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利用XRD对系列样品YBa2-xMgxCu3O7-δ的晶体结构进行研究,给出了体系相结构的掺杂效应,结果发现,随着掺杂量的增加(x=0～0.2),样品的晶体结构由正交相向四方相转变.同时采用四引线法对掺杂样品YBa2-xMgxCu3O7-δ的超导电性能进行了系统测量,结果表明随着Mg掺杂量的增加超导转变温度总体呈明显降低趋势.初步分析了Ba位Mg掺杂所引起的晶体结构变化对超导电性的影响.该研究结果为高温超导机理的进一步研究提供了实验资料. 相似文献
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采用四引线法对掺杂样品YBa2-xMgxCu3O7-δ和YBa2-xSrxCu3O7-δ(x=0.0～0.2)的超导电性能进行了系统测量,发现随着镁和锶掺杂量的增加,样品的超导转变温度总体呈明显降低趋势.同时利用XRD对系列样品YBa2-xMgxCu3O7-δ和YBa2-xSrxCu3O7-δ的晶体结构进行研究,发现随着掺杂量的增加,样品的晶体结构由正交相向四方相转变.初步分析了钡位镁和锶掺杂所引起的晶体结构变化对超导电性的影响.该研究结果为高温超导机理的进一步研究提供了实验资料. 相似文献
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Floating-zone growth and property characterizations of high-quality La2-хSrхCuO4 superconductor crystals 
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下载免费PDF全文 We have grown underdoped(x=0.11,0.12) and optimally doped(x=0.16) La2 x SrxCuO4 single crystals by the traveling-solvent floating-zone technique.In order to prepare good quality cuprate crystals,we have made much effort to optimize the preparation procedures.For example,we haveadopted the sol-gel route to prepare a highly fine and homogeneous La2xSrxCuO4 precursor powder for fabricating a very dense ceramic feed rod used for the floating-zone growth,and we have also used quite a slow growth rate.The high quality of the grown crystals has been verified by double-crystal x-ray rocking curves,with the full-width-at-half-maximum being only 113-150 arcseconds,which are the best data reported so far for La2xSrxCuO4 crystals.The superconducting critical temperatures of the grown crystals are 30,31 and 38.5 K for x=0.11,0.12 and 0.16 samples,respectively,according to magnetic measurements. 相似文献
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新型超导材料一直是人类追求的目标。该文主要从超导材料的探索与发现、制备技术、基础研究面临的挑战等几个方面来探讨超导材料的发展与研究现状。 相似文献
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Rongwei Hu Sheng Ran Warren E. Straszheim Sergey L. Bud'ko Paul C. Canfield 《哲学杂志》2013,93(24):3113-3120
We report the single crystal growth of Ca(Fe1?x Co x )2As2 (0?≤?x?≤?0.082) from Sn flux. The temperature–composition phase diagram is mapped out based on the magnetic susceptibility and electrical transport measurements. The phase diagram of Ca(Fe1?x Co x )2As2 is qualitatively different from those of Sr and Ba; this could be due to both the charge doping and structural tuning effects associated with Co substitution. 相似文献
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本文报道了对Y1-xRxBa2Cu3O7-δ（R=Eu、Gd）两个系列样品的超导电性研究结果．首先，发现随着Eu、Gd掺杂量x的增加，Y1-x]EuxBa2Cu3O7-δ和Y1-xGdxBa2Cu3O7-δ的晶胞体积均随之增大．但所有样品均保持与Y-123样品相同的单相正交结构；正电子平均寿命实验结果表明Cu—O链处局域电子密度ne随Eu、Gd掺杂浓度x的增加而减小．说明Eu、Gd对Y位的替代引起晶胞结构参量的变化不汉改变了Y位的电子密度．同时也影响了Cu-O链周围的电子密度分布；超导转变温度Tc随Eu、Gd掺杂浓度x增加而略有增加，反映了Eu、Gd掺杂虽然改变了体系的局域电子结构．但没有破坏超导所需的Cu-O链与CuO2面之间的耦合：Y位掺杂体系的超导电性与掺杂离子的磁性无关，而与掺杂离子的半径有关． 相似文献
