bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-Ray Absorption and Resistivity Studies of the Quinary-Compound Superconductor Y-Ba-Cu-O-S
Authors: Spagna S. , Althoff J. , Yao Y. D. , Xu F. , Jang L. Y. , Krol A. , Kao Y. H. 
Published: March 2011

ABSTRACTA quinary-compound system consisting of Y, Ba, Cu, O, and S has been prepared in our laboratory. The nominal composition of Y, Ba, Cu, and O is similar to the well known material YBa2Cu3O7-y; the addition of S is intended to partially substitute the O sites. X-ray absorption measurements show that the lattice is distorted with the presence of S atoms. The transition temperature is found to decrease from 93K to about 77K with an increasing S content up to a S/Cu concentration ratio near 0.25; further increase of S results in unstable superconducting behavior and very broad resistive transition.
High-Tc Superconducting Films of Y-Ba-Cu Oxide Prepared by a Low Pressure Plasma Spraying
Authors: Tachikawa K. , Watanabe I. , Kosuge S. 
Published: March 2011

ABSTRACTA low pressure plasma spraying technique for depositing high-Tc YBCO thick films has been developed. Films with thickness ranging 20–100 μm have been prepared using Y0.3Ba0.7CuOx powders. After post-annealing in oxygen for 1h at 930–950°C, the films, which were deposited on nimonic alloy substrate heated at 650°C during spraying, exhibited a zero resistance temperature of 90.6K with transition width (90%-10%) of 2K and a critical current density (77K, 0T) of 690 A/cm2.
A Hydroxycarbonate Route to Superconductor Precursor Powders
Authors: Voigt J. A. , Bunker B. C. , Doughty D. H. , Lamppa D. L. , Kimball K. M. 
Published: March 2011

ABSTRACTA precipitation process is described for the preparation of powders that can be thermally decomposed to form high critical temperature superconductors such as YBa2Cu3O7. In the process, a cationic solution (a concentrated chloride or nitrate solution) is instantaneously mixed with an anionie solution (a mixture of tetramethylammonium hydroxide and carbonate) to produce a metal-hydroxycarbonate precipitate having the metal stoichiometry of the desired superconducting oxide. The calcining and sintering of the precipitates is critical in controlling the structural integrity and morphology of the superconducting ceramics made from the chem-prep powders, as well as controlling superconducting properties. Under appropriate conditions, high density (>95%) materials that exhibit good superconducting characteristics can be prepared with the chem-prep powders.
Effect of Uniaxial Strain on the Superconducting Transition Temperature in thin YBa2Cu3O7 Film
Authors: Park S. I. , Scheuermann M. R. , Chi C. C. , Tsuei C. C. 
Published: March 2011

ABSTRACTThe effect of uniaxial strain e on superconducting transition temperature Tc of thin YBa2Cu3O7 film is presented. The value of TC increases linearly with compressional strain with a slope of -275K/e. Under tensile strain, Tc initially decreases to a value ∼ 0.3K below the zero-strain value and then remains constant with additional strain. In compression, the logarithmic strain derivative of Tc, (1/Tc)(dTc/de), is -3 per unit strain which is slightly less than 4–6 per unit strain observed in conventional superconductors.
Deposition of High Tc Superconductor thin Films by Pulsed Laser Ablation
Authors: Mashburn D. N. , Geohegan D. B. , Eres D. , Lowndes D. H. , Boatner L. A. , Sales B. C. , Pennycook S. J. , Culbertson R. J. , Sonder E. , Christen D. K. 
Published: March 2011

ABSTRACTThin superconducting films of YBa2Cu3O7 and HoBa2Cu3O7 have been obtained by ablating material from high-Tc bulk superconductor ceramics onto a nearby substrate using focused excimer laser radiation. Subsequent annealing in oxygen at elevated temperatures was necessary to achieve the superconducting phase. A range of deposition and annealing conditions was investigated to yield films of the desired stoi chiometry and phase.
Superconducting thin Films of (RE)Ba2Cu3(Ag)O7x Prepared by Pulsed Laser Ablation
Authors: Lynds L. , Weinberger B. R. , Peterson G. G. , Krasinski H. A. 
Published: March 2011

