X射线荧光基本参数法测定Y_(1-x)Ce_xBa_2Cu_3O_y中的钇铈钡铜

本文用Ｘ射线荧光光谱基本参数法测定了Ｙ１－ｘＣｅｘＢａ２Ｃｕ３Ｏｙ系列样品中的钇铈钡铜含量，然后折算成它们的原子比，测量的结果与ＩＣＰ的结果接近。为非破坏地测定高温超导体的实际组分进行了一次尝试。     

YBa2Cu3Oy超导体中磁通运动的性质

在液氮温区测量了 YBa_2Cu_3O_y 超导体在弱施加磁场中的磁化曲线.发现初始磁化曲线在数十高斯的磁场区出现斜率不等的两段直线.我们认为这是在颗粒结构样品中磁通在两类空间区域中运动,因而也存在两类大小不同的钉扎作用的表现.一类是颗粒边界区,这里钉扎作用较弱,磁通运动较易.另一类是颗粒内部,这里钉扎较强.对颗粒的高分辨率电镜观察表明,颗粒表面层的原子是无序的,颗粒内部的结晶区有大量的微孪晶界存在.这些结果支持以上解释.     

插入二氧化铈薄膜提高MOD-YBa2Cu3O7-x厚膜超导性能的研究

YBa₂Cu₃O_7-x(YBCO)膜存在“厚度效应”: 随着厚度增加, YBCO薄膜的临界电流密度下降, 尤其是YBCO薄膜的厚度超过1 μm时, 它的临界电流密度急剧下降. 本文在YBCO薄膜之间引入极薄的二氧化铈(CeO₂)薄膜, 成功制备出结构为YBCO/YBCO/CeO₂/YBCO的超导厚膜. 所制备的厚度为2 μm的YBCO膜临界电流密度为1.36 MA/cm² (77 K, 自场), 其性能比相同厚度的纯YBCO膜有了较大幅度的提升. 研究表明CeO₂薄膜起到了传递织构、松弛应力的作用.     

用AFM对Y1Ba2Cu3O7-δ微桥局部改性研究

用AFM对高温超导Y1Ba2Cu3O7-δ薄膜微桥进行局部改性，形成非超导的微区。对形成的SNS结构测量了I-V曲线。个别样品发现其I-V曲线对微波辐照异常灵敏。     

Y1—xPrxBa2Cu3Oy中与铁弹性有关的能量损耗的研究

本用拉伸实验的方法，在室温至７８Ｋ的温度范围内，研究了Ｙ１－ｘＰｒｘＢａ２Ｃｕ３Ｏｙ（ｘ分别为０，０．１，０．３，０．４和０．６）的铁弹性行为。结果表明，Ｔｃ以上几十度温度范度内与铁弹性行为有关的能量损耗分析（△Ｗ／Ｗ）以及类似于热弹性马氏体含量的形状记忆效应与类相变有关，并与超导电性有内在的联系。     

Micro—structural analysis of YBa2Cu3O7—x thin films grown on different substrates by X—ray techniques

YBa2Cu3Ox(YBCO) thin films grown on different substrates with and/or without Eu2CuO4(ECO) buffer layer were investigated by X-ray wide angle diffraction,reflection,diffuse scattering and topography.Theresults show that for the yttria stabilized ZrO2(YSZ) substrate,the presence of an ECO buffer layer improves the crystalline quality of the YBCO film,while a negative effect is observed for the SrTiO3(STO) substrate.The lateral correlation length for a sample grown on a YSZ substrate with ECO buffer Layer is much greater than grown on an STO subetrate.The STO substrate used has mosaic structure.2001 Elsevier Science B.V.All rights reserved.     

The superconductive properties and crystal structure of Ba2(Y1−x Pr x )Cu3O9−y solid solutions

A series of Ba₂(Y_1–x Pr _x )Cu₃O_9–y solid solutions were prepared with the orthorhombic distorted perovskite structure. The compound Ba₂PrCu₃O_9–y belonging to tetragonal system is a good semiconductor. The superconductivity is observed for samples withx<0.6. With the increase of Y content, the distortion of crystal structure is greater and the superconductive transition temperature of zero resistanceTc(0) raises.     

