bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cation Interdiffusion at YBCO/MgO Interfaces
Authors: Lanham M. , Mayer J. , Golden S.J. , Lange F.F. , Rühle M. 
Published: March 2011

AbstractResistivity measurements of YBCO thin films on MgO substrates show that the transition to the superconducting state depends on film thickness. TEM investigations of the films revealed interdiffusion of Cu and Mg. The concentrations of the cations at the interface were quantitatively measured. These data show that their diffusion rates are much different (MgODCu/YBCODMg=30); this indicates that the diffusion mechanism is complicated by the layered structure of the perovskite-like films. No impurity segregation was detected at the interface. Diffraction study of several YBCO grains confirms that the film c-axis is oriented perpendicular to the substrate, but that the a/b plane has no fixed orientation, indicating that no epitaxial relationship exists.
Evaluating the Chemical Compatibility of Potential Substrate Materials for Bi-Sr-Ca-Cu-O Films
Authors: Williams K.E. , Matthiesen M.M. , Rudman D.A. 
Published: March 2011

AbstractPotential substrate and buffer layer materials for Bi2Sr2CaCu2Ox (BSCCO) were surveyed using bulk ceramic processing techniques. Of the materials tested, only Ag was inert with respect to BSCCO. MgO slightly degrades the superconducting onset temperature and volume fraction. LaGa03 may be a feasible ceramic substrate for BSCCO, although some reaction appears to occur.
Formation of Sputtered Y-Ba-Cu-O Superconducting Thin Film on Metal Substrate
Authors: Hayakawa H. , IIJIMA Y. , Sadakata N. , Kohno O. 
Published: March 2011

AbstractY1Ba2Cu3O7-x superconducting composites have been prepared on metallic substrate by rf magnetron sputtering method. Buffer layer of thin SrTiO3 layer between superconducting film and the substrate was found to be effective to realize superconductivity. Preferable grain alignment of c-axis was also obtained. The critical current density at 77K was 2.2x103 A/cm2 with Tc at 83K, and it was found that the thicker films had the higher Jc values.
Fabrication of YBa2Cu3O7-x Filaments by Extrusion of a Cu3O3Ba2Y(meoEt)7 (meoEt = 2-Methoxyethoxide) Precursor
Authors: Rupich M. W. , Cogan S. F. , Lagos B. , Hachey J. P. 
Published: March 2011

AbstractYBa2Cu3O7-x filaments, with a zero resistance Tc of 89.5 K and a Jc of 225 A/cm2 in zero field at 77 K, were prepared from precursor filaments fabricated by extrusion of a polymeric Cu-Ba-Y precursor. The precursor was prepared by reaction of linear a (CuO)n polymer with Y and Ba alkoxides in non-aqueous solvents. Characterization of the precursor and superconducting filaments, along with the optimum extrusion and pyrolysis conditions, are described.
Processing and Performance of Metal Fiber Reinforced High Temperature Superconductor
Authors: Salib S. , Vipulanandan C. , Stone T. 
Published: March 2011

AbstractAggregation of YBa2Cu3O7‐x powder by compaction molding and sintering results in porous ceramic with poor mechanical properties and hence improving the ceramic properties using continuous stainless steel fibers have been studied. Fiber reinforced beam specimens (2% of fibers by weight) were prepared by modifying the standard processing method. Fibers were pretreated with silver to reduce the contamination of the superconducting matrix. The mechanical and electrical properties of the superconducting ceramic‐fiber composite was evaluated at 77K. Continuous stainless steel fibers improved the performance of the superconducting ceramic.
X-Ray Characterization of the Crystallization Process of High-TC Superconducting Oxides in the Sr-Bi-Pb-Ca-Cu-O System
Authors: Wong-Ng Winnie , Chiang Chwan K. , Freiman Stephen W. , Cook Lawrence P. , Hwang Nong M. , Hill Michael D. 
Published: March 2011