ABSTRACTThin films of (RE)-Ba-Cu-O perovkites containing silver were prepared by pulsed Nd:YAG (wavelength 1064 nm) laser ablation. Presence of the 1:2:3 phase was verified by scanning Auger microscopy. Onset of the d.c. resistive superconducting transition of 85 K was observed. Films with and without silver were compared and the potential benefits of silver inclusion are discussed.
High Tc Superconducting Y-Ba-Cu-O Thick Fim by Screen Printing
Authors: Yen H. H. , Kung J. H. , Chen Y. C. , Wu P. T. 
Published: March 2011

ABSTRACTSuperconducting film of ternary copper oxides from the Y-Ba-Cu-O system has been prepared by screen printing on 96% A1203 substrate with onset temperature at 95K and zero resistance at 85K. X-ray diffraction patterns show that film will react with the A1203 substrate. With decreasing film thickness the superconductivity is destroyed and may become a semiconductor.
The Morphology of YBa2Cu3O7−x Thin Films Grown on Ceramic Substrates
Authors: Tietz L. A. , De Cooman B. C. , Carter C. B. , Lathrop D. K. , Russek S. E. , Buhrman R. A. 
Published: March 2011

ABSTRACTThe microstructure of thin films of the high Tc superconductor YBa2Cu3O7−x deposited on SrTiO3 and Y-stabilized cubic-zirconia (YSZ) single-crystal substrates has been characterized by transmission electron microscopy. Films on both substrates were polycrystalline. On {001 }-oriented SrTiO3, the grains are oriented with <110> normal to the substrate surface. On the same orientation of YSZ, two microstructures are observed: one in which grains have their c-axes normal to the substrate surface, the other in which grains have the a- (or b-) axis normal to the substrate surface. Both of these microstructures contain special grain boundaries. Annealing of ion-milled TEM specimens is presented as a means of removing ion-beam damage.
Laser Induced Deposition of YBa2Cu3O7−x Thin Films
Authors: Kwok H. S. , Mattocks P. , Shaw D. T. , Shi L. , Wang X. W. , Witanachchi S. , Ying Q. Y. , Zheng J. P. , Bush P. 
Published: March 2011

ABSTRACTWe describe here the deposition of the YBaCuO superconducting thin films by the laser evaporation technique. The characterization of this process, and possible optimization with regards to wavelength and pulse duration of the laser will be discus sed.
Thermal Conductivity of Single-Crystal and Sintered RBa2Cu3O7 at low Temperatures
Authors: Graebner J. E. , Schneemeyer L. F. , Cava R. J. , Waszczak J. V. , Rietman E. A. 
Published: March 2011

ABSTRACTThe thermal conductivity k of micro-twinned single crystals of YBa2Cu3O7 and HoBa2Cu3O7 and a sintered sample of YBa2Cu3O7 has been measured for temperatures 0.03<T<5K. For the single crystals, k is small and varies as T1.8-1.9 This behavior resembles k for glassy insulators except for the lack of a plateau above IK. It is concluded that the thermal carriers are phonons with their mean free path limited by resonant scattering from tunneling entities, as in glasses. Suggestions for the location of tunneling systems are given. For the sinter, k is still smaller but does not follow a power law T-dependence. It is similar to other sintered ceramics with the same particle size, where the phonon mean free path is dominated by Rayleigh scattering from the particles. This strong scattering from the microstructure presumably masks the scattering from TS within each particle.
Electrical Conductivity and Thermogravimetric Studies of the High-7c Superconductor YBa2Cu3Ox
Authors: Han Y. H. , Monroe D. W. 
Published: March 2011

