不同合成方法对LiMgPO4∶Dy发光性能的影响

分别采用高温固相法和溶胶凝胶法合成了LiMgPO₄和LiMgPO₄∶Dy,通过热重-差热热分析仪、X射线衍射仪、傅里叶红外光谱仪、场发射高倍扫描电镜、紫外可见分光光度计和荧光分光光度计研究了不同合成方法对LiMgPO₄∶Dy晶体结构、形貌和发光性能的影响。结果表明，溶胶凝胶法的最低合成温度为750℃且晶体中几乎不存在其他晶相，而高温固相法在950℃合成的晶体中仍然存在少量Mg₃(PO₄)₂晶相；相比于高温固相法，溶胶凝胶法合成的样品形貌比较规则；两种方法合成的样品在可见光区域光吸收能力差，而在紫外区域高温固相法合成的样品光吸收能力明显较高；高温固相法合成的LiMgPO₄∶Dy光学带隙范围为3.76～3.93 eV,溶胶凝胶法合成的LiMgPO₄∶Dy光学带隙范围为3.85～3.94 eV,合成方法对样品的光学带隙影响较小。LiMgPO₄∶Dy的最佳激发波长为350 nm,最强发射峰位于579...     

锰锌铁氧体材料的制备研究新进展

介绍了目前国内外制备锰锌铁氧体材料的主要方法及研究进展,包括传统的干法工艺(陶瓷工艺)和湿法工艺等,同时指出了各种制备方法的优缺点.认为煅烧条件的控制及产品粒径的分布是影响材料磁性能的关键,湿法工艺中的溶胶-凝胶法和水热法是今后研究的主要方向.     

Ⅲ-Ⅵ族InSe半导体晶体生长研究进展

Ⅲ-Ⅶ族InSe晶体是一种非常重要的化合物半导体材料,在高性能纳米电子器件、红外光探测、光电器件及柔性电子等领域有广泛应用。本文简要介绍了In-Se相图的发展历程,InSe具有非一致熔融特性,可通过包晶反应从准化学计量比或非化学计量比溶液中析晶获得,其中In/Se摩尔比对InSe转化率有重要影响。迄今,垂直布里奇曼法、提拉法、水平梯度凝固法、低温液相法及气相输运法等多种技术被成功用于制备InSe晶体。为全面了解InSe晶体生长的历史和现状,本文从工艺原理、技术要点、晶体生长结果等方面将国内外相关工作进行了梳理,并对各种方法的优缺点进行了比较。研究分析表明垂直布里奇曼法因对设备要求简单,操作简易,现已成为制备高质量大尺寸InSe晶体的主流技术;水平梯度凝固法则在ε型InSe晶体生长方面颇具特色,未来可在新材料性能研究与应用探索上与垂直布里奇曼法形成一定补充。     

用FDTD与高分辨率谱估计相结合计算二维声子晶体的能带

基于现代信号处理中的高分辨率谱估计方法,对用时域有限差分方法计算二维声子晶体能带的迭代过程所输出的数据序列做后处理.数值仿真结果表明,相对于基于Fourier变换的后处理方法,该后处理方法在保证对二维声子晶体本征频率的精确估算的同时,能明显减少时域有限差分方法的迭代步数.     

Single crystal growth of copper phthalocyanine using exaltation–evaporation growth method

A new method of growing single crystal for β-form copper phthalocyanine (CuPc) is presented in this paper. Melted anthracene was used as solvent of CuPc. The method, vaporizing the solvent using an automatic exaltation machine, was employed to grow CuPc single crystals. The needle-like single crystals of CuPc up to 11.6 mm in length were obtained by applying this method. The influences of different temperatures, exaltation speeds and concentrations on the single crystals growth were also discussed. The method was called exaltation–evaporation growth method.     

Investigation of the Microstructure of Crystals Surfaces by the Method of Self-decoration during Ion Bombardment

A method is developed for self-decoration with ion bombardment by which the surface structure of crystal samples is investigated. The existing surface structure of the objects, as well as the additionally developed structure after prolonged ion bombardment are visualized by this method. When using scanning electron microscopy the method allows multiple investigation of the sample or of one and the same parts of it respectively. The mechanism of the method is revealed by the results obtained in the performed experiments. It is proved that the crystal surface and its decoration depend on the peculiarities of the crystal structure and on the conditions of bombardment. By varying the conditions of ion bombardment the sensitivity of the method is considerably changed.     

Studies on conventional and Sankaranarayanan–Ramasamy (SR) method grown ferroelectric glycine phosphite (GPI) single crystals

Transparent single crystals of glycine phosphite were grown by Sankaranarayanan–Ramasamy (SR) method and conventional slow evaporation solution technique (SEST) which had the sizes of 100 mm in length, 30 mm diameter and 10×11×8 mm³. The conventional slow evaporation and Sankaranarayanan–Ramasamy method grown glycine phosphite single crystals were characterized using laser damage threshold, chemical etching, Vickers microhardness, UV–vis–NIR and dielectric analysis. The laser damage threshold value was higher in SR method grown GPI crystal as against conventional method grown crystal. The SR method grown GPI has higher hardness and also higher transmittance compared to conventional method grown crystal. The chemical etching and dielectric loss measurements indicate that the crystal grown by SR method has low density of defects and low value of dielectric loss compared to conventional method grown GPI crystal.     

Optimization Method of Direct Search and Its Application in Reflectometry and Grazing Incidence Diffraction

Crystallography Reports - A method of mathematical optimization is proposed to obtain an exact solution to the problem of finding the extremum. The method, called the direct search method,...     