AbstractPhase assemblages in two Sr-Bi-Pb-Ca-Cu-O glasses and their crystallization into glass-ceramics through a sequence of heat treatments are described. Samples were heat treated at various temperatures based on differential thermal analysis (DTA) analysis of the as-quenched glasses. X-ray powder diffraction was used to identify the compounds in each sample; and the different phases formed in these two samples were compared. Results of microstructural characterization of selected samples using scanning electron microscopy are discussed.
Thermal Annealing Study of High-TC Ybacuo and Bisrcacuo Superconducting Wires
Authors: Yao Y. D. , Chen J. W. , Chen Y. Y. , Pern W. S. , Yong H. A. , Lin I. N. , Yao P. C. , Yang S. J. , Hsu S. E. 
Published: March 2011

AbstractHigh‐T YBaCuO and BiSrCaCuO Superconducting wires have been fabricated by powder metallurgy technique. Copper and silver tubes were used as the external jackets. Thermal annealing treatments for all the wire‐type samples were performed between 773 K and 1223 K. Both electrical and magnetization studies show that the superconducting properties can be improved after properly thermal annealing these samples with silver jacket. Our experimental results show that proper thermal annealing treatment can enhance the intragrain critical current density more than 100 times; however, the intergrain critical current density improves only a few times.
The Interface Between High Tc Superconductors and Silver Contacts
Authors: Mcconnell Malcolm D. , Morris William G. 
Published: March 2011

AbstractSilver diffuses into the lattice of YBa2Cu307 during the annealing of silver contacts at 500°C. Depth profiles using Auger electron spectroscopy, with a focused electron beam, show an extensive diffusion zone, as well as segregation of barium and oxygen to the surface of the contact. There appears to be a slight loss of silver from the surface region, which could be explained by enhanced concentration at grain boundaries. High resolution SEM analysis of a fracture surface did not reveal the presence of silver on the grain boundaries. Diffusion rates were correlated with grain orientation by using magnetically aligned samples, and were found to be greater for the direction parallel to the C axis.
Role of Silver in Yba2Cu3AgXO7-δ Composite Superconductors
Authors: Ganapathi L. , Kumar Ashok , Narayan J. 
Published: March 2011

AbstractSuperconducting properties and microstructures of the YBa2Cu3AgxO7‐δ composites have been studied as a function of silver content, 0 ≤ x ≤ 6, using a variety of techniques.The superconducting transition temperature,Tc, of these composites was found to be the same, ∼ 90 K, for the above range of compositions. The composites with x > 3 are found to have resistivity behavior identical to silver metal above the superconducting transition temperature. The peritectic transformation temperature of the 123 material in the composite is lowered. Alloy formation between Ag and Cu is proposed to take place triggering the peritectic transformation at lower temperatures. The silver is observed in the form of precipitates at very low concentrations of silver, indicating that silver does not substitute for copper in YBa2Cu3AgxO7. Lattice parameters of the composites were found to be invariant throughout the above composition range. The addition of Ag2O in the starting composition seems to stabilize the stoichiometric YBa2Cu3AgxO7 by way of decomposition to Ag and O, also, the better diffusion of oxygen through silver in comparison with that through the superconductor helps the regeneration of superconductivity in the composite superconductor. As a result, the incorporation of oxygen and recovery of superconducting properties is enhanced in the silver composites.For values of x > 3 small quantities of 211 phase were detected along the grain boundaries, which makes the residual composition poor in copper resulting in the formation of non‐superconducting 211 phase.
The Effect of the Distribution of Ag in High TC Bi- Compound Superconductors
Authors: Nash Alexis S. , Goretta K. C. , Nash Philip , Poeppel R. B. , Shi Donglu 
Published: March 2011

