X-ray study of the reentrant modulated phase of Bis-Propylammonium Tetrachlorocuprate(II) at high temperature

The modulated phase of (C₃H₇NH₃)CuCl₄ stable between 386 and 412 K has been analyzed by single-crystal X-ray diffraction. The structure was solved in the frame of the superspace group approach. The modulation is characterized by a wavelike displacement of the CuCl₄ layer.     

Low-temperature growth of high-Tc superconducting films by plasma-enhanced metal-organic chemical vapor deposition

Plasma-enhanced MOCVD in which metal-organic compounds are sublimated directly into the growth chamber is studied for the first time as a new low-temperature process for growing superconducting YBa₂Cu₃O-_-x thin films. Y(THD)₃, Ba(THD)₂, Cu(THD)₂ and oxygen are used as metal sources and oxydizing agent. Emission spectroscopy reveals that activated metal-organic compounds and activated oxygen species are present during film growth. Superconducting YBa₂Cu₃O_7-x films whose zero-resistivity temperature are 50 K and 82 K are grown at 550°C and 600°C.     

Zr掺杂对MgB2超导微观结构和超导电性的影响

将Mg粉、Zr粉和B粉按比例混合获得Mg1-xZrxB2(x=5%10%和20%),压制成型后,在流通氩气的条件下于800℃烧结2h.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)分析烧结后样品的显微结构和化学组成,采用差热分析(DTA)观察Zr掺杂对MgB2分解温度的影响,并用物性测试仪(PPMS)测试样品的超...     

Study of nano-sized (ZnFe2O4)y particles/CuTl-1223 superconductor composites

Zinc ferrite (ZnFe₂O₄)_y nanoparticles/Cu_0.5Tl_0.5Ba₂Ca₂Cu₃O_10−δ (CuTl-1223) superconductor composites with y = 0–2 wt.% were prepared by adding ZnFe₂O₄ nanoparticles into CuTl-1223 superconductor matrix and characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transforms infrared (FTIR) spectroscopy and dc-resistivity (ρ) measurements. The bulk CuTl-1223 superconductor matrix was synthesized by solid-state reaction and Zinc ferrite (ZnFe₂O₄) nanoparticles were separately prepared by sol–gel method. XRD analysis revealed the tetragonal and spinel structure of CuTl-1223 superconductor and ZnFe₂O₄ nanoparticles, respectively. The XRD analysis showed that increased concentration of ZnFe₂O₄ nanoparticles doesn't disturb the tetragonal structure of host CuTl-1223 superconductor matrix and has no appreciable effect on its lattice parameters. The SEM images confirm the granular structure of the host superconductor matrix. The presence of ZnFe₂O₄ nanoparticles in host superconductor matrix is confirmed by using FTIR study. Variation of zero resistivity critical temperature {T_c (0)} depends upon the concentration of the nanoparticles in the host superconductor matrix. The overall suppression of T_c (0) and diamagnetism with increasing nanoparticles concentration is most probably due to trapping of mobile free carriers and reflection of spin charge due to presence of paramagnetic ZnFe₂O₄ nanoparticles. There is possibility for the incorporation of Fe and Zn in the lattice sites during the synthesis process, which may also cause the reduction of T_c (0) of the final composites.     

高温超导体中磁通涡旋薄饼运动的实验证明

为了验证高温超导体中涡旋薄饼运动的存在,我们设计了电流和电位引线分处样品不同表面的实验。实验结果表明,在这种电流电位引线配置下的E～j关系不同于刚性涡旋线运动所预期的E～j关系,由此支持了涡旋薄饼运动的存在。     

高温超导体磁通跳跃数值模拟

文中基于超导磁通动力学理论,考虑电磁力与热激活对磁通运动的影响,基本物理模型由等效电阻率随超导体温度和磁场变化的磁通扩散方程,以及比热随超导体温度变化的热传导方程组成。在此基础上,用差分法数值求解了这一复杂非线性系统的磁热耦合控制方程,得到了与实验观测结果基本一致的数值模拟结果。结果还表明：外加磁场变化速度、超导体初始温度以及超导尺寸对于磁通跳跃均产生明显的影响。     

稀土在中国高新材料研制开发中的应用

我国在稀土资源和稀土原料的生产方面都居世界领先地位，近年来稀土高新材料的研制与开发也取得重大进展。本文概述了我国在稀土高新材料开发与研究方面的成果，指出今后应把稀土应用基础研究、中重稀土的应用研究和稀土在能源领域的应用研究作为重点进一步开展工作。     

The decomposition of the oxalate precursor and the stability and reduction of the YBa2Cu4O8 superconductor studied by TG coupled with FTIR and by XRD

The 124 superconductor YBa₂Cu₄O₈ was prepared from the oxalate precursor Y₂(C₂O₄)₃. ·4BaC₂O₄·8CuC₂O₄·xH₂O at one atmosphere oxygen pressure. In O₂ the precursor decomposes in one step at 300°C and more gradually (300°–600°C) in Ar. The stability of the superconductor is strongly dependent on the gas atmosphere: in O₂ and in air there is no significant weight change as long as the temperature does not exceed 800°C, whereas in a 1% O₂-99%N₂ mixture decomposition starts at about 670°C with the formation of CuO and YBa₂Cu₃O_x withx<7. The reduction of YBa₂Cu₄O₈ in a 5% H₂-95% Ar mixture takes place in at least four major steps with formation of products such as Y₂O₃, BaO, Cu₂O, Cu, BaY₂O₄ and Ba₄Y₂O₇.     

Studies of heterogeneity properties of selected high-temperature superconductor surfaces

Nitrogen adsorption measured at 77 K was used to characterize the surface heterogeneity of high-temperature superconductor surfaces. Properties relating to adsorption and porosity of the solids (adsorption capacity, specific surface area, radii and volume of the pores, pore-size distribution function) were determined from nitrogen adsorption–desorption isotherms and atomic force microscopy (AFM) for a series of oxide superconductors. It is shown that the adsorption isotherms of all samples are S-shaped and belong to type II according to the IUPAC classification. On the basis of the nitrogen adsorption isotherms and AFM data, fractal dimensions were determined and correlations found with adsorption and porosity parameters.     

超导电力技术新进展及其未来发展的思考

近年来高温超导材料研究取得很大进展,它在电力领域的应用研究已受到广泛关注,一些示范样机,诸如高温超导输电电缆、变压器、故障电流限制器、电机和储能装置已经研制成功并投入示范性试验.超导技术是21世纪具有战略经济意义的高新技术,文章将介绍高温超导电力应用研究的新进展及其未来发展的思考。