Preparation and Characterization of High-Tc YBa2Cu3O7-X Superconductors by Means of Gelation of Metal Dicarboxylate Complexes

The superconductors YBa₂Cu₃C_7-x have been prepared via gelation of metal dicarboxylate complexes. Physical measurements such as XRD, Tc, and X_ac on these ceramics indicate consistently that a better superconducting behaviors were found than that obtained from previously reported oxalate process.     

Superconductivity and crystal structure of the solid solutions of Ba8−δSi46−xGex (0?x?23) with Type I clathrate structure

The solid solutions of barium containing Type I clathrate, Ba_8−δSi_46−xGe_x (0?x?23) were prepared under high-pressure and high-temperature conditions of 3 GPa at 800°C. All the solid solutions showed superconductivity, and the transition temperature (T_c) decreased from 8.0 to 2.0 K as the germanium content increased from x=0 to 23 in Ba_8−δSi_46−xGe_x. The single crystals with five different compositions were obtained and the structures, compositions, and site occupancies were determined from X-ray single-crystal analysis. A slight barium deficiency was observed at Ba1 (2a) sites for all the clathrates. The Ge atoms replaced the Si atoms at the Si3 (24k) site in the composition range of x<8, and then at the Si2 (16i) site. The crystals had a slight deficiency in the covalent (Si, Ge) network and the deficiency increased with the increase of the Ge content.     

Analysis of superconductor oxides YBa2Cu3O8−x by inductively coupled plasma atomic emission spectrometry and complexometric titration

The elemental composition of superconductor oxides YBa₂Cu₃O_8−x were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and complexometric titration. Samples were dissolved in dilute HCl. A sequential PU 7000 Philips inductively coupled plasma atomic emission spectrometer was used for the measurements. A comparison of the different atom and ion emission lines of yttrium, barium and copper was carried out. The effect of changes of forward radio frequency (RF) power coupled into the plasma on emission intensity of various spectral lines was studied. The RF power was changed from 0.8 to 1.2 kW. The changes in the net intensities (%) of the emission lines of Cu(I) at 324.754 nm, Cu(II) at 224.700 nm, Ba(II) at 455.403, Ba(II) at 493.409 nm, Y(II) at 371.030 nm and Y(II) at 360.073 nm were calculated. The indicator 1-(2-Pyridylazo)-2-Naphthol (PAN) and different buffers were used for the complexometric titration of Cu, Y and Ba. No statistically significant differences were found between the results of ICP-AES and chemical methods of analysis.     

Cu-site-substituted REBa2Cu3O7-δ single crystals by top-seeded solution-growth (RE=rare earth element)

Using the top-seeded solution-growth (TSSG) method, Cu-site-substituted REBa₂Cu₃O_7-δ single crystals (REBCO, RE=rare earth elements) were grown. For theoretical studies and practical applications, metal element M (M=Zn, Fe, Ni, Al and Mg) was used for substitution. The optimal processes led to high-quality crystals with sufficient dimension at a high doping level. Thermodynamic and kinetic problems of growing M-doped REBCO crystals are discussed, including the M substitution limit in crystal, the effect of solvent composition on the M substitution in crystal, the crystal growth model of the M-doped REBCO, the phase relation of RE–Cu–M–O systems and composition/property control.     

一维Al/SrF2低温超导体-电介质光子晶体能带结构

基于二流体电子模型和平面波展开法,计算了一维Al/SrF2超导体-电介质光子晶体的能带结构.结果表明:随着超导层厚度的增加,第一光子带隙中心频率和截止频率均发生蓝移,且第一带隙宽度逐渐增加到一个峰值后又逐渐变窄.更重要的是,在低于临界温度的超低温环境中,温度的微小变化,对该类光子晶体的带隙宽度、中心频率以及截止频率均有...     

Nickel-based layered superconductor, LaNiOAs

Rietveld analysis of the powder X-ray diffraction of a new layered oxyarsenide, LaNiOAs, which was synthesized by solid-state reactions, revealed that LaNiOAs belongs to the tetragonal ZrCuSiAs-type structure (P4/nmm) and is composed of alternating stacks of La-O and Ni-As layers. The electrical and magnetic measurements demonstrated that LaNiOAs exhibits a superconducting transition at 2.4 K, and above this, LaNiOAs shows metallic conduction and Pauli paramagnetism. The diamagnetic susceptibility measured at 1.8 K corresponded to ∼20% of perfect diamagnetic susceptibility, substantiating that LaNiOAs is a bulk superconductor.     

ITER CC导体测试装置数据采集系统的设计与应用

系统介绍了ITER CC性能认证超导导体测试装置数据采集系统的硬件设计。该系统可以对温度、压力、流量、液位、电流、磁场、电阻、电压降等物理量进行测量,并能根据实际需要进行系统扩展。另外还对基于VC++6.0编程环境下的数据采集系统的程序设计进行了介绍。通过对软件和硬件的集成调试,该系统实现了高速高精度的数据采集。     

含超导材料Cantor序列一维光子晶体的传输特性

利用传输矩阵法研究了按分形三分Cantor序列构成的一维超导光子晶体的传输特性。数值结果表明,与传统电介质材料构成的光子晶体的频谱不同,这种光子晶体频谱没有展现出自相似性。此外,当构成光子晶体的两种材料的光学厚度相同时,光子晶体的频谱具有明显的周期性,并且在光子带隙中间成对地出现缺陷模。这种特性可以用于设计通道滤波器。     

Tl2Ba2Ca2Cu3O10的化学键性质和同质异能位移研究

在Tl2Ba2Can-1CunO2n 4(n=1,2,3,4)系列超导性氧化物中,Tl2Ba2Ca2Cu3O10具有最高Tc值(125 K)．利用电介质的平均能带模型计算了Tl2Ba2Ca2Cu3O10的局域化学键参数,得到Cu(1)-O键的共价性为0．561,Cu(2)-O键的平均共价性为0．296．应用化学环境因子计算了57Fe在Tl2Ba2Ca2Cu3O10中的穆斯堡尔同质异能位移,证实了57Fe在低掺杂时以Fe3 和Fe4 离子形式占据Cu(1)位置,而在高掺杂时以Fe3 和Fe4 离子形式分别占据Cu(1)和Cu(2)位置．结果表明,化学键理论计算有助于复杂晶体的穆斯堡尔谱的正确分析．     

高温超导磁阻电机的研究

本文针对超导磁阻电机结构并结合临界态模型，利用有限元法计算电机内部磁场和交直轴电抗，借以分析电机稳态工作特性，通过样机构造及其性能测试和分析，证实了HTS磁阻电机较传统电机能够以更小体积和重量实现更大的输出功率、更高的功率因数和效率，此项研究为百kW-MW级HTS磁阻发电／电动机研发奠定了良好的理论和实践基础．