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Investigation of the Size Effect on the Giant Dielectric Constant of CaCu3Ti4O12 Ceramic

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Chinese Physics Letters 2004年第9期21卷 1815-1818页

作者：陈恺李伟刘云飞包鹏吕笑梅朱劲松 NationalLaboratoryofSolidStateMicrostructuresandDepartmentofPhysics NanjingUniversityNanjing210093

Cubic perovskite-related ceramic CaCu3Ti4O12 has a very high dielectric constant larger than 10000 in the kilohertz frequency region. It is almost constant in the 100–600K region. The ceramic compounds were prepared by conventional solid-state reaction at different sintering temperatures 1040 degrees C(C04), 1060 degrees C(C06), 1080 degrees C(C08), and 1100 degrees C(C10). Impedance spectroscopy on CaCusTi4O12 ceramics demonstrates that they are electrically heterogeneous and consist of semi-conducting grains with insulating grain boundaries. It is shown that C06 is the most suitable one for device applications. Surface observation and analysis of the grain-boundary-grained structure were carried out by using scanning electron microscopy, which confirms that the samples have clearly different crystal grain sizes and C06 has a larger grain size of about 20μm. Compared to the dielectric relaxation spectroscopy, the mechanical relaxation spectroscopy on C06 was performed and a mechanical loss peak was found, which was attributed to the thermally activated behaviour being immanent in the grains.

关键词： copper compounds

20-W sealed-off CuBr vapour laser excited with modified Blumlein circuit

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Chinese Optics Letters 2007年第10期5卷 591-593页

作者：毛邦宁潘佰良王煜博陈立王丽敏 Department of Physics Zhejiang University

A sealed-off CuBr vapour laser with the maximal average output laser power of 20 W was fabricated and investigated. The corresponding efficiency is 1.2% and the specific average output laser power is 123 mW/cm^3 in an... 详细信息

关键词： copper compounds Energy conversion Energy efficiency Power generation Vapors

Fabrication and Characterization of YBa2Cu3Oy Superconducting Nanowires

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Chinese Physics Letters 2005年第3期22卷 651-653页

作者：李培刚符秀丽陈雷明张海英李玲红唐为华 BeijingNationalLaboratoryforCondensedMatterPhysics InstituteofPhysicsChineseAcademyofSciencesBeijing100080 DepartmentofPhysics BeijingNormalUniversityBeijing100875 DepartmentofPhysics UniversityofRhodeIslandRI02881USA

Ordered YBa2Cu3Oy nanowires have been fabricated by filling YBa2Cu3Oy melting liquid into the pores of the anodized alumina templates. X-ray powder diffraction proves that YBa2Cu3Oy nanowires crystallized in the Y-123 structure. The temperature dependence of ac susceptibility indicates a superconducting transition at 91K for the YBa2Cu3Oy nanowire array.

关键词： copper compounds

Multiple-Scattering Approaches to Near-Edge X-Ray Absorption Fine Structure of N2O／Cu（100）

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Chinese Physics Letters 2004年第8期21卷 1586-1589页

作者：吴太权唐景昌沈少来曹松李海洋 DepartmentofPhysics ZhejiangUniversityHangzhou310027

The nitrogen 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of the N2O adsorbed on the Cu(100) surface have been studied by multiple-scattering cluster (MSC) and self-consistent field DV-Xα methods. It is shown that the N2O molecule is adsorbed on the hollow site with the adsorption height h = 3.0±0.1Å. The MSC calculation confirmed by a DV-Xα analysis has revealed the physical cause of the weak feature in the NEXAFS spectra mentioned above, which originates from the 1s core electrons of the centre and terminal nitrogen atoms transiting into the unoccupied σ* orbital of the N2O molecule.

关键词： copper compounds

Barrier Formation on a YBa2Cu3Oy Thin Film Using CF4 Plasma Fluorination

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Chinese Physics Letters 2002年第6期19卷 850-853页

作者：阿巴斯康琳等 ResearchInstituteofSuperconductorElectronic DepartmentofElectronicScienceandEngineeringNanjingUniversityNanjing210093 ResearchInstituteofSuperconductorElectronic DepartmentofElectronicScienceandEngi

We investigate the surface structure and composition of a YBa2Cu3Oy (YBCO) thin film modified by CF4 plasma fluorination. In addition to the absorption of hydrocarbons, chemical reactions of the YBCO surface take place during CF4 plasma treatment. Various x-ray photoelectron spectroscopic data are reported and discussed. The existence of a thin barrier is confirmed, which homogeneously covers the edge of the base YBCO film in our interface engineering Josephson junction. Measurements of Auger electron spectroscopic data and the resistance versus temperature indicate that the barrier is a controllable-insulating layer.

