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本文结合有效价键模型和原子对势的理论计算研究了Tl-1223超导相的Cu-O金字塔五配位上由于Fe掺杂所导致的额外氧效应。研究结果表明Fe掺杂原子占据Cu晶位后,将导致额外氧进入晶格而占据Ca原子四方网络的间隙位置。 相似文献
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本研究了La2CuO4+δ体系中额外氧的掺杂效率和低温下的超导相图。当氧一较低时,每个额外氧向铜氧面提供两个空穴;而当δ〉0.03时,每增加一个氧则平均只提供1.3个空穴。在La2CuO4+δ体系中首次发现了15K反常现象,这种反常不是由晶体相变诱导的。 相似文献
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在Ar+O22气氛中,采用射频反应溅射Cd-In靶制备CdIn22O44 薄膜.制得的薄膜经x射线衍射(XRD)检测为CdIn22O44和CdO相组成的多晶.从理论上分析了热 处理前后氧空位、掺杂点缺陷和富氧电子陷阱在影响膜的载流子浓度和电子散射中所起的重要作用.同时,对样品 进行Hall效应、Seebeck效应测试并得出不同载流子浓度下的迁移率、有效质量、弛豫时间以及它们之间的相互关系,特别强调 相似文献
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本用Recursion方法研究Al局域替代La1.85Sr0.15CuO4中的Cu引起的电子结构变化。认为Al替代后使得CuO2面空穴载流子浓度减少,这对超导电性有相当破坏作用;此外,因掺杂而诱导出的有效磁矩也对超导电性起部分破坏作用。 相似文献
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本文采用EXAFS方法了GdBa2Cu3O7-x高Tx超导陶瓷在不同温度下淬火后各金属原子周围氧配位数及键长的变化,得出该123相超导体随淬火温度升高失氧的具体位置为O1及O4,Cu-O平面未被破坏。指出Cu-O链及O4在123相超导体中应具有重要作用。 相似文献
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用标准固相反应法,我们制备了Bi1.6Pb0.4Sr2Ca2Cu3Oy和Bi2CaCu2Oy纯相样品,在液氮温度下测量了Cu-NQR和B-NQR静态谱,发现NQR谱都为大宽包,Cu-NQR谱线位置反映铜原子所处的氧环境,Bi2Sr2Cu2Oy的NQR谱宽反映其调制结构,Bi1.6Pb0.4Sr2Ca2Cu3OyNQR谱宽取决于其掺杂浓度。由于电场梯度弥散很大,Bi-NQR谱很难观察。 相似文献
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B. Seling A. Ehmann C. Schinzer J. Linhart W. Reimers S. Kemmler-Sack 《Zeitschrift für Physik B Condensed Matter》1995,99(4):517-520
In the system Bi-0212 the carrier concentration can be changed by both cation substitution and oxygen content. The crystal structure of Ca substituted material was refined from neutron powder diffraction data for Bi0.5Sr1.5Ca0.5Y0.5Cu1.5Fe0.5Oy. It is shown that extra oxygen is introduced in the cation layers between the double sheets of Cu/O pyramids. In superconducting material the familar dependence ofT c on the hole carrier concentration is observed. The higherT c is situated at 75 K. 相似文献
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B. Seling A. Ehmann C. Schinzer J. Linhart W. Reimers S. Kemmler-Sack 《Zeitschrift für Physik B Condensed Matter》1995,99(1):517-520
In the system Bi-0212 the carrier concentration can be changed by both cation substitution and oxygen content. The crystal
structure of Ca substituted material was refined from neutron powder diffraction data for Bi0.5Sr1.5Ca0.5Y0.5Cu1.5Fe0.5Oy. It is shown that extra oxygen is introduced in the cation layers between the double sheets of Cu/O pyramids. In superconducting
material the familar dependence ofT
c on the hole carrier concentration is observed. The higherT
c is situated at 75 K. 相似文献
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Bond covalency and valence of elements in HgBa2Can−1CunO2n+2+δ (n=1, 2, 3, 4) were calculated and their relationship with Tc was discussed. For both oxygen and argon annealed samples, the results indicated that with the increase of n, the trend of bond covalency of Hg-O and Cu-O was the same or opposite compared with that of superconducting temperature. This may suggest that the magnitudes of Cu-O and Hg-O bond covalency are important in governing the superconducting temperature. For the highest Tc sample, Hg had the lowest valence, implying that lower valence of Hg was preferred in order to produce higher Tc. For fixed n, the valence of Cu in oxygen annealed samples was larger than that in argon annealed samples, indicating that oxygen annealed samples produced more carriers than argon annealed samples. 相似文献