ABSTRACTNonstoichiometry in YBa2Cu3Ox has been studied by means of equilibrium electrical conductivity and thermogravimetric method. We have observed a strong correlation between electrical resistivity and oxygen stoichiometry (x) at high temperature. Electrical resistivities increase linearly from the superconducting onset tcmperature(100 K) to 450 C where oxygen starts to evolve from this material, and then begin to deviate from linear temperature dependence. The experimental results indicate that electrical resistivity in this material is associated with the defect species (charge carrier) population due to oxygen stoichiometry. Electrical conductivities were also measured as a function of oxygen partial pressure (1 to 10−4 atm) at various temperatures. At P(OI) > 101 atm the conductivity shows a l/4th slope dependence on oxygen partial pressure while at P(0;) < 10 f atm the conductivity is proportional to P(O2)1/2- The conductivity behavior with oxygen stoichiometry suggests that the electron holes associated with Cu+ play an important role as charge carriers in this material, and even at x < 6.5 p-typc conduction is predominant.
Optical Reflectance Studies on YBa2Cu3O7−x and Related Compounds
Authors: KamaráS K. , Doss M. G. , Herr S. L. , Kim J. S. , Porter C. D. , Stewart G. R. , Tanner D. B. , Bonn D. A. , Greedan J. E. , O'reilly A. H. , Stager C. V. , Timusk T. , Keszei B. , Pekker S. , Hutiray Gy. , Míhaly L. 
Published: March 2011

ABSTRACTOptical reflectance spectra in the range 30–35000 cm-1 and 4–300 K are presented on several YBa2CuxOy phases, as well as different forms of the superconducting YBa2CuxO7−x (polycrystalline pellets, textured pellets with ab-plane oriented surface, and single crystals).
Mechanism of Je Enhancement of YBa2Cu3O7-α Due to Ag-Doping
Authors: Kung J. H. , Yen H. H. , Chen Y. C. , Wang C. M. , Wu P. T. 
Published: March 2011

ABSTRACTAg-doping was found to enhance the critical current density of the ceramic superconductors by as much as a factor of 15. This Jc enhancement is due to both the increased amount of the superconducting phase and the resulting preferred crystal orientation. The optimum level of dopant may vary according to the chemical forms of Ag dopants.
Effect of Water and Iron on Slowly and Rapidly Cooled Y-1 Ba2Cu3O6+x Superconductors: An EPR/NMR Study
Authors: Brahme U. S. , Kordas G. , Kirkpatrick R. J. 
Published: March 2011

ABSTRACTWe present here a study of the effect of Fe doping and hydration on the NMR, EPR spectra and Tc of slowly and rapidly cooled Y-1 Ba2Cu3O6+x Superconductor. The g-values of the EPR signals are related to Cu2+ ions in six-fold coordination. Tc is suppressed 10–20°C due to changes in processing conditions and the addition of Fe. The 89Y MAS-NMR spectra show that Y is more shielded (more ionically bonded) in the slowly cooled sample than in the rapidly cooled sample and the hydrated slowly cooled sample is less shielded. The effect of hydration on 89Y chemical shift is consistent with the presence of protons near the Y.
Grain Boundary Segregation and Thermal History Effects on Properties of La1.85Sr0.15CuO4-y Superconductors
Authors: Chiang Yet-Ming , Roshko Alexana , Fabes Brian D. , Leung Dominic K. , Ikeda Jeri Ann S. , Rudman David A. , Parker Michael J. , Martin John R. 
Published: March 2011

ABSTRACTThe grain boundary segregation of Sr in the La1.85Sr0.15CuO4-y system, and its effects on polycrystalline diamagnetic properties, have been characterized. Equilibration at 1000°C reduces grain boundary segregation compared to that which is present at 700°C. Results indicate that critical currents in randomly oriented polycrystalline materials will be improved if annealing treatments can be optimized to minimize grain boundary segregation without degrading lattice oxygen stoichiometry.
Absorption Component of the Magnetic Susceptibility in Superconducting YBa2Cu3O7
Authors: Durny R. , Ducharme S. , Hautala J. , Symko O. G. , Taylor P. C. , Kulkarni Sudhir 
Published: March 2011

