Floating zone growth and magnetic and specific heat properties of La0.67Ca0.33Mn1-xFexO3（x=0.00,0.04）single crystals

Single crystals of La_0.67Ca_0.33MnO₃ and La_0.67Ca_0.33Mn_0.96Fe_0.04O₃ were obtained by floating zone method. Laue diffraction pattern and rocking curve of the single crystals show that their quality is good. The magnetic behaviours of these compounds have been studied. Fe doping significantly depresses the magnetic contribution to the total specific heat C_P, but slightly influences the lattice contribution at temperatures above 50K. The peak of C_P shifts towards high temperatures with increasing magnetic field. Both single crystals exhibit the first-order magnetic transition around the Curie temperature.     

利用压电力显微镜研究PMN-30%PT单晶体中铁电畴的结构及其演变(英文)

本文总结了我们近年来利用压电力显微镜(PFM)研究PMN 30%PT单晶体中铁电畴的结构及其演变的结果。选择PMN-30%PT晶体是因为该组分在超声传感器等应用方面具有最大的潜力。铁电畴的观察是基于反压电现象;具体来讲就是当交变电场通过原子力显微镜探针加到晶体表面时,会引起晶体表面的起伏振荡,而锁相放大器可以解出该振荡信号的振幅和相位角;其中振幅衬度反映了压电系数d_(33)的大小,而相位衬度则反映了铁电畴的极化方向。文中介绍了平面内以及垂直平面的PFM成像技术,并演示了影响畴的图像的一些因素,其中包括静电荷效应,表层效应和机械抛光的影响。本文还利用有限元模型对PFM成像原理进行了模拟分析。着重研究了晶体中铁电畴的尺寸分布,畴与晶体取向,时间和温度的相关性,以及畴的演变过程。     

四硼酸铝钕晶体及其小型全固态激光器

当前,全固态激光器在向万瓦级大功率方向发展的同时,也在向微型化发展。利用碟片全固态激光器可获得千瓦级以上激光,利用微片全固态激光器则可实现小体积、高密度、中小功率激光输出。获得高功率高密度激光的关键在于激光材料。本文从碟片和微片激光器的发展和对激光基质材料的要求出发,概述自激活激光晶体的研究,特别对四硼酸铝钕[NdAl3(BO3)4,简称NAB]晶体的结构、生长、性质及其作为有应用前景的小型片状激光器的候选材料作了详细的介绍。近期,采用面积为4×4 mm2,厚度为0.39 mm的微片NAB晶体,用885 nm半导体激光器为光源泵浦,获得了4.6 W的1.063 μm激光的有效输出,其斜效率达到64%,充分显示了NAB晶体作为自激活激光晶体在微片激光器中的应用前景。     

Synthesis and Crystal Structure of a Ni（Ⅱ） Complex of 2＇-[4-N,N＇-（Dimethylaminobenzyl- idene）]-3,5-dihydroxybenzoylhydrazide and Its Spectral Properties

A new nickel（II） complex [NiL2]（DMF）4 （HL = 2＇-[4-N,N＇-（dimethylamino- benzylidene）]-3,5-dihydroxybenzoylhydrazide） has been synthesized and its structure was characterized by IR,UV-Vis,1H NMR and elemental analysis. The fluorescence emission mechanism of the complex was discussed by fluorimetric spectra. The single-crystal structure was determined by X-ray diffraction analysis. The crystal belongs to the triclinic system,space group P1 with a = 0.9918（4）,b = 1.1297（4）,c = 1.1331（4） nm,α = 76.860（7）,β = 75.105（6）,γ = 89.022（7）°,V = 1.1936（8） nm^3,Z = 1,μ = 0.472 mm^-1,Dc = 1.319 g/cm^3,F（000） = 502 and Rint = 0.0913. In the title compound,the nickel（II） atom is four-coordinated with two nitrogen atoms from amide and two oxygen atoms from keto group. The complex is centrosymmetric with nickel located at the center.     

Raman Spectroscopy and Magnetic Properties of Mn-Doped ZnO Bulk Single Crystal

Mn doped ZnO bulk single crystals are grown by the modified Bridgman method. The as-grown crystals are red in eolour. The additional Raman mode observed at 524cm^-1 is attributed to the Mn ions incorporating into ZnO crystal. The crystal exhibited paramagnetie under lower applied field below 2280 Oe. Then diamagnetism is observed in the crystal when the magnetic field rises up and becomes dominant under applied field above 5270 Oe. The magnetic susceptibility dependence on the temperature follows a Curie law indicating a typical paramagnetie characteristic under an applied field of 2kOe. No ferromagnetic ordering is observed in the as-grown Mn-doped ZnO crystal.     

碳化硅晶须品质及影响因素

采用固相原料，加入适当的催化剂，在保护气氛中反应制备碳化硅晶须，得到的碳化硅晶肌以β晶型为主，兼有少量α晶型，晶须有白色，灰白色，灰绿色，深绿色等多种颜色，其颜色变化与原料中的硅炭比值有直接关系；晶须的光洁度受晶须生长局部范围内过饱和度与保护气氛等因素影响；反应晶料的堆积密度是影响晶须直晶度的主要因素，稻壳原料生长的晶须其直晶率较高。     

钛酸锶单晶体生长工艺研究

使用数控焰熔法晶体生长炉生长钛酸锶单晶体,研究了气体参数、生长速度和退火工艺参数对晶体生长的影响.在氢氧比为2.5,等径生长速度保持在10 mm·h-1,生长出了直径26 mm、等径长度20 mm、总长40 mm的钛酸锶单晶体,然后经过1550℃ ×72 h+1000℃ ×20 h+600℃ ×24 h的退火,消除钛酸锶单晶体的热应力和氧空位,得到完整的高品质的单晶体.偏光显微镜测试表明,晶体具有很好的完整性.     

Crystal Structure of Borophosphate with 6_1 Screw Axis Helices

1 INTRODUCTION Most materials with nonlinear optical pro- perties and electro-optical applications are either borates or phosphates. LBO(LiB3O5), KTP(KtiO- PO4), BBO(b-BaB2O4) and KDP(KH2PO4) are well- known commercially and extensively used for different optical elements. In recent years, the compounds combined both borate and phosphate groups have been synthesized and structurally characterized with quite different anionic partial structures. In particular, the use of hydrot…     

Er~(3+)掺杂Na_5Lu_9F_(32)单晶体的红外光学特性

采用坩埚下降法成功地生长了Er~(3+)离子掺杂的Na_5Lu_9F_(32)(NLF)单晶体。测定了单晶体在400~2 500nm波段的吸收光谱与2.5~25μm红外波段的透过光谱。Na_5Lu_9F_(32)单晶体在400~7 150 nm宽波段范围具有好的光学透过性,在该波段的透过率达到90%。在透过光谱中几乎观察不到2.7μm中红外波段的吸收,说明单晶体中OH~-离子的含量极低。根据测定的吸收光谱,通过Judd-Ofelt理论计算了Er~(3+)在单晶体中的光学强度参数Ω_t(Ω_2=2.08,Ω_4=2.07,Ω_6=0.75),以及相应的辐射跃迁速率、荧光分支比和荧光寿命。根据Futchbauer-Ladenburg公式估算了样品的发射截面大约分别为1.42×10~(-20)cm~2(~4I_(13/2)→~4I_(15/2))和1.66×10~(-20)cm~2(~4I_(11/2)→~4I_(13/2))。在980 nm半导体激光器(LD)激发下,研究了单晶体的近红外1.5μm与中红外2.7μm的发射光谱特性。