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对高品质单相多晶Bi2Sr2CaCu2O8+δ样品作真空或H2气氛中不同温度下的热处理。由X射线结构分析,其正常态和超导态性质(特别是载流子浓度)的系统测量结果表明:Bi2Sr2CaCu208+δ样品在H2气氛中热处理,其氧的释放可分为两个阶段:一是Bi-O层之间的过量氧原子的逸出,降低系统的载流子浓度,从而调节Tc;二是CuO2面内氧原子的迁移,产生氧空位,使CuO2面内Cu2+的短程二维反铁磁(2D-AFM)有序背景遭到破坏。可以认为:以往文献中报道的Bi2Sr2CaCu2O8+δ超导体的吸氢效应导致Tc的变化,很可能主要的并不是氢原子的电子掺杂行为,而是与吸氢过程中氧含量的变化相联系。
关键词: 相似文献
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V. Sankara Sastry S. Kalavathy B. K. Guha R. Baskaran U. De J. Janaki 《Phase Transitions》2013,86(1-2):97-105
Electrical resistance measurements at low temperatures and high quasihydrostatic pressures on superconducting and non-superconducting varieties of Y0.8Ba1.2Cu2O5 (obtained by annealing in oxygen and air respectively) show striking anomalies in the vicinity of 100K and 40K. Arguments are presented to show that these anomalies as also the occurrence of T 's in the oxide superconductors either in the vicinity of 100K or of 40K are connected with their layered structure containing planes of Cu-O otahedral complexes. 相似文献
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ZHOU Xian-Yi ZHANG Han YUAN Song-Liu WANG Shun-Xi ZHU Jing-Sheng ZHANG Qi-Rui 《中国物理C(英文版)》1991,15(11):961-965
The measurements of one-dimensional angular correlation of positron annihilation radiation (1D-ACAR) spectra,superconducting critical temperature,lattice parameters and oxygen contents have been made on YBa2-xSrxCu3Oy high temperature supercnductor system.It was found that the substitution of Sr for Ba weakens the orthorhombic symmery,suppresses TC,hardly changes oxygen content and does not disturb the electronic structure of Cu-O chains.Based on the above results.the authors propose that the localized electronic structure of Cu-O plane is a dominating factor for high temperature superconductivity in 1:2:3 phase superconductors. 相似文献
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We have studied doping evolution of the temperature dependent local Cu-O displacements in the La2-x
Sr
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CuO4 superconductor by polarized Cu K-edge extended X-ray absorption fine structure (EXAFS) measurements. While temperature dependent Debye-Waller factor of the Cu-O bonds, measuring the local Cu-O displacements, shows an anomalous increase at low temperature for the underdoped single crystals, we do not find such a dependence for the case of the overdoped system. The results, which are discussed in the light of recent angle resolved photoemission measurements, provide an evidence for some important correlation between the doping dependent electron-lattice interaction, the charge inhomogeneities and the local Cu-O displacements in the copper oxide superconductors.Received: 9 July 2003, Published online: 19 November 2003PACS:
74.72.Dn La-based cuprates - 61.10.Ht X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc. - 74.81.-g Inhomogeneous superconductors and superconducting systems 相似文献