氧在yBa2Cu3O6向yBa2Cu3O7转变中的活度

本文在作者的 YBa_2Cu_3O_6+(1/2)O_2(?)YBa_2Cu_3O_7可逆转变模型的基础上,提出了氧在如上反应过程中的活度概念,并讨论了可逆转变反应的标准自由焓和活度系数.     

Pinning potential in thick PrBa2Cu3Ox/YBa2Cu3O7−δ quasi-multilayers

Using Pulsed Laser Deposition we have fabricated thick quasi-multilayers composed of incomplete layers of PrBa₂Cu₃O_x (PrBCO) nano-dots and layers of YBa₂Cu₃O_7?δ (YBCO). The number of such sequences was between 2 and 6, with the thickness of individual YBCO layers between 565 and 885 nm, and total thickness between 1.13 and 5.31 μm. For the thinner quasi-multilayer, DC magnetization studies showed an increase in the critical current density J_c at all fields in comparison with a pure YBCO reference sample, while the thicker samples showed an increased J_c only in high fields. We have also investigated the frequency dependence of J_c from AC susceptibility studies and found that the pinning potential is well described by a logarithmic dependence on current density. Pinning potentials in PrBCO/YBCO quasi-multilayers also proved to be higher than in the reference sample at high fields. From angle-dependent transport measurements we have found indications of strong pinning centres induced by the (PrBCO) nano-dots, both isotropic and c-axis correlated.     

YBa2Cu3O7纳米桥rfSQUID

我们采用电子束曝光和氩离子刻蚀技术制备了ＹＢＣ纳米桥，在此基础上得到高温ｒｆＳＱＵＩＤ，器件的磁通噪声为４×１０＾－４Φ／√Ｈｚ，磁场分辨率为２．０ｐＴ／√Ｈｚ，对没有三角波的器件，经过ＥＤＴＡ后腐蚀技术对纳米进行弱化处理，部分器件出现了三角波。     

Metallization of Cu3N Semiconductor under High Pressure

Using the four-probe method, we investigate the electrical conductivity of Cu3N under high pressure with the diamond anvil cell. Cu3N is a semiconductor at ambient pressure showing a band gap about l eV. With the application of quasi-hydrostatic pressures, its resistance decreases dramatically over five orders of magnitude from ambient to 9 GPa. The compound became a metal at pressure about 5.5 GPa, which is in well agreement with the recent first principle calculation.     

纳米Cu3 N薄膜的制备与性能

采用柱状靶多弧直流磁控溅射法,100℃基底温度下在玻璃衬底上制备了纳米氮化铜(Cu3N)薄膜.用x射线衍射研究了不同氮气分压对Cu3N薄膜晶体结构及晶粒尺寸的影响.结果显示薄膜由Cu3N和Cu的纳米微晶复合而成,其中Cu3N纳米微晶具有立方反ReO3结构.通过原子力显微镜对薄膜表征显示,膜表面比较光滑,具有较低的粗糙度.x射线光电子能谱对薄膜表面的成分分析表明,Cu3N薄膜表面铜元素同时以+1价和+2价存在.Cu3N的Cu2p3/2,Cu2p1/2及Nls峰分别位于932.7,952.7和399.9 eV,Cu2p原子自旋-轨道耦合裂分能量间距为20eV.用台阶仪和四探针方法测量了薄膜的厚度及电阻率,薄膜的沉积速率和电阻率在很大程度上受到氮气分压的调制.     

YBa2Cu3Ox高温超导涂层的研制

本文叙述了用氢-氧焰喷涂法研制 YBa_2Cu_3Ox 高温超导带的技术,并通过对超导涂层及各种基材间所形成的界面分析指出,在超导带研制中基底材料与涂层间的相互扩散;基底材料抗高温氧化特性,诸如氧化速度、氧化层粘合度等均为高温超导带研制中的某些关键问题.     

团簇WOS3Cu3I(2-MePy)3激发态非线性光学性质

用Z扫描方法测量了团簇WOS3Cu3I(2 MePy) 3对 5 32nm、8ns激光脉冲的非线性光学响应曲线。以速率方程为基础对实验结果进行拟合 ,理论计算和实验结果符合得很好。应用激发态折射理论研究了非线性折射率系数的符号变化和折射度比值Kr 的关系 ,Kr>1时非线性折射率系数为正 ,Kr<1时折射率系数为负。     

低激光能流沉积高质量的NdB2Cu3O7-x/YBa2Cu3O7-y高温超导薄膜

采用脉冲激光方法,先在YSZ（yttria stablized zirconia)衬底上制备（YBa2Cu3O7-y)/YSZ高温超导薄膜,再用较低的激光能流密度（1.2-1.0Jcm^-2)沉积一层NBCO（NdB2Cu3O7-x)薄膜,形成NBCO／YBCO／YSZ双层超导薄膜。在制备完当时,存放40天和存放400天后分别对薄膜进行了X射线衍射分析和电阻－温度曲线测量。结果表明,NBCO／YBCO／YSZ双层膜的转变温度、结晶度和表面稳定性及光滑度都优于YBCO／YSZ薄膜的。在YBCO／YSZ上使用较低的激光能量可以制备出优质的c轴取向NBCO高温超导薄膜。     

Magnetostriction of REBa2Cu3O7-δ

The magnetostriction (MS) of REBa₂Cu₃O_7– (RE=Y, Nd, Eu, Gd, Ho, Er, Yb) is reported as a function of magnetic field and temperature forH<5 T and 1.5H>1 T. The MS is much larger when the rare earth carries a magnetic moment, as usual, but the volume MS observed with moment carrying REBa₂Cu₃O_7– is larger than that of nonsuperconducting intermetalics. This effect is explained by the shielding currents which are induced by the 4f magnetic moments in the superconducting CuO-lattice. The thermal expansion of GdBa₂Cu₃O_7– shows a large peak at the ordering temperature of 2.2 K in both the superconducting and the nonsuperconducting samples.     

