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.     

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.     

A Direct Method for the Determination of Orientation Relationships Using TEM

A new method for the determination of orientation relationships has been developed. The method is based on a recently proposed direct method for orientation determination using a transmission electron microscope (TEM). The determination of the orientation relationship can be done by two different but generally applicable approaches. The first approach is especially applicable for crystals with orthogonal base vectors, the second approach is especially applicable for crystals with non-orthogonal base vectors and the general bicrystal.     

基于Micro-LED全彩色微显示器制造技术研究进展

Micro-LED作为新一代显示技术,具有高亮度、低能耗、长寿命、自发光等优点,但其低效率全彩色显示等技术瓶颈限制了其产业化的进程和普及率的上升。全彩色显示是micro-LED商业化的关键技术,但随着LED芯片的高度集成化和微小化,将巨量的RGB三色芯片转移到同一衬底上实现全彩色显示的方法很大程度上造成了高成本和低成品率。因此,亟需发现更为简便和高效的全彩色显示方法。本文就micro-LED微显示器的制作技术及其实现全彩色显示的方法进行综述,重点介绍了量子点颜色转换层法、RGB直接排列法、特殊结构法和光学透镜法,最后探讨了micro-LED微显示器的技术挑战及发展趋势。     

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.     

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。     

Growth of TGS crystals using uniaxially solution‐crystallization method of Sankaranarayanan‐Ramasamy

The recently discovered crystal growth method called uniaxially solution‐crystallization method of Sankaranarayanan–Ramasamy (SR) is modified in some aspects and used for growth of triglycine sulphate (TGS) crystals. The modification leads to the simplicity, reduction of cost and avoided the temperature fluctuations. The 〈010〉 direction of TGS is very important and used for fabrication of infrared detectors. Using this method, the 〈001〉, 〈010〉 directional crystals of TGS were successfully grown in a glass crystallizer. The grown crystal was characterized by HRXRD, UV‐Visible and dielectric studies. The results prove the suitability of the modified SR method for oriented TGS crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On calculation of the transformation kinetics for models with the diffusional law of growth of new-phase precipitates

A method of calculation of the transformation kinetics for the geometric probability model with continuous nucleation and diffusional growth of new-phase precipitates is described. Previously, this method made it possible to calculate very exactly (with a level of error no greater than 0.00011) the evolution of the volume fraction of the non-transformed phase. It is shown that the upper bounds for the volume fraction of the nontransformed phase published recently for this model are much less accurate. The theoretical basis of the proposed calculation method is discussed.     

硒化镉多晶原料的提纯

采用改进的垂直无籽晶气相法生长大尺寸高质量的CdSe单晶体要求原料的纯度高。本文根据差热(DIA)和热失重(TG)测试结果，设计出连续抽空区域升华提纯CdSe原料的新方法，用该方法提纯的原料生长出大尺寸、高质量的GtSe单晶体。等离子体质谱仪(ICP-MS)分析结果表明，新方法对CdSe的提纯是有效的，纯化后的原料可以生长出大尺寸高质量的CdSe单晶体。     

Determination of the Effective Kinetic Diameter of the Complex Molecules

A method for the estimation of the effective kinetic diameter of the complex molecules is suggested. The method is based on the construction of a geometrical model by using the known data for the internuclear distances and atomic radii. On the basis of the suggested method the values of the effective kinetic diameter of some molecules for which there are no respective experimental data are calculated.     

Structure analysis by reduced data: V. New approach to refinement of crystal structures

A new approach to refining crystal structures using reduced experimental data is considered. The data reduction, which requires the establishment of the common and different characteristics of the measured data, can be done using the method of interexperimental minimization. The method is used to analyze the thermal motion of atoms. The method can also be used for the detailed study of different groups of those model parameters that are especially important for each specific case.     

Indexing of double reflection peaks

A numerical and a graphical method for indexing double reflections is described. The conditions for the applicability of the graphical method are discussed.     

基于钠助熔剂法的GaN单晶生长研究进展

宽禁带氮化镓(GaN)材料以其独特的性质和应用前景成为国内外研究的热点,高质量GaN单晶衬底的制备是获得性能优异的光电子器件和功率器件的基础。钠助熔剂法生长条件温和,易获得高质量、大尺寸的GaN单晶,是一种具有广阔商业化前景的GaN单晶生长方法。钠助熔剂法自20世纪90年代末期被发明以来,经过20多年的发展,钠助熔剂法生长的晶体在尺寸与质量上都取得了长足的进步。本文从晶体生长原理和关键工艺(籽晶选择、温度梯度以及添加剂)等方面综述了钠助熔剂法生长GaN单晶研究进展,并对其面临的挑战和未来发展趋势进行了展望。     

Atomic force microscopy modified for studying electric properties of thin films and crystals. Review

Probe force microscopy continues growing in popularity as a method for studying surfaces of solids and control over crystals and thin films that are grown on various scientific and industrial setups. New modifications of the method increase the possibilities for recording various characteristics of the objects studied. An important role here is played by “electrical” force microscopy, the various modifications and practical applications of which are considered below, as well as the results obtained by this method.     

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.     

Optimization of the calculation of a local electric field in crystals by the transient-region method

The specific features of using the method of transient-region for calculating local electric fields and the corresponding potentials are considered on examples of the calculations for NaF, CsCl, and LiNbO₃ crystals. It is shown that for crystals with a primitive cubic lattice, this method can provide any given accuracy of the calculated Madelung constant; for displacive-type ferroelectrics (LiNbO₃), the method allows the calculation of the local electric field with a very high accuracy. It is emphasized that for each specific object, one has to carefully select the parameters of the convergence function.     

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.     

Efficient solution of a batch crystallization model with fines dissolution

In this paper, an efficient and accurate numerical method is proposed for solving a batch crystallization model with fines dissolution. The dissolution of small crystals (fines dissolution) is useful for improving the quality of a product. This effectively shifts the crystal size distribution (CSD) towards larger crystal sizes and often makes the distribution narrower. The growth rate can be size-dependent and a time-delay in the dissolution unit is also incorporated in the model. The proposed method has two parts. In the first part, a coupled system of ordinary differential equations (ODEs) for moments and solute mass is numerically solved in the time domain of interest. These discrete values are used to get growth and nucleation rates in the same time domain. In the second part, the discrete growth and nucleation rates along with the initial CSD are used to construct the final CSD. The analytical expression for CSD is obtained by applying the method of characteristics and Duhamel's principle on the given population balance model (PBM). A Gaussian quadrature method, based on orthogonal polynomials, is used for approximating integrals in the ODE-system of moments and solute mass. The efficiency and accuracy of the proposed numerical method is validated by a numerical test problem.     

Modeling habit forms of sapphire crystals using the principles of periodic-bond-chain method

The potential of the periodic-bond-chain method for calculating the sequence of manifestation of faces of corundum single crystals is considered. The leading role of the faces of the pinacoid, high rhombohedron, and hexagonal prism is demonstrated. The calculation results are compared with the experimental data on faceting the lateral surface of cylindrical sapphire single crystals grown by the Stepanov method and with the faceting data for crystals grown by the flux method and natural crystals.

     

Interferential method for determining the inclination angle of molecules in plane-parallel liquid crystalline layers

The interferential method is presented for determining the inclination angle θ of molecules in homogeneously ordered plane-parallel liquid crystalline layers. The essence of the method is the analysis of the changes in the layer transmission caused by the change in conditions of interference. The angle θ is calculated from the exact, explicit relation where from no limitations the size of the angle results. The measuring-stand is described that enabled the method to be put into practice. The results for the PCB layer are presented by way of example.