A new method for determining the thickness and composition of thin layers by electron probe microanalysis

A new method is described which allows the determination of thickness and composition of thin layers by EPMA simultaneously. The method is based on new depth distribution functions of the characteristic X-rays and on a substrate correction which was developed by the authors. The test of this method with the aid of wellknown layers gives very good results. The method works with massive standards. Layers for calibration are not needed.     

Calculation of radial distribution function from incomplete experimental diffraction data

A method for calculating atomic radial distribution functions for amorphous materials has been suggested. The method is based on the principle of the maximum informational entropy. Under the condition of a limited amount of the experimental diffraction data, the method allows one to obtain the unique solution and considerably reduces the errors caused by series termination, which are inherent in traditional computational methods based on the Fourier transform. A criterion of using the method of optimum information is formulated, and the reliability of the data obtained are quantitatively estimated. The advantages of the method are demonstrated on the computation of the short-range order in hydrogenated amorphous silicon.     

Structure analysis by reduced data. III. Method of interexperimental minimization

Being logically justified, a new algorithm of the interexperimental minimization (IEM) has been formally described. The IEM method is the generalization of the optimization method to the case of several independent measurements and is characterized by the following basic features: (1) the structural model refined is divided into the basic model and the model-perturbation; (2) the goal function of the method has four terms, of which the first two correspond to independent measurements, the third one, to averaged measurements, and the fourth one, to the normalized interexperimental difference; (3) in the IEM refinement, the weighting scheme adequately reflecting the accuracy of the experimental data is automatically formed; (4) the interexperimental minimization method includes the algorithm for reducing interparametric correlations; (5) the basic criterion of the IEM method is the statistical test of reproducibility of the results; (6) the IEM method uses the quantum-mechanical and molecular-dynamics calculations to normalize the experimental data; and (7) the physical reliability of the results obtained upon the refinement by the IEM method also depends on the coupling relations imposed onto the structural and functional parameters.     

NaYbF4纳米晶浓度调节方法研究

本文采用热分解法制备了NaYbF₄纳米晶.通过TEM图像对NaYbF₄纳米晶的尺寸进行表征.根据Beer-Lambert理论建立了NaYbF₄纳米晶浓度与其光吸收度间的关系.提出了NaYbF₄纳米晶浓度调节方法,利用NaYbF₄纳米晶中Yb³⁺的吸收光谱确定溶液中NaYbF₄纳米晶的浓度,并给出了纳米晶浓度调节公式.为了检验这种浓度调节方法,对五批次NaYbF₄纳米晶样品的浓度进行调节,发现浓度调节方法非常可靠.并对调整后的浓度进行多次测量,检验此调节方法的误差,最大误差在9;.     

Polarization and Viscosity Measurements in a Ferroelectric Liquid Crystal by the Field Reversal Method

With the aim to develop a standard method for measurements of the polarization of ferroelectric chiral smectic C liquid crystalline materials, we have studied thin, well-aligned samples of MBRA-8 using the field-reversal method. The method also provides an estimate for the rotational viscosity and for the response times.     

Graphical method for the Debye-like relaxation spectra analysis

In this study a new graphical method for the dielectric relaxation spectra analysis is presented. The method is based on the graphical determination of characteristic segment values. The Debye, Cole–Cole, Davidson–Cole, Havriliak–Negami distributions are analyzed using the suggested method. The relationships between the segment values and the parameters of distributions are found. The method is more simple and informative in comparison with the Cole–Cole diagram.     

Conoscopic optical method of determining liquid crystal low tilt angles

A simple conoscopic optical method of determining liquid crystal low tilt angles with sufficient accuracy for many practical purposes is described. The similarity between this method and the crystal rotation one is shown. The limits of applicability of the conoscopic optical method are also given.     

Über Gitterstörungen,Debye-Temperatur und Grenzfrequenz von mechanisch aktiviertem Aluminiumpulver

The lattice distortion of mechanically activated aluminium powder has been measured by the method of FRICKE and GWINNER and by the single-temperature method. Both measurements give analogous functions but different values. By the single-temperature method it is possible to determine both the Debye-temperatur and the Debye frequency.     

A linear relativistic method for the calculation of band structure in transition metals with results for Au

With a linear relativistic method we calculated the band structure of gold. A comparison with the results of a RAPW calculation shows that the deviation is about 3%. The effort of computational time is for the linear method considerably smaller than for the RAPW method.     

液相沉淀法制备硅酸镥粉体的研究

将氯化镥溶液滴加至硅酸钠溶液中制备出的沉淀,经过滤、陈化及烘干后对其进行XRD成分及SEM显微形貌的分析,结果表明粉体除少量杂质外,其主要成分都是由硅酸镥构成,而经烘干研磨后的粉体颗粒呈球形,将采用液相沉淀法与固体混合焙烧法所制备出的两种粉体进行了对比发现,采用前者可以不经高温煅烧就可以得到较纯硅酸镥,而后者在较高温度下煅烧后仍有大量原料残余,而且从颗粒尺寸、粉体形状以及烧结性能上来液相法制备出的粉体看都优于固相法.     

Diamond Synthesis in Cool Plasma

The conditions of low pressure autoepitaxy of diamond are analysed and theoretical concepts concerning the plasmochemical method of diamond synthesis put forward. The experimental method used is described. The obtained results have demonstrated the utility of the plasmochemical method for obtainment of diamond and confirmed the validity of the presented theoretical concepts.     

New method for measuring rocking curves in X-ray diffractometry by ultrasonic modulation of the lattice parameter

A method for measuring double-crystal rocking curves with the aid of an X-ray-acoustic analyzer is proposed and implemented. This method makes it possible to perform precise measurements with a high time resolution and without the mechanical rotation of the crystal. The results of testing the method are presented.