铁磁(La0.7Ca0.3MnO3)/高温超导（YBa2Cu3O7）双层薄膜微结构的高分辨电镜研究

采用脉冲激光沉积法在LaAlO3(LAO)衬底上生长了YBa2Cu3O7/La0.7Ca0.3MnO3(YBCO/LC-MO)和La0.7Ca0.3MnO3/YBa2Cu3O7(LCMO/YBCO)两种外延薄膜,利用高分辨电子显微镜研究了其微观结构。在YBCO/LCMO/LAO薄膜中,LCMO以层-岛模式生长,并形成层状取向畴结构。YBCO层均由c轴取向晶粒组成,其中含有c/3平移畴界、额外CuO层及Y2O3第二相等缺陷结构。在LCMO/YBCO/LAO薄膜中,LAO衬底上初始生长的YBCO为c轴取向,至一定厚度(几个纳米)转为c与a轴混合生长。LCMO层在YBCO上外延生长并具有[100]m与[011]m混合取向畴结构。在LCMO/YBCO界面未观察到失配位错,因此二者界面属应变型界面。     

La0.67Ca0.33MnO3/YBa2Cu4O8/La0.67Ca0.33MnO3三层膜的时间效应研究

报导了La0.67Ca0.33MnO3/YBa2Cu4O8/La0.67Ca0.33MnO3薄膜中超导特性的时间效应.样品在空气中存放11个月后,超导转变温度都降低,而且每个系列样品的临界厚度增加.对用La0.67Ca0.33MnO3作保护层的YBa2Cu4O8薄膜进行时间效应测量,结果表明当La0.67Ca0.33MnO3层的厚度大于40nm时可以防止水对YBa2Cu4O8薄膜的影响.     

Cu—Cr—Zr合金强化机理电子理论研究

通过自编软件建立了Cu合金液体、位错、晶界等原子集团模型，采用递归法计算了Cu合金电子结构。研究表明：Y在晶粒、表面、液体的环境敏感镶嵌能依次降低，Y从晶粒内向晶粒表面、液体Cu中扩散。扩散过程中Y原子填补在Cu晶粒表面缺陷处，阻碍Cu原子结晶，同时进入液体中的Y在晶粒周围形成含有高浓度Y的薄层，使晶粒生长受阻，晶粒细化。Sn向位错扩散，抑制Cr的沉淀析出，并能钉扎位错的攀移运动，推迟回复和再结晶。S在晶界偏析，使晶界结合强度降低。偏聚在晶界的S可将合金中的Zr吸附到晶界，使晶界得到强化。Cu晶粒、晶界与位错处的费米能级不同，电子在这些区域之间发生偏移，使合金内产生微电场。微电场对电子产生散射作用，使合金电阻增大。     

超导PbO/YBa2Cu3O7-δ复合氧化物摩擦磨损性能

为适应从低温到高温宽温范围的使用条件,用溶胶-凝胶法制备了YBa₂Cu₃O_7-δ超导材料,用摩擦磨损试验机测试了YBa₂Cu₃O_7-δ从室温至液氮温度的摩擦学性能。结果表明：室温20℃下,YBa₂Cu₃O_7-δ与对偶件不锈钢盘对摩时,摩擦因数在0.5左右,当温度降到超导转变温度以下时（液氮温度-196℃）摩擦因数大幅度降低,YBa₂Cu₃O_7-δ超导态摩擦因数是正常态值的一半,实验直接证明了电子激励对摩擦能量耗散的作用。为改善室温下YBa₂Cu₃O_7-δ摩擦学性能, 掺杂不同质量分数PbO作为润滑组元,制备了PbO/YBa₂Cu₃O_7-δ超导固体润滑复合材料,取得良好效果。PbO掺杂不影响PbO/YBa₂Cu₃O_7-δ复合材料的超导电性,在正常的载荷和滑行速度下15%PbO/YBa₂Cu₃O_7-δ复合材料摩擦因数为0.2至0.3,磨损率为4.35×10-4 mm3·（N·m）-1,分析了PbO/ YBa₂Cu₃O_7-δ复合材料减摩耐磨机制。     