Structure of the heavy electron compounds Ce(Cu x Al1-x )5 and Ce(Cu x Ga1-x )5, [0.6≦x≦0.8]

Neutron powder diffraction measurtements on the recently discovered heavy electron compounds Ce(Cu _x Al_1-x )₅ and Ce(Cu _x Ga_1-x )₅ show that Al or Ga atoms in these compounds locate exclusively on the 3g sites of space groupP6/mmm. Further Rietveld analysis shows that these atoms on the 3g sites are disordered.     

铽掺钇配合物[(TbxY1-x)(HL)L'Cl·1/2H2O]的合成及荧光性质研究

以1,3,5-苯三甲酸根(BTC3-)为阴离子配体,1,10邻菲啰啉(phen)为中性配体,以不同摩尔比铽、钇离子为中心体,合成了系列铽掺钇配合物.经C,N,H元素分析,稀土总量络合滴定和铽、钇分量的测定推测配合物的组成为(TbxY1-x)(HL)L'C1·1/2H2O(x=0.10,0.30,0.50,0.70,0....     

Temperature-dependent structures of proton-conducting Ba(Zr(0.8-x)Ce(x)Y(0.2))O(2.9) ceramics by Raman scattering and x-ray diffraction

In situ temperature-dependent micro-Raman scattering and x-ray diffraction have been performed to study atomic vibration, lattice parameter and structural transition of proton-conducting Ba(Zr(0.8-x)Ce(x)Y(0.2))O(2.9) (BZCY) ceramics (x = 0.0-0.8) synthesized by the glycine-nitrate combustion process. The Raman vibrations have been identified and their frequencies increase with decreasing x as the heavier Ce(4+) ions are replaced by Zr(4+) ions. The main Raman vibrations of Ba(Ce(0.8)Y (0.2))O(2.9) appear near 305, 332, 352, 440 and 635 cm(-1). The X-O ( X=Ce, Zr, Y) stretching modes are sensitive to the variation of Ce/Zr ratio. A rhombohedral-cubic structural transition was observed for x = 0.5-0.8, in which the transition shifts toward higher temperature as cerium increases, except for Ba(Ce(0.8)Y(0.2))O(2.9). A minor monoclinic phase possibly coexists in the rhombohedral matrix for x = 0.5-0.8. The lower-cerium BZCYs (x = 0.0-0.4) ceramics do not exhibit any transition in the region of 20-900?°C, indicating a cubic phase at and above room temperature.     

Effect of pressure on the electrical resistivity and thermoelectric power of the compounds Ba(Pb1-xBi x )O3 and K y Ba1-yPb0.5Cu0.5O3-x

High pressure studies on the electrical resistivity and thermoelectric power of BaPb_1-xBi _x O₃ and K _y Ba_1-yPb_0.5Cu_0.5O_3-x show that many compounds in these systems exhibit qualitatively the same type of behaviour as observed in the superconducting oxides (La, Sr)CuO₄ and YBa₂Cu₃O_7-x. The compounds K _y Ba_1-yPb_0.5Cu_0.5O_3-x show temperature-independent resistivity over a wide range of temperatures, but are not found to be superconducting down to 77 K.     

Oxidation states of Cu,Ba and Y in superconducting YBa2Cu3O7−x

A high temperature (91.2 K) Y–Ba–Cu–O superconductor has been studied by monochromatized XPS core level measurements. The position, shape and satellite emission of Cu 2p indicate a mixture of Cu valencies 2+ and 1+ with some indication for the existence of a third oxidation state of 3+. The two component structure of the Ba 3d line suggests two principal Ba–O configurations due to oxygen vacancies. The shape and position of the Y 3d doublet imply only weak Y–O interactions.     

Andreev reflections on Y(1-x)Ca(x)Ba(2)Cu(3)O(7-delta): evidence for an unusual proximity effect

We have measured Andreev reflections between an Au tip and Y(1-x)Ca(x)Ba(2)Cu(3)O(7-delta) thin films in the in-plane orientation. The conductance spectra are best fitted with a pair potential having the d(x2-y2)+is symmetry. We find that the amplitude of the is component is enhanced as the contact transparency is increased. This is an indication for an unusual proximity effect that modifies the pair potential in the superconductor near the surface with the normal metal.