AbstractA series of 4336 Bi‐Sr‐Ca‐Cu oxide samples doped with 1 to 5% metallic Ag was prepared by solid state reaction. The distribution of Ag, the microstructure and the crystal structure of the samples were studied using energy dispersive spectrometry, EDS, scanning electron microscopy, SEM, and x‐ray diffractometry, XRD. Addition of Ag leads to a marked increase in preferred orientation with (001) planes perpendicular to the pressing direction in sintered pellets. The resistivity‐temperature data show an enhanced Tc in Ag‐doped samples under certain conditions. Energy dispersive spectrometry indicates that the dopant mostly segregates to the grain boundaries.
Growth of nd2‐xcexcuo4‐y Singlk Crystals by a Flux Method
Authors: PiñOl S. , Miravitlles C. , Fontcuberta J. , Paul D. Mck. 
Published: March 2011

AbstractWe have investigated single‐crystals growth of Nd2‐xCexCu04‐y By using a flux method. The phase diagram Nd203 ‐CuO has been determined For a number of compositions. In addition, the corresponding diagram for some Nd2O3CeO2‐CuO composition is also reported. Plate single crystals having dimensions up to 5 x 5 x 0.2 m have been prepared by the melt mixtures from 1250℃ to 800℃ at a rate of 5℃/h.The yield of CeO2 concentration in the starting compositions and the corresponding x values in the crystals has been investigated in order to improve superconducting properties of the crystals. Superconducting single crystals have been found from flux compositions 70% CuO, (30‐z)% NdO1.5and z% of CeO2 with 2.50 < z < 4 5.
Synthesis, Transport And Microstructural Properties of Nd1.85Ce0.15CuO4‐δ
Authors: Lee Jong‐Gyu , Ramanujachary K.V. , Greenblattî M. 
Published: March 2011

AbstractThe n‐type superconductor, Nd1.85Ce0.15CuO4‐δ has been prepared by solid state reaction and solution precursor techniques under various conditions and characterized by means of X‐ray diffraction, magnetic susceptibility, electrical resistivity and SEM measurements. Samples prepared by solution method displayed higher normal state resistance but better superconducting volume fractions than those prepared by conventional ceramic techniques. In addition, the solution precursor technique reduces the sintering temperature from 1150°C (used for solid‐state route) to 1000°C in achieving the superconducting phase. The solution‐route yields particles with relatively uniform size distribution, but poor connectivity between the grains. In contrast, the solid state preparations yield well connected grains but with a larger distribution of sizes. The observed differences in the superconducting properties of samples prepared by different techniques have been attributed to the differences in their microstructure.
Activation Energy of Decomposition of Y2bacuo5 Compound in Wet Co2 at Elevated Temperatures
Authors: Simmins John J. , Hanagan Michael J. , Fischman Gary S. , Snyder Robert L. 
Published: March 2011

AbstractDecomposition of the Y2BaCuO5 in C02 was studied using simultaneous thermal analysis (STA) and X-ray diffraction (XRD). The time derivative to the thermo-gravimetric analysis data (DTG) was used to calculate the activation energy. The activation energy of decomposition by CO2 into barium carbonate, copper oxide and yttrium oxide was found to be <
High Tc Oxide Solid State Reaction Kinetics Via Complex Impedance Spectroscopy
Authors: Cooper E. A. , Mason T. O. , Balachandran U. , Kullberg M. L. 
Published: March 2011

AbstractImpedance spectra (5Hz ‐ 13MHz) were collected during the solid state reaction of Yba2Cu2O6+y from large monosized CuO particles imbedded in a finely divided Y2 O3 /BaCO3 matrix. No particle size effect was observed, but a large temperature effect was observed corresponding to an activation energy of approximately 1.8eV (175kJ/mol) over the range 700‐900°C.
Synthesis of Unidirectionally Solidified Y‐Ba‐Cu‐0 Bulk Superconductors with High Critical Current Densities
Authors: Yanagisawa E. , Kondoh S. , Shimoyama J. , Kase J. , Matsubara T. , Morimoto T. 
Published: March 2011