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Superconductivities and structural properties of Ti-Zr-Ta ternary alloys are extensively investigated. The TiZrTa sample has a cubic structure (β -phase) and shows a sharp superconducting transition at a critical temperature (Tc) of about 7.3 K. In addition, two series of Ti-Zr-Ta alloys, with nominal compositions of Ti65-xZr35Tax and TixZr65-xTa35 respectively, are prepared, and their superconductivities and crystal structures change regularly with the chemical composition. Our experimental study also indicates that the annealing processing of this kind of material can cause the transition temperature to increase and the highest Tc is observed to be about 8.3 K in annealed samples. 相似文献
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富氢化合物在目前实验所能达到的压力范围内有望实现金属化,是潜在的具有高超导临界温度的材料。实验和理论研究均发现高压下S-H化合物的超导临界温度高达203 K,创造了高温超导的新纪录,掀起了新一轮富氢化合物超导电性研究的热潮。本文主要介绍近年来关于氧族氢化物的压致金属化和奇异超导电性研究,对比分析氧族富氢化合物高压行为的异同。氧族元素的最外层电子排布相同,但原子质量和电负性的差异巨大,导致形成的富氢化合物在化学配比、结构、化学成键以及超导电性来源上存在较大差别。S-H和Se-H化合物的超导电性主要源自与氢原子拉伸振动模式相关的强电子-声子耦合,而Te-H和Po-H化合物中对超导电性贡献最大的是氢原子的切向振动模式。 相似文献
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G. Schierning R. Theissmann M. Acet M. Hoelzel J. Gruendmayer J. Zweck 《physica status solidi (a)》2010,207(8):1918-1921
By low‐temperature transmission electron microscopy we have found nanodomains in a polycrystalline Nb3Sn sample. We interpret that these nanodomains form due to a tetragonal distortion. Because twinning seems to be a prominent feature of the real structure of many high Tc superconductors, possible interactions between a twinned structure and superconductivity are briefly discussed. 相似文献
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本文研究了La2Cu1-xVxOv+δ(0≤x≤0.08)的结构及电输运性质.用Rietveld方法对所有样品的X射线衍射谱进行了拟合.结果表明,全部样品都具有正交对称性,晶胞参数随掺杂量的增加几乎没有变化.随着V掺杂量增加到0.08,而La2Cu1-xVxO4+δ中过量氧的平均值从0.006增加到0.007.没有掺杂的样品由于氧过量而存在相分离状态,体系中存在超导相与绝缘相的竞争相互作用.随着V掺杂量增加,超导相受到破坏,我们认为,V掺杂对超导电性抑制的原因可能是载流子浓度的减少和载流子的局域化所致. 相似文献
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Wen-Ji Shen 《中国物理 B》2022,31(7):76102-076102
Solid H$_{2}$S as the precursor for H$_{3}$S with incredible superconducting properties under high pressure, has recently attracted extensive attention. Here in this work, we propose two new phases of H$_{2}$S with $P$4$_{2}/n$ and $I$4$_{1}/a$ lattice symmetries in a pressure range of 0 GPa-30 GPa through first-principles structural searches, which complement the phase transition sequence. Further an $ab initio$ molecular dynamics simulation confirms that the molecular phase $P2/c$ of H$_{2}$S is gradually dissociated with the pressure increasing and reconstructs into a new $P$2$_{1}/m$ structure at 160 GPa, exhibiting the superconductivity with $T_{rm c}$ of 82.5 K. Our results may provide a guidance for the theoretical study of low-temperature superconducting phase of H$_{2}$S. 相似文献
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超导-介质型Fibonacci光子晶体的透射谱与滤波特性分析 总被引：1，自引：0，他引：1
目前广泛应用的可调谐光滤波器通过调节干涉腔长度来实现波段的调谐。它需要制备高反射悬浮膜,而悬浮膜在驱动电压的影响下其运动会受到限制,且较窄的透射峰与较大的调谐范围二者不可兼得。为此,本文将光子晶体中的其中一种介质以超导材料取而代之。基于超导理论,利用传输矩阵法对一维超导-介质型Fibonacci光子晶体的透射谱进行了计算,讨论了厚度、折射率以及温度对透射谱的影响。结果表明,受光子带隙的影响,超导体的频率禁带中会出现一系列的通带;Fibonacci等级的增加会导致第一透射峰更加尖锐;介质层光学厚度增大、超导层厚度减小、温度升高均能使透射峰向长波方向移动。最后,在透射谱分析的基础上给出了结构为S11(S5)n的滤波特性,兼顾透射峰半高宽与可调谐范围,确定了滤波器的可调谐波段,在无需调整任何几何参数的条件下实现了温控调谐。 相似文献
