Spectra Analysis of a Novel Ti-Doped LiAlO2 Single Crystal

LiAlO2 single crvstals doped with Ti at concentration 0.2at.% are grown by the Czochralskl technique with dimensions φ42×55mm. Ti ions in the crystal are quadrivalence proven by comparing the absorption and fluorescence spectra of pure LiAlO2 and Ti： LiAlO2. After air and Li-rich atmosphere annealing, the absorption peaks in the range of 600-800nm disappear. We conclude that 682 and 756nm absorption peaks are attributed to the VLi and Vo absorptions, respectively： The peaks at 716nm and 798nm may stem from the VLi^＋ and absorptions. The colour-centre model can be applied to explain the experimental phenomena. Ti^4＋-doping produces more lithium vacancies in the LiAlO2 crystal. The intensities of [LiO4] and the associated bonds remain unchanged, which improves the anti-hydrolyzation and thermal stability of LiAlO2 crystals.     

Electronic Properties of Red P-Type Tl2S5 Single Crystals

Single crystals of red Tl2S5 were prepared by a special modified vertical Bridgman and Stockbarger technique.This growth was performed in our laboratory. The influences of temperature on the electrical conductivity, Hall mobility, carrier concentration, and thermoelectric power (TEP) were carried out in the temperature range 277-413K. Throughout these measurements, various physical parameters such as effective mass of charge carriers,carrier mobility, diffusion coefficient, and the relaxation time for both majority and minority carriers were found.     

胆甾-4α-甲基-8-烯-3β，7α-二醇二乙酸酯的结构与性质研究

Lophenol, cholest-4α-methyl-7-en-3β-ol (1), obtained from Dracaena cochinchinensis (Lour.) S. C. Chen, was structurally modified. It was acetylated to protect 3β-hydroxyl group, and then oxidised by selenium dioxide in acetic acid to give cholest-4a-methyl-8-en-3β, Ta-diol diacetate (3). This compound 3 is unstable in chloroform solution or when heated and easily converted to a diene compound, cholest-4a-methyl-7,14-dien-3β-ol acetate (4). The structures of 3 and 4 were elucidated by means of IR, ^1H NMR, ^13C NMR and MS, and the absolute configuration of 3 was established by X-ray crystallography. The property of 3 was also discussed in this paper. Both 3 and 4 are new compounds and were reported for the first time.     

Effect of Metallic Film in Diamond Growth from an Fe—Ni—C System at High Temperature and High Pressure

The metallic film surrounding a diamond single crystal,which plays an important role the diamond growth from and Fe-Ni-C system,has been successfully investigated by using transmission-electron microscopy(TEM),Raman layer(near diamond)of the film by TEM and Raman spectroscopy,but a parallel relationship exists between the(111) plane of γ-(Fe,Ni) and the (100) plane of (Fe2Ni)3C in this region.Compared with that of the film has an increase of 0.9V.According to the microstructures on the film obtained by the TEM.Raman spectra,and XPS,the catalytic mechanism of the film may be assumed as follows.In the surface layer of the film,iron and nickel atoms in the γ-(Fe,Ni) lattice can absorb carbon atoms in the (Fe,Ni)3C lattice and make them transform to an sp^3-like state.Then carbon atoms with the sp^3-like structure are separated from the (Fe,Ni)3C and stack on the growing diamond crystal.This study provides a direct evidence for the diamond growth from a metallic catlayst-graphite system under high temperature and high pressure.     

Low-Temperature Specific Heat of the Underdoped La2-xSrxCuO4 Single Crystals

We report the low-temperature specific heat of La2-xSrxCuO4(x=0.063) single crystals before and after annealing in the temperature region of 2-10K and magnetic fields up to 12T.The data confirm the √H dependence of the linear term coefficient γ predicted for d-wave paring in the Volovik theory at T=0 K.However,the data do not satisfy the proposed Simon-Lee scaling law at finite temperatures,i.e.CDOS/(T^2)=fT√H),where f is an unknown scaling function and CDOS is the extra specific heat contributed by the nodal quasiparticles due to the Doppler effect.Possible reasons for this failure are presented.     

Formation of Nanosuized Inclusions in Cubic Boron Nitride Single Crystals

Cubic boron nitride(c-BN) crystals with dimensions of 0.3-0.4mm,which have been synthesized using lithium nitride(Li3N) as a catalyst with a high-temperature method,were examined by transmission electron microscopy(TEM).The TEM result shows that there are some nanostructured areas containing several types of nanosized foreign particles within the as -grown c-BN crystals.We find that the nanometre inclusions are hexagonal BN with the lattice constants of α=2.05A and c=6.66A,tetragonal B25N with α=8.79A and c=5.08A,tetragonal B53N with α=8.79A and c=5.08A,and hexagonal Li3N with α=3.648A and c=3.875A.     

例析两类与菱形有关的动点问题的解决策略

菱形中的动点问题时常出现,是学生学习与菱形有关的知识点的一道关卡.本文中主要介绍两类与菱形有关的动点问题,并以例题分析的形式探讨这两类问题的解决策略.     

Thermoelastic stresses in SiC single crystals grown by the physical vapor transport method

A finite element-based thermoelastic anisotropic stress model for hexagonal silicon carbide polytype is developed for the calculation of thermal stresses in SiC crystals grown by the physical vapor transport method. The composite structure of the growing SiC crystal and graphite lid is considered in the model. The thermal expansion match between the crucible lid and SiC crystal is studied for the first time. The influence of thermal stress on the dislocation density and crystal quality is discussed. The project supported by the National Natural Science Foundation of China (10472126) and the Knowledge Innovation Program of Chinese Academy of Sciences. The English text was polished by Keren Wang