Synthesis of a YBa2Cu3O7-x-Ag composite using a sol-gel method

The preparation of YBa2Cu3O7-x-Ag powders by a sol-gel method and the characterization of these powders and also pellets made from these powders is presented. Transmission electron microscopy (TEM) observations show that the silver is highly dispersed in the sample. However, the size of the silver particles in the YBa2Cu3O7-x matrix depends largely on the silver concentration in the sample. For low concentrations, the silver particles have sizes of area 10 nm and for higher concentrations the silver particle is larger. The TEM investigations of the powders shows fibre structures for the YBa2Cu3O7-x-Ag composite. This structure is different from the structures usually observed in the YBa2Cu3O7-x system. The microanalysis of these fibres shows that they possess a composition of YBa2Cu3O7-x. The oxygenation of the samples seems easier in YBa2Cu3O7-x-Ag composites. The room temperature electrical resistivity of the pellets is decreased by the addition of silver but no enhancement of the superconducting critical temperature is observed. This revised version was published online in November 2006 with corrections to the Cover Date.     

Realizing the Rapid Crystallization of YBa2Cu3O7-δ Films on LaMnO3 Buffer Layer by Induction Heating

Journal of Superconductivity and Novel Magnetism - YBa2Cu3O7-δ (YBCO) thin films were fabricated rapidly on LaMnO3/MgO/Y2O3/Al2O3/Hastelloy substrate by the self-built induction heating...     

Hole Content Dependent Fluctuation Diamagnetism in YBa2Cu3O7−δ: Possible Role of the Pseudogap

Journal of Superconductivity and Novel Magnetism - This study focuses on the temperature and hole content dependent fluctuation diamagnetism of hole-doped YBa2Cu3O7?δ (Y123) high-Tc...     

A Superconducting Joint for 2G HTS Tapes

Technical Physics Letters - An approach of the epitaxial jointing of the GdBa2Cu3O7 – δ-based tapes using the YBa2Cu3O7 – δ layer is proposed. The structural and electrical...     

前驱体温度对激光化学气相沉积YBa2Cu3O 7δ超导薄膜结构及性能的影响

采用激光化学气相沉积法在Al2O3基底上以49μm·h-1的沉积速率高速制备了c-轴取向的YBa2Cu3O 7-δ薄膜,其中,激光功率为133 W,沉积温度1103 K,腔体压强800 Pa。研究了前驱体蒸发温度及薄膜退火温度对薄膜电学性能的影响。研究表明,Ba、Cu、Y前驱体加热温度分别为603、478、459 K时制备的薄膜在经813 K高温热处理12 h后,临界温度可达83 K。     

Analysis of the spatial distribution of Y2BaCuO5 inclusions in large-grain YBa2Cu3O7-δ

High values of critical current density, Jc, in large-grain superconducting melt-processed YBa2Cu3O7- (YBCO, Y-123) have been reported to correlate closely with the distribution of Y2BaCuO5 (Y-211) particles in the Y-123 phase matrix. Extensive image analysis of the homogeneity of the Y-211 particle distribution in a large-grain sample has been performed on high-resolution, secondary scanning electron micrographs of seeded melt-processed YBCO. The variation of key parameters, such as area fraction, number density and size along the a/b axis of the Y-123 grain has been investigated in detail as a function of distance from the centre of the seed. Both area fraction and number density of Y-211 particles are observed to increase continuously with distance, whereas the mean and standard deviation of the size distribution decrease slightly towards the grain boundary. This suggests that the increase in area fraction can be attributed to an increase in number density of the Y-211 particle distribution along the a/b axis of the specimen. The implications for Y-211 particle pushing, ripening and coalescence are discussed in the light of these results. © 1998 Chapman & Hall