Y稳定的ZrO2基体上YBa2Cu3O7／SrTiO3／YBa2Cu3O7异质外延三层…

采用磁控溅射方法在（１００）ＹＳＺ基底上沉积了ＹＢａ２Ｃｕ３Ｏ７／ＳｒＴｉＯ３／ＹＢａ２Ｃｕ３Ｏ７异质外延三层膜。利用交流磁化率和四引线电阻测量的方法确定了三层膜的超导性能，利用Ｘ射线衍射和透射电子显微镜研究了三层膜的结构特征。研究结果表明，膜层的结晶质量较好，临界转变温度Ｔｃ在８３．５Ｋ和８６．７Ｋ之间。ＹＢＣＯ膜层中的绝大多数甚至全部）晶粒为ｃ取向，在有些膜中只存在少量的ａ或ｂ取向的ＹＢＣＯ晶     

YBa2Cu3O7—x和GdBa2Cu3O7—x薄膜中的涡旋玻璃转变的观察

本给出了具有高密度孪晶界ｃ取向ＹＢａ２Ｃｕ３Ｏ７－ｘ外延薄膜存在涡旋玻璃转变及很好的标度行为的实验证据，在有ａ方向昌粒或４５°晶界的ＧｄＢａ２Ｃｕ３Ｏ７－ｘ外延薄膜中存在涡旋玻璃转变但在转变温度附近观察到磁通蠕动和热激活磁通流的某些特征。     

Ag／YB12Cu3O7—x,Al／YBa2Cu3O7—x界面特性分析

利用电学测量方法结合二次离子质谱（ＳＩＭＳ）技术对金属Ａｇ与Ａｌ与ＹＢａ２Ｃｕ３Ｏ７－ｘ（ＹＢＣＯ）超导薄膜接触界面电学性质和扩散特征进行了测试分析，分析结果显示由于Ａｇ和Ａｌ具有不同的化学性质，二与ＹＢＣＯ界面的互扩散特性有明显不同，这些不同影响到接触界面的电学性质和接触窗口下ＹＢＣＯ超导性能，在Ａｇ／ＹＢＣＯ样品中，在高于３５０℃以上的温度下氧气氛中退火将引起Ａｇ和Ｏ的界面互扩散，但对ＹＢＣ     

YBa2Cu3O7—δ中Cu—O伸缩振动的红外吸收峰

测量了ｃ轴高度定向的ＹＢａ２Ｃｕ３Ｏ７－δ高Ｔｃ超导薄膜经３００～７５０℃退火后的红外反射光谱和不同掺Ｚｎ量的ＹＢａ２Ｃｕ３－ｘＺｎｘＯ７－δ块状材料的红外吸收光谱。根据这些光谱中Ｃｕ－Ｏ吸收峰的变化，证实了在ＹＢａ２Ｃｕ３Ｏ７－δ体系的红外光谱中，６３０ｃｍ＾－１、５９０ｃｍ＾－１、和５５０ｃｍ＾－１三个吸收峰分别对应的Ｃｕ－Ｏ伸缩振动膜，以及与氧缺位的关系。并讨论了二维电子气屏蔽对吸收峰的影响     

YBa2Cu3O7—δ中Cu—O伸缩振动的红外吸收峰

根据YBa_2Cu_3O_(7-δ)超导定向膜经不同温度退火后的红外反射光谱和不同掺Zn量的YBa_2Cu_(3-z)Zn_xO_(7-δ)的红外吸收光谱在500-700厘米~(-1)特征峰的变化,进一步讨论了YBa_2Cu_3O_(7-δ)中Ba-Ba层间和Y-Ba层间Cu-O键伸缩振动的三个红外吸收峰强度变化的本质。用红外入射光穿透深度随Y系样品电阻率提高而增大和对应二维CuO_2网络中Cu-O反称振动吸收的590厘米~(-1)峰强度变化不受氧缺位影响的事实,说明590厘米~(-1)的吸收峰不是氧缺位诱导的准局域振动模。同时对620厘米~(-1)和550厘米~(-1)吸收峰的解释也给予了必要的补充和验证。     

Local electronic structure of Cu2O,CuO and YBa2Cu3O7−δ

Cu 3d and O 2p electronic states of Cu₂O, CuO, and the highT _c compound YBa₂Cu₃O_7– have been probed by means of high resolution x-ray emission spectroscopy (XES). The CuL and OK XES bands are compared in detail with recently reported x-ray photoelectron and ultraviolet photoelectron spectroscopy (XPS and UPS) measurements and densities of states obtained by local density functional (LDF) theory. The XES data show that the hybridization between Cu 3d and O 2p states is completely modified in CuO and YBa₂Cu₃O_7–, whered-d correlation energy is large, as compared to LDF predictions. Such is not the case for Cu₂O where agreement between theory and experiment is good.The Cu 3d states are found to be highly localized in YBa₂Cu₃O_7– (though less so than in CuO). The O 2p states lie at lower binding energies than in the simpler oxides and are mainly situated above the Cu 3d states. The respective positions of the centre of gravity of the OK emission bands on an x-ray energy scale indicate that the oxygen sites are less well screened by the O 2p states in the highT _c compound. This provides indirect evidence for the presence ofd-like states at the oxygen sites.