Abstract(Y,Ho)‐Ba‐Cu‐0 superconductors with the high critical current densities (Jc) in an applied magnetic field have been synthesized by a unidirectional melt solidification method. Melt solidified bulk materials are composed of large plate‐shape (Y,Ho)Ba2Cu3Oy crystals which contain small (∼5 um) particles of (Y.Ho)2BaCuO5. The Jc value of the melt solidified (Y,Ho)‐Ba‐Cu‐0 sample is ∼10000 A/cm2 at 77K, H = IT and this value is much higher than the value of 4200 A/cm2 of the melt solidified Y‐Ba‐Cu‐O sample.
New Method for Synthesizing Bi-Sr-Ca-Cu-O Superconductor
Authors: Tanaka Masahiro , Habu Kazutaka 
Published: March 2011

AbstractCeramics of the phase Bi2Sr2Ca2Cu3O10 (2223) without Pb are synthesized by a modified conventional ceramic process. The influence of the absence of Pb is observed in the lattice constant.
Preparation of 110k Superconductor in Bi-Sr-Ca-Cu-O System
Authors: Zuyao Chen , Rong Lin , Xianhui Chen , Yitai Qian 
Published: March 2011

AbstractTo explore high Tc in Bi-Sr-Ca-Cu-O system, many different nominal compositions have been prepared by using the traditional solid state reactions and using the method of crystallizion from glass samples. The better results are as follows: single high-Tc phase and essentially single high-Tc phase have been obtained from Bi1.8Pb0.35Sr2Ca2Cu3O and Bi2Sr2Ca6Cu7O respectively, by solid reaction. Basically single hign-T phase material with nominal composition Bi2Sr2Ca3Cu4Oy has been produced by the method of crystallizion from glass samples. The relationship between the starting composition heat treatment, preparation methods and high Tce is briefly discussed.
Relation Between the Characteristics of Powder and Microstructure; Properties of Ceramics for YBa2Cu2Ox Superconductors
Authors: Zhao Meiyu , Li Chengen , Jin Xingyun , Huang Yeming , Zhou Enji , Ni Huanyao , Qu Yaoming , Song Xiangyun , Wu Wenjun 
Published: March 2011

AbstractFour kinds of YBa2Cu2Ox (YBCO) superconducting powders with different particle sizes, shapes and different amounts of twins have been prepared in this work. The density, grain sizes, XRD of phase composition, configuration of twins of the ceramics have been investigated. The relation between the characteristics of YBCO powders and the microstructure, current density of the bulk materials are also discussed. In contrast to the YBCO powder prepared by solid state method, the YBCO powders through the improved coprecipitat ion approach have less impurities, smaller particle size and much more amounts of twins, as well as the sintered pellets show a higher density, an orthorhombic single phase, and moreover, the pellets have finer grain boundaries and well developed twins. As a result these samples exhibit current densities (about 1500 A/cm2) higher than those prepared by solid state method. Using BaOx instead of BaCO3 as the starting material, a more dense bulk YBCO ceramics with orthorhombic single phase and Jc (about 1,000 A/cm2) can have also been fabricated by solid state mat hod.
Pulsed Laser Deposition of High Tc Superconducting Thin Films: Deposition Physics and in-Situ Processing
Authors: Singh Rajiv K. , Narayan J. 
Published: March 2011

AbstractThe pulsed laser evaporation (PLE) technique for deposition of thin films is characterized by a number of unique properties. Based on the experimental characteristics, a theoretical model is developed which considers the formation and anisotropic three dimensional expansion of the laser generated plasma. This model explains most of the experimental features observed in PLE. We have also employed the PLE technique for in-situ fabrication of YBa2Cu3O7 superconducting thin films on different substrates in the temperature range of 500–650°C. At temperatures below 600–C, a biased interposing ring between the substrate and the target was found to significantly improve the superconducting properties. The minimum ion channeling yields were between 3-3.5 % for films deposited on (100) SrTiO3 and (100) LaA1O3 substrates. The films exhibit very high critical current densities (Jc) with maximum values exceeding 6.5 x 106 amps/cm2 for silver doped YBa2Cu3O7 films on (100) LaA1O3 substrates, and the Jc also varies anisotropically with the magnetic field.
In Situ Growth of High Quality Epitaxial Yba2cu3O7‐X Thin Films at Moderate Temperatures by Pulsed Laser Ablation
Authors: Lowndes Douglas H. , Norton David P. , Mccamy J. W. , Feenstra R. , Budai J. D. , Christen D. K. , Poker D. B. 
Published: March 2011

