with lattice parameters a=2.8185(6) Å and c=4.5371(12) Å was confirmed by X-ray single-crystal diffraction. Nitrogen atoms statistically occupy a half of the octahedral interstitial sites in a hexagonal closest packing arrangement of Mn atoms.     

Oxygen pressure dependent VO2 crystal film preparation and the interfacial epitaxial growth study

High quality VO₂ crystal films have been prepared on sapphire substrates by pulsed laser deposition method and the effects of oxygen pressure on the crystal phase structure are investigated. Results indicate that the phases and microstructures of VO₂ films are strongly sensitive to oxygen pressure. High oxygen pressure tends to form coarse B-VO₂ nanocrystals while low pressure favors a flat M1-VO₂ film epitaxial growth. X-ray diffraction φ-scan patterns confirm the [020] epitaxial growth orientation of the M1-VO₂ film and the in-plane lattice epitaxial relationship at the interface is also examined. Raman spectra indicate that M1-VO₂ phase has much stronger Raman scattering modes than B-VO₂, and the clear phonon modes further confirm the idea stoichiometry of VO₂ crystal film. Infrared transmittance spectra as the function of temperature are recorded and the results show that M1-VO₂ crystal films undergo a distinct infrared transmittance variation across metal insulator transition boundary, while B-VO₂ exhibits negligible thermochromic switching properties in the temperature range concerned. The pronounced phase transition behavior of the M1-VO₂ crystal film makes it a promising candidate for optical filter/switch and smart window applications in the future.     

Phase formation mechanism and kinetics in solid-state synthesis of undoped and calcium-doped lanthanum manganite

LaMnO_3+δ and La_0.7Ca_0.3MnO₃ were synthesized from La₂O₃(La(OH)₃), CaCO₃ and MnO₂ powder mixture with solid-state reaction technique. X-ray diffraction and thermal analysis were employed in the present study on the process of synthesizing of the two compound powders. The kinetic study on solid-state reaction between La₂O₃ and MnO₂ in the powder mixture was isothermally carried out for LaMnO_3+δ formation. The result showed that the reaction process was controlled by three-dimensional solid-ionic diffusion. Both Jander and Ginstling-Brounstein model can be used to describe the reaction kinetics satisfactorily. The relevant apparent activation energy values obtained were as great as 205 ± 11 and 189 ± 8 kJ/mol. The reaction process of La_0.7Ca_0.3MnO₃ preparation from La₂O₃, SrCO₃ and MnO₂ powder mixture was also studied using X-ray diffraction and thermal analysis. The result indicated that the following steps composed the overall reaction: the decomposition of the reactant; the formation of La_1−xCa_xMnO_3+δ; La₂O₃ and Mn₃O₄ reacted with La_1−xCa_xMnO₃ to form final La_0.7Ca_0.3MnO₃ phase. The latest step was the most time-consuming one among others in the overall reaction.