ABSTRACTMicrowave absorption measurements from 20 to 80 K in magnetic fields up to 12 kG are reported. Below a certain characteristic temperature T* = 80 ± 2 K < Tc the absorption in magnetic-field-cooled samples is smaller and broader in comparison to the zero-field-cooled samples. The incident microwave radiation induces a dc voltage across the sample which is also magnetic field dependent and peaks at zero magnetic field.
Light-Induced Current Suppression of Superconducting YBa2Cu3O7-δ Weak Link
Authors: Kawabe U. , Nishino T. , Tarutani Y. , Hasegawa H. 
Published: March 2011

ABSTRACTThe high-T oxide-superconductor YBa2Cu3O7-δ is expected to be a low carrier-density material having optical ana nonequilibrium properties. Light can penetrate the superconductor and can effectively excite the quasi-particles in it. To clarify the nonequilibrium phenomenon, we have studied this oxide superconductor exposed to light.
Preliminary Results on YBCO/Nb Bulk Junction
Authors: Barone A. , Di Chiara A. , Peluso G. , Pepe G. , Russo M. , Scotti Di Uccio U. 
Published: March 2011

ABSTRACTCurrent-voltage characteristics and dV/dI curves of a YBCO/Nb bulk junction at 4.2 K are reported. The presence of the Josephosn effect is clearly shown. The dV/dI spectrum shows sharp structures which can be related to the Niobium and the YBCO energy gaps Δnb and ΔNb and ΔYBCO. A value ΔYBCO = 26.2 ± 1.0 meV can be estimated, confirming the strong coupling character of such a compound.
Irradiation Effects Induced by 2.5 MeV-Electrons and 2.9 GeV-Krypton Ions in the High Tc Superconducting Oxides
Authors: Studer F. , Prouost J. , Groult D. , Raveau B. , Bouffard S. , Toulemonde M. , Jousset J. C. 
Published: March 2011

ABSTRACTThe resistivity measurements of bulk super-conducting oxides La2−xSrxCuO4−x/2+ 〈0.15〈x〈0.2) irradiated by 2.5 Mev-electrons and YBa2Cu3O7-δ 〈0〈δ〈0.15) irradiated by 2.9 GeU-krypton ions have shown a regular and constant decrease of the critical temperature Tc as a function of the fluence.On the contrary, an increase of Tc has been observed durino irradiation of super-conduct ino La2CuO4 compound by 2.9 GeV-krypton ions, which saturates at Tc/Tco = 0.1 for fluences hioher than 3.1012 Kr.cm−. The evolution of the R(T) curves during irradiation is very similar to the one observed under Dressure.A comparison of the variations of Tc as a function of the number of di solacements oer atom for various particles (n. e−. He+. O. Kr) suggests that the hijjh electronic stoppino power of the heavy ions could be the main factor of damage.
A Study of the Tetragonal-To-Orthorhombic Transition of YBa2Cu3Ox by Dilatometry
Authors: Han S. C. , Wu Z. L. 
Published: March 2011

ABSTRACTAn YBa2Cu3Ox bar specimen was air annealed at 930°C followed by water quenching under protection of a quartz sheath, then annealed at a series of temperatures between 300° -500°C. Isothermal dilatation curves were measured at each annealing temperature. An Avrami type plot of these data gave rise to an activation energy H=1.2eV for the tetragonal-to-orthorhombic reaction. It is suggested that this is the activation enthalpy of oxygen diffusion in the tetragonal phase which remains continuous and therefore rate controlling throughout the whole course of transition. Based upon this transition process, we expect a fully annealed specimen to be composed of numerous superconducting domains separated by a continuous film of semiconducting tetragonal phase, one or two molecular layers thick. At the points of contact, this film is highly strained by the impinging domains, rendering the material superconductive by S/N/S junctions.
X-Ray Study of Superconducting Y1Ba2Cu3−xFexOy Compounds
Authors: Gonzalez G. , Rios-Jara D. , Akachi T. , Barrio R. , BañOs L. , Escudero R. 
Published: March 2011