AbstractPulsed KrF (248 nm) laser ablation has been used for in situ growth of smooth, high‐quality YBa2Cu3O7‐x epitaxial films of variable thickness on SrTiO3, KTaO3, LaGaO3, LaA1O3, cubic ZrO2, and MgO substrates, at temperatures of ∼60O‐730°C, without higher temperature post‐annealing. A rotating target pellet, fine focusing by a single cylindrical lens, laser‐beam scanning over the target, and laser energy densities ∼2.5‐3 J/cm2 can be combined to yield films of completely uniform composition and with ∼25% thickness variation over areas ∼8 cm2. The best films have Tc > 92 K and JC(H = 0, T = 77 K) > 2 MA/cm2. Film‐growth procedures are described, together with results of superconducting and normal‐state transport measurements.
The Influence of Target-Substrate Bias on Pulsed Laser Deposited Yba2Cu307-6
Authors: Chrisey D.B. , Horwitz J.S. , Grabowski K.S. , Reeves M.E. , Osofsky M.S. , Gossett C.R. 
Published: March 2011

AbstractWe have deposited YBa2Cu307.$ thin films onto <100> SrTi03 substrates at 700°C as a function of target‐substrate bias (0 to 300 V) in order to make use of the positive ions in the laser produced plume to assist in the deposition. The films were extensively characterized to determine differences in film properties (composition, structure, and transport). The results suggest that film properties were optimized at or near a target‐substrate bias of 100 V, although, the differences in film properties were within the margin of reproducibility.
Pulsed Laser Deposition of High TC Superconducting Thin Films
Authors: Russek S.E. , Moeckly B.H. , Buhrman R.A. , McWhirter J.T. , Sievers A.J. , Norton M.G. , Tietz L.A. , Carter B. 
Published: March 2011

AbstractIn this paper we present results of studies of the effect of process variations and substrate surface conditions on the microstructure and electrical properties of laser deposited YBa2Cu3O7‐δ thin films. The principle conclusions are as follows. The film properties of YBa2Cu3O7‐δ are relatively constant over a large range of substrate temperatures (620C‐720C) and oxygen pressures (150‐800 mT). There are small compositional variations with substrate temperature similar to, but much smaller than, those seen in reactively sputtered films. The best films were grown at 670C in 400mT of oxygen and have a zero resistance Tc of 89K and Jc > 1x106A/cm2 at 77K. There are, however, variations in the Tc, Jc, and orientation of films grown on MgO under similar deposition conditions. These variations reflect differences in the nucleation and growth process of YBa2Cu3O7‐δ on MgO which can arise from subtle changes in substrate surface properties. In particular, while the films are predominantly oriented with c axis perpendicular and a,b axes in the plane of the substrate along the MgO[100] direction, there are variable amounts of grains whose in‐plane orientations are at large angles to the MgO [100] direction, leading to large angle grain boundaries in some films. These large angle grain boundaries are correlated with the presence of Josephson weak links in some small constrictions for films on MgO.
In-Situ Processing of Epitaxial and Textured High Tc Superconducting Hoba2Cu3O7.X Thin Films By Pulsed Laser Evaporation Technique
Authors: Lee C. B. , Prasad R. , Singh A. K. , Sharan S. , Singh R. K. , Tiwari P. , Narayan J. , Holland O. W. , Boatner L. A. 
Published: March 2011