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最近几年,镍基氧化物超导材料方面的研究进展吸引了广大科研工作者的密切关注,其原因是镍基超导的母体RNiO2(R为稀土元素)与铜氧化物高温超导母体之一CaCuO2具有相似的晶体结构,而且其最外层轨道电子排布(3d9)与众多的铜氧化物超导体的母体相似。因此,对相关镍氧化物进行深入的探索和研究,可以帮助我们进一步理解非常规高温超导的物理起源。文章对近年来镍基超导材料的发展进行了概述,主要包括镍基薄膜中超导电性的发现;112相的晶体结构和电子结构;薄膜生长条件的优化及相关研究进展和相图。最后,对镍基超导材料的发展给出简要总结和展望。 相似文献
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新型激光晶体Yb:KY(WO4)2的结构与光谱 总被引：1，自引：0，他引：1
采用顶部籽晶提拉法,以K2W2O7为助溶剂,生长了Yb:KY(WO4)2新型激光晶体.经热重-差热分析,确定晶体熔点为1045℃,相变温度为1010℃.X射线粉末衍射测试,验证所生长的晶体为β-Yb:KY(WO4)2.晶体结构分析确定Yb:KY(WO4)2晶体由WO6八面体连接而成,WO6八面体是由双氧桥(WOOW)及单氧桥(WOW)构成.晶体粉末样品室温下的红外及拉曼光谱测试,确定WO6原子基团、双氧桥及单氧桥的振动频率.晶体的吸收峰位于940nm,980nm,发射峰位于989nm—1030nm.关键词：晶体结构光谱晶体生长 相似文献
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In the Eliashberg integral equations for d-wave superconductivity, two different functions (α 2F )n (ω , θ ) and (α 2F )p ,d (ω ) determine, respectively, the “normal” self-energy and the “pairing” self-energy. ω is the frequency of fluctuations scattering the fermions whose momentum is near the Fermi-surface and makes an angle θ to a chosen axis. We present a quantitative analysis of the high-resolution laser based Angle Resolved Photoemission Spectroscopy (ARPES) data on a slightly under doped cuprate compound Bi2212 and use the Eliashberg equations to deduce the ω and θ dependence of (α 2F )n (ω , θ ) for T just above T c and below T c. Besides its detailed ω dependence, we find the remarkable result that this function is nearly independent of θ between the (π; π)-direction and 25 degrees from it, except for the dependence of the cut-off energy on θ . Assuming that the same fluctuations determine both the normal and the pairing self-energy, we ask what theories give the function (α 2F )p ,d (ω ) required for the d-wave pairing instability at high temperatures as well as the deduced (α 2F )n (θ , ω ). We show that the deduced (α 2F )n (θ , ω ) can only be obtained from antiferromagnetic (AFM) fluctuations if their correlation length is smaller than a lattice constant. Using (α 2F )p ,d (ω ) consistent with such a correlation length and the symmetry of matrix-elements scattering fermions by AFM fluctuations, we calculate T c and show that AFM fluctuations are excluded as the pairing mechanism for d-wave superconductivity in cuprates. We also consider the quantumcritical fluctuations derived microscopically as the fluctuations of the observed loop–current order discovered in the under-doped cuprates, and which lead to the marginal Fermi–liquid properties in the normal state. We show that their frequency dependence and the momentum dependence of their matrix-elements to scatter fermions are consistent with the θ and ω dependence of the deduced (α 2F )n (ω , θ ). The pairing kernel (α 2F )p ,d (ω ) calculated using the experimental values in the Eliashberg equation gives d-wave instability at T c comparable to the experiments. 相似文献
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氧化锌晶体的水热法生长及性能表征 总被引：2，自引：0，他引：2
报道以块状氧化锌陶瓷为培养料,KOH、LiOH和H2O2的混合水溶液为矿化剂体系,采用水热法生长出尺寸为30mm×38mm×8mm的氧化锌晶体。氧化锌晶体 c(0001)和-c(0001)方向的生长速度分别为0.17,0.09mm/day。 c面的颜色为浅绿色,而-c面的颜色为深褐色。在室温下测得 c面的载流子浓度为104cm-3,电阻率为80Ω·cm,迁移率为100cm2/V·s。晶体(0001)面的双晶摇摆曲线的FWHM为45arc-sec。对氧化锌晶体 c面在室温条件下的光致发光谱和吸收光谱进行了测试分析。 相似文献