ABSTRACTSuperconducting compounds of Y1B2C3−xFexOy, with x=0.125, 0.0625, 0.125 and 0.300, were studied using X-ray powder diffractometry. Two sets of samples were prepared. Samples quenched from 950°C to liquid nitrogen temperature showed a tetragonal non-superconducting phase, whose lattice parameters depend on the Fe content and differ from those of the yttrium 1:2:3 tetragonal phase. Samples oxygenated at 450°C showed an orthorhombic to tetragonal phase transition for Fe contents higher than x=0.0625. The lattice parameters of this tetragonal phase were different from those of both tetragonal phases mentioned above. All these observations allow us to conclude that C(l) sites are occupied at least partially by Fe impurities.
Neutron Diffraction Studies of High TC Superconductors
Authors: Hinks D. G. , Dabrowski B. , Zhang K. , Segre C. U. , Jorgensen J. D. , Soderholm L. , Beno M. A. 
Published: March 2011

ABSTRACTWe have investigated the structure and composition of La2CuO4 (both pure and Sr-doped) and Nd(Ba2−xNdx)Cu3O7 using powder neutron diffraction. In La2−xSrxCuO4, Tc reacnes its maximum at x=0.15, after which vacancies are introduced in the 2D planes and superconductivity is destroyed. Superconductivity in La2CuO4 is not bulk. No evidence for nonstoichlometry in this material can be observed. In the Nd(Ba2−xNdx)Cu3O7 system, Tc is a complex function of oxygen ordering and electronic effects.
Thermal Cycling Degradation of YBa2Cu3O9−x Superconductors
Authors: Kinser Donald L. , Magruder Robert H. , Quarles Ronald A. , Dora Schaefer J. 
Published: March 2011

ABSTRACTThermal cycling for four cycles between 294 and 78°K has been observed to shift the superconducting transition temperature from 85 to 28°K. Samples cycled for 12 cycles between 373 and 78°K do not display superconductivity at temperatures down to 37°K. Guinier de Wolff X-ray diffraction observations of these samples reveal no crystallography changes during thermal cycling up to 12 cycles. Scanning electron microscopy studies of polished samples of the thermally cycled material revealed the presence of cracks in individual grains within each sample. The percentage of grains displaying cracks climbs rapidly with thermal cycling. We conclude that the loss of superconducting behavior is a consequence of removal of continuous paths but we are not, at this time, able to rationalize the shift of Tc with thermal cycling. We conclude that the thermal expansion anisotropy produces strains which lead to destructive fractures within the material.
The Microscopic Study of Y-Ba-Cu-O Compound
Authors: Lin W. T. , Chu H. C. , Chen B. H. , Chang Y. H. , Chin T. S. , Wu P. T. 
Published: March 2011

ABSTRACTThe microstructure of Y-Ba-Cu-O compound, sintered at 950°C for 16h, was examined by using transmission electron microscope(TEM). For the furnace cooling sample, two variants of–orthorhombic YBa2-Cu3O7−x (O-Y123) twins, grown on (110) and (110) planes, respectively, are crystallographically related to the matrix and produce a Widmanstatten morphology. The orientation relationship between the lath twin and the matrix is (001)T//(001) and [100]T//[010]M. The O-Y123 compound is unstable under tne electron irradition. Twin boundaries are identified as S-boundaries. The minor phases as Y2BaCuO5 (Y211) and BaCuO2 were also observed. For the air cooling sample, no superconductivity above 77K was found. The major phase is tetragonal Y123 (T-Y123), while small amount of 0-Y123 is also existent.
Atom Probe Microanalysis of Superconducting YBa2Cu3O7−x
Authors: Brenner S. S. , Kellogg G. L. 
Published: March 2011