AbstractExcellent quality epitaxial and textured superconducting HoBa2Cu307.x (Ho 123) thin films have been fabricated on lattice matched (100) KTaO3 and (100) LaAlO3, and lattice mismatched (100) MgO substrates by the pulsed laser evaporation (PLE) technique. A bulk Hol23 target was evaporated using nanosecond excimer laser pulses with the evaporating material depositing on a substrate maintained in the temperature range of 550‐650°C. The temperature for zero resistance for HoBa2Cu3O7_x films deposited on various substrates at 650°C varied between 85 to 89K. The epitaxial films deposited on (100) LaA103 substrates exhibited critical current densities greater than 3.5 x 106 Amps/cm2 at 77 K. The superconducting properties of the Ho 123 films were found to be similar to Y123 films.
Study of In‐Situ Laser‐Deposition of Superconducting Thin Films by In‐Situ Resistance Measurement
Authors: Ying Q.Y. , Kim H.S. , Shaw D.T. , Kwok H.S. 
Published: March 2011

AbstractThe electric resistance was measured in real time during laser evaporation deposition of superconducting thin films. It was found that different substrates led to different behaviors in the temporal change of the resistance. The results are consistent with the processes of nucleation, interface reaction and bulk‐like growth. Structural transformation was also observed due to oxygen backfilling at the final stage of the deposition.
Arf Laser Ablation of Yba2Cu3O7‐X as Studied by Emission Spectroscopy, Sem and Edax
Authors: Hoffman Alon , Manory Rafael R. 
Published: March 2011

AbstractThe fluorescence emission spectra from the plasma plume induced by ArF excimer laser irradiation of YBa2Cu3O7‐x was studied and compared to the spectra of Y, YO, Cu, CuO, and YCuO under similar conditions. The only compound detected in the Y‐Ba‐Cu‐O ablated material spectra was YO. Spatially resolved measurements from the plasma plume emanating from the irradiated superconducting material were performed also as a function of distance from the surface.The effect of laser ablation on the morphology and composition of the irradiated YBa2Cu3O7‐x material was studied by SEM and EDAX. It was found that the 1‐2‐3 composition ratio of the near surface region was maintained after ablation. Changes in the morphology were observed in the track region and three distinctive regions could be identified as a function of distance from the beam center.
Textured Superconducting Thin Films of Bismuth Cuprate by Laser Ablation Method
Authors: Kumar Ashok , Ganapathi L. , Narayan J. 
Published: March 2011

AbstractWe have prepared highly textured superconducting thin films from Bi1.5pb0.5Ca3Sr2Cu4Ox (2324) on (100) YS-ZrO2 (Yttria stabilized zirconia) and Bi1.5Pb0.5Ca2Sr2Cu3°x (2223) on LaAlC-3 (100) and MgO (100) substrates at 650°C by pulsed laser ablation method.These films showed 2212 type of phase of the (BiPb)2(Ca,Sr)n+1CunO2n+4+5 family with onset transition temperature ( Tc ) ~ 110 K, confirming our earlier observations of 110 K superconductivity in a n = 2 bulk material. Thin films deposited from 2324 bulk target on YS-Z1O2 showed zero resistance temperature (Tco ) of 68 K but post annealing for one hour at 400°C in oxygen improved Tco from 68 K to 82 K. Thin films from 2223 target on LaAlO3 ( 100 ) and MgO ( 100 ) exhibited a Tco of 65 K and 74 K respectively while onset remained the same at 110 K. Further annealing at 400°C for one hour in oxygen did not show any improvement in Tco. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rutherford backscattering (RBS) channeling studies were performed on these films for correlation between crystal structure, microstructure and superconducting properties. X-ray diffraction patterns indicated 2212 type phase with a= 5.39 Å and c=30.76 Å; preferential orientation of c-axis perpendicular to the substrate was observed. The lattice parameter and x-ray diffraction patterns were found to be invariant with annealing treatments.