关键词： copper compounds

Features in Quasi—particle Excitations and Tunnelling Spectra due to Coupling to Spin Fluctuations in High—Tc Cuprates

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Chinese Physics Letters 2002年第7期19卷 992-995页

作者：赵力李建新等 NationalLaboratoryofSuperconductivity InstituteofPhysicsChineseAcademyofSciencesBijing100080 NationalLaboratoryofSolidstatesofMicrostructureandDepartmentofPhysics NanjingUnivers

In a self-consistent mean-field treatment of the two-dimensional t-t'-J model, we theoretically examine the coupling of in-plane quasi-particles to the antiferromagnetic spin fluctuations in high-Tc superconductors, which renormalizes the fermionic self-energy. We reproduce the characteristic peak-dip-hump structure observed not only in angle-resolved photoemission spectroscopy, but also in superconductor-insulator-normal metal junctions and scanning tunnelling microscopy experiments. We consider the evolution of this structure with doping. It is shown that this kind of coupling can account for many anomalous properties of high-Tc superconductors in superconducting states.

关键词： copper compounds

Magnetic Field Dependence of the Critical Current of Bi2Sr2CaCu2O8＋δ-Based Intrinsic Josephson Junctions

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Chinese Physics Letters 2004年第4期21卷 726-728页

作者：朱晓波魏彦锋赵士平陈赓华杨乾声 KeyLaboratoryofExtremeConditionsPhysics InstituteofPhysicsandCenterforCondensedMatterPhysicsChineseAcademyofSciencesBeijing100080

Well-characterized surface intrinsic Josephson junctions (IJJs) on Bi2Sr2CaCu2O8+δ single crystals are fabricated by in situ cryogenic cleavage of the crystals and immediate evaporation of Au films on the crystal surface. Magnetic field dependences of the critical currents of the surface and inner IJJs are carefully measured. We find that the critical current behaviour of the surface IJJs in magnetic field is quite different from that of the inner junctions. The behaviour of the inner IJJs can be understood to be of large stacked junctions described by the coupled sine-Gordon equations, while the surface IJJs behave like a separate single large junction. These results indicate that the coupling between the surface IJJ and the inner IJJs is weaker than the coupling among the inner junctions.

关键词： copper compounds

Electron—Phonon Coupling in Anion Metallic Solids and Superconducting MgB2

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Chinese Physics Letters 2002年第8期19卷 1176-1178页

作者：尹道乐杨帆等 DepartmentofPhysics PekingUniversityBeijing100871

We analyse the Hopfield factor of the newly found superconductor MgB2 using the linear muffin-tin orbital method. Based on a uniform transferred charge density model raised, it is shown from our calculation that the high difference of electronegativity between boron and magnesium favours the high l(l + 1) angular momentum hybridization and then the Hopfield factor. Our analysis is consistent with experimental results. Comparisons with cuprate superconductors are also discussed.

关键词： copper compounds

Superconductivity of Bi1.6Pb0.4Sr2Ca3Cu4O12

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Chinese Physics Letters 2002年第12期19卷 1863-1865页

作者： AtillaCoskun AhmetEkicibil 等 DepartmentofPhysics FacultyofSciencesandLettersCukurovaUniversity01330BalcaliAdanaFurkey

The superconducting ceramics Bi1.6Pb0.4Sr2Ca3Cu4O12 have been prepared by the melt-casting method. A zero resistance temperature at 60K has been observed. It has been found that the superconducting phase temperature Tc increases with increasing sintering temperature. The effect of Pb content on the superconductivity of the ceramic has been studied. The microstructure of the sample has been investigated by scanning electron microscopy. Phase analysis has been carried out by x-ray diffraction patterns and energy dispersive analysis through x-ray spectroscopy.

关键词： copper compounds