ABSTRACTSuperconducting YBa2Cu3O7−x needles prepared from hot-pressed discs of oxide powders were analyzed in a long drift-tube type atom probe. An analyses was made from a randomly located area about 2 nm in diameter. Most of the oxygen field-evaporated as O2+ ions. The measured composition agreed well with that of YBa2Cu3O6.5 except for yttrium which was found to be too high. The oxygen concentration profile showed fluctuations about 2.5 nm apart which must still be clarified.
Theoretical Studies of Copper Oxide Clusters: Prediction of an Electronically Driven Phase Separation in YBa2Cu3Ox
Authors: Curtiss L. A. , Brun T. O. , Gruen D. M. 
Published: March 2011

ABSTRACTOn the basis of semi-empirical extended Hiickel molecular orbital calculations of copper-oxide clusters representing the new superconducting material YBa2Cu3Ox, a phase diagram is proposed which suggests that the 94 K high temperature superconducting phase of YBa2Cu3Ox is characterized by an oxygen stoichiometry near 7.0. The phase diagram predicts that a plateau should exist for Tc in the region x = 0.0 – 0.25 and that in this region two phases are present which are characterized by compositions having oxygen stoichiometries 6.5–6.75 and ca. 7.0.
Properties and Structures of Copper Rich Y-Ba-Cu-O Superconductors
Authors: Drehman A. J. , Horrigan J. A. , Dumais M. W. 
Published: March 2011

ABSTRACTCopper rich Y-Ba-Cu-O samples were prepared by reacting and sintering powders. The resultant material is composed of YBa2Cu3Oy and CuO. Proper processing results in a 85% dense, well interconnected material with a superconducting transition temperature of 92K. Zero resistance is observed even though a quarter of the volume is the CuO phase. This is because the CuO phase is in the form of isolated grains and not at the grain boundaries of the superconducting matrix.
Twins in YBa2Cu3O7-δ
Authors: Gibbons P. C , Kelton K. F. , Li Z.-Y. , Mantese L. , Sobotka L. 
Published: March 2011

ABSTRACTHigh-resolution TEM images of well-characterized YBa2Cu3O7-δ prove that atomic disorder in the {110} twin boundaries is confined to within 20 A of the boundaries, and suggest that there is disorder within those regions.
The Granular Behavior of LaSrCuO: Oxygen Concentration Effects on the Electrical Resistivity
Authors: Osquiguil E. , Civale L. , Decca R. , Safar H. , Martinez E. , Nieva G. , De La Cruz F. 
Published: March 2011

ABSTRACTElectrical resistivity measurements of the superconductor La1.80sr0.20CuO4-δ over a Wide range of temperatures and oxygen concentration, together with the analysis of superconducting properties of the material, indicate that the ceramic superconductors are high < materials in the clean limit. The granular superconducting behavior is determined by the oxygen content.
Inversion of First-arrival Time Using Simulated Annealing
Authors: Tran Khiem T. , Hiltunen Dennis R. 
Published: March 2011

A technique is presented to invert first-arrival time using simulated annealing. The scheme is based on an extremely fast finite-difference solution of the Eikonal equation to compute the first-arrival time through the velocity models by the multistencils fast marching method. The core of the simulated annealing, the Metropolis sampler, is applied in cascade with respect to shots to significantly reduce computer time. In addition, simulated annealing provides a suite of final models clustering around the global solution and having comparable least-squared error to allow determining uncertainties associated with inversion results. The capability of this inversion technique is tested with both synthetic and real experimental data sets. The inversion results show that this technique successfully maps 2-D velocity profiles with high variation. The inverted wave velocity from the real data appears to be consistent with cone penetration test (CPT), geotechnical borings, and standard penetration test (SPT) results.
A q-deformed particle algebra with a unique d-dimensional representation
Authors: Tekin Şeyda , Arik Metin 
Published: March 2011

Abstract
We present an algebra generated by a single pair of creation and annihilation operators b and b*. We prove that the algebra has a unique d-dimensional representation. Physically this algebra corresponds to a system where there are at most d − 1 particles in a state with otherwise same quantum numbers.