Superconductor Science & Technology
In this paper we report the transport properties of c-axis-oriented superconducting La(1.44)Nd(0.4)Sr(0.16)CuO(4) films on LaSrAlO(4) substrates with different thicknesses in various magnetic fields parallel and perpendicular to the c axis of the films. It is found that with decreasing film thickness there is a crossover from the parallel shift to fan-shape broadening in the resistive transitions. Moreover, for both field configurations, the flux pinning potential U(0)(H) of the film shifts upward with an order of magnitude with increasing in-plane compressive strain. These results indicate that the compressive epitaxial strain and strain-induced destabilization of the static charge stripes are important aspects for the promotion of superconducting transition temperature as well as the flux pinning potential.
关键词:
high-temperature superconductors;crystal thin-films;flux motion;la2-xsrxcuo4;strain;insulator;dependence;behavior
罗军
,
钟真武
,
范世(马豈)
,
王锦昌
人工晶体学报
doi:10.3969/j.issn.1000-985X.2000.01.005
本文首次报道了Ca4YO(BO3)3(YCOB)晶体的坩埚下降法生长.在1600～1650℃炉温下,固液界面处的纵向温度梯度为40～60℃/cm,以0.2～0.6mm/h的生长速率,在近封闭的Pt坩埚中生长出了直径达25mm、长度超过50mm的完整透明YCOB晶体.介绍了生长工艺和原料制备,观察发现晶体中的主要宏观缺陷是包裹体.分析了包裹体生成的原因.
关键词:
布里奇曼法
,
Ca4YO(BO3)3晶体
,
非线性光学材料
,
包裹体
Physica B-Condensed Matter
Nanocapsules consisting of B2O3/H3BO3 encapsulating Fe-Gd cores have been synthesized by an arc-discharge process using metal-boron alloys as cathode. Most of the nanocapsules have a well-constructed shell/core structure with a uniform B2O3/H3BO3 shell. Heat-treatment induces reactions between the shell and the core, resulting in the formation of a Fe3BO5+GdBO3 matrix embedded with Fe nanoparticles, reduction of the metallic-core size and decrease of the blocking temperature T-B. Above T-B, the magnetization curves plotted vs. H/T overlap and show zero coercivity. Below T-B, the coercivity shows a linear dependence when plotted vs. T-1/2. However, the coercivity-T-1/2 curve below 60 K has a different slope from that above 60 K, indicating the existence of two different magnetic phases in the nanocapsules. Different from bulk Fe3BO5, nanoscale Fe3BO5 particles have a lower transition temperature to the weak-ferromagnetic state. and magnetic hysteresis is absent due to size effects. (C) 2004 Elsevier B.V. All rights reserved.
关键词:
nanocapsules;transmission electron microscopy (TEM);X-ray;photoelectron spectroscopy (XPS);magnetic properties;arc-discharge;boric-acid;boron;carbon;oxide;nanoparticles;particles;diborane;iron
张国春
,
傅佩珍
,
李云阁
,
吴以成
人工晶体学报
doi:10.3969/j.issn.1000-985X.2005.05.001
以Na2CO3-H3BO3为助熔剂,用顶部籽晶法生长出Na3La9O3(BO3)8单晶.测定了Na3La9O3(BO3)8晶体结构,结果表明:该晶体属六方晶系,空间群:P62m,晶胞参数为a=b=0.89229(13)nm,c=O.87366(17)nm,α=β=90°,γ=120°,Z=1,V=0.60240(17)nm3,密度为5.066g/cm3.晶体结构中的硼氧基团是平面的BO3基团,BO3基团相互独立,通过与Na(1)O6、La(1)O9和La(2)O8的配位多面体连结形成层状结构,所有层平行于(001)面.描述了Na3La9O3(BO3)8晶体在非线性光学材料领域的应用前景.
关键词:
Na3La9O3(BO3)8
,
晶体结构
,
倍频效应
张国春
,
李云阁
,
傅佩珍
,
潘世烈
,
常峰
,
吴以成
人工晶体学报
doi:10.3969/j.issn.1000-985X.2004.04.007
以Na2CO3-H3BO3-NaF为助熔剂,使用顶部籽晶法生长出Na3La2(BO3)3透明单晶.测定了Na3La2(BO3)3的晶体结构,该晶体属正交晶系,空间群:mm2(No.38),晶胞参数为a＝0.51580(10)nm,b=1.1350(2)nm,c=0.73230(15)nm,α＝β＝γ＝90°,V＝0.42871(15)nm3,密度:.053g/cm3.晶体结构中的硼氧基团是平面的BO3基团,BO3基团相互独立,且与Na(1)O6、Na(2)O8、Na(3)O6和La(1)O9配位多面体连结形成三维网络骨架结构.讨论了Na3La2(BO3)3的晶体结构与倍频效应的关系.
关键词:
Na3La2(BO3)3
,
晶体结构
,
倍频效应
刘剑
人工晶体学报
采用高温溶液法从BaCO3,BaF2及H3BO3混合体系中生长出了一种氟硼酸钡晶体,Ba7(BO3)3F5晶体属六方晶系,空间群为P63mc,晶胞参数:a=1.11562(15) nm,c=0.72415(14) nm,Z=2,V=0.7805(2) nm3.Ba7(BO3)3F5晶体结构是由Ba(1)O7F3基团,Ba(2)O4F3基团,Ba(3)O6F4基团和独立的BO3基团相互连接形成的三维空间网络结构.Ba7(BO3)3F5的热分析分析结果表明Ba7(BO3)3F5在1070℃同成份熔化.
关键词:
Ba7(BO3)3F5
,
晶体结构
,
高温溶液法
余金秋
,
王晓洋
,
罗思扬
,
刘丽娟
,
陈创天
人工晶体学报
通过化学腐蚀和偏光显微镜,对KBe2BO3F2(KBBF)和RbBe2BO3F2 (RBBF)晶体中存在的一种条状孪晶缺陷进行了研究,观察了孪晶习性,探讨了其孪晶律,并结合晶体生长情况对该孪晶的形成原因进行了分析.
关键词:
KBBF
,
RBBF
,
孪晶缺陷
张天真
,
李静
,
王继扬
,
张洋
人工晶体学报
采用助熔剂自发成核法,探索了生长YBaNa(BO3)2晶体的不同助熔剂体系,从中选出2Na2CO3-4H3BO3-BaCO3做助熔剂,生长了YBaNa(BO3)2晶体.采用X射线衍射(XRD),红外吸收光谱和透过光谱,差热失重分析对生长的晶体进行了表征.结果表明,晶体属于六方晶系,空间群为R3,晶胞参数为a=0.53382(2) nm,c=3.58303(19) nm.BO3-3基团存在于晶体结构中,晶体的紫外截止波长在208 nm左右,晶体在800℃时有明显的相变点.
关键词:
自发成核
,
助熔剂
,
YBaNa(BO3)2晶体
