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1.
Makoto Takahashi Yuuko Tomioka Toshiyuki Miyauchi Shoji Sato Asami Murai Toshiyuki Ido Koichi Wakita Hiroshi Terada Sadao Ohkido Masanori Matsubara 《Journal of the American Ceramic Society》2007,90(7):2032-2037
A slurry containing YBa2 Cu3 O7− x particles and a fine YBa2 Cu3 (OH) x colloid solution was prepared, and a large-scale bulk YBa2 Cu3 O7− x superconductor (about 50 mm × 35 mm × 2 mm) was produced by plastic forming without high-pressure molding. The samples molded from the slurry were dried and then fired at 1223 K in air. X-ray diffraction data indicated that the samples had the characteristic orthorhombic YBa2 Cu3 O7− x structure. Measurements of electrical resistance were carried out between 300 and 50 K by the standard four-probe DC electrical measurement. The samples began superconducting at an onset temperature around 92 K, and the full-transition temperature (critical temperature) ( T c ) was 88.7±1.4 K. The critical current density ( J c ) measured at 77 K was about 440 A/cm2 , the value of J c was improved by the heat treatment under an oxygen atmosphere, and J c =1.6 × 103 A/cm2 was observed. Under the magnetic field (B=1 T), the sample held its superconductivity, and demonstrated that this method can be used to produce the magnetic shielding used in magnetic resonance imaging diagnosis. 相似文献
2.
Solid-state sintering was used to make YBa2 Cu3 O7−δ superconducting bulk materials. Corrosion of the YBa2 Cu3 O7−δ superconductor material was investigated in a humid environment. The superconducting materials exhibited significant corrosion after 4 h at 80° and 100% relative humidity. A grain-boundary phase was formed, and the percent superconducting phase in the material decreased by approximately 60%. The transition temperature (Tc ) decreased with corrosion time. After 2 h of corrosion, Tc decreased from 87 to 81 K. 相似文献
3.
Ji-Ping Zhou Charles C. Sorrell Shi-Xue Dou Miles H. Apperley 《Journal of the American Ceramic Society》1991,74(7):1541-1546
The present work describes a new technique to synthesize aligned YBa2 Cu3 O7- x and Ag─YBa2 Cu3 O7- x superconducting composites from Ba- and Cu-deficient compositions (relative to YBa2 Cu3 O7- x ) plus BaCuO2 . For YBa2 Cu3 O7- x , high transition temperature midpoint Tc (91 K), temperature of zero resistivity T 0 (90 K), and critical current density Jc (>3000 A°Cm−2 at 77 K) were achieved by using this technique. This procedure provides the potential for using a reliable and reproducible densification and alignment technique alternative to partial or full melting. The composite is highly aligned, with an average grain size of ∼1 to 2 mm and domains of width greater than 5 mm. The initial phase assemblage consists of YBa2 Cu3 O7- x (123) as the major phase plus YBa2 CuO5 (211) CuO as minor phases. The BaCuO2 is added to the Ba- and Cu-deficient starting composition in order to assist in the formation of a CuO-rich liquid as well as to compensate for the Ba and Cu deficiences in 123. Since the liquid forms at ∼900°C and is compatible with 123, it can be used to facilitate alignment of 123 at ∼930°C. The addition of Ag to the system results in eutectic formation with the (solidified) liquid, substantial filling of the pores during sintering, and improved alignment. 相似文献
4.
The (YBa2 Cu3 )1−x Nax O7–δ system in the range of x = 0–0.8 was investigated. Experimental data suggest that the sodium doping with x 0.26 does not affect the critical transition temperature Tc , and the crystal structure maintains the orthorhombic lattice with a slightly smaller unit cell. However, sodium doping increases the sintering and grain growth kinetics, resulting in a higher superconducting phase volume and an enhanced Meissner effect. It also lowers the processing temperaturel. The experimental data also suggest that the sodium atoms diffuse into the superconducting YBa2 Cu3 O7−δ crystallites, which stabilizes the orthorhombic phase. The transition temperature (ortho-rhombic to tetragonal) in sodium-doped materials increases with the increasing concentration of sodium. 相似文献
5.
Suguru Suzuki Shinji Asada Minoru Takahashi Yasuo Hikichi 《Journal of the American Ceramic Society》1991,74(4):714-717
The effect of extrusion on improving the critical current density ( J c ) of Bi1.4 Pb0.6 Sr2 Ca2 Cu3 O x superconducting wires is investigated. Calcined powders (Bi1.4 Pb0.6 Sr2 Ca2 Cu3 O x ) are first mixed with a forming aid—a thermoplastic polymer (polyethylene)—for workability, and then extruded, using a capillary rheometer, to form wires 2 mm in diameter. The J c value, measured by the four-probe method in liquid nitrogen at 77 K, is improved substantially by the following process: (1) the superconducting precursors are extruded at high viscosity with a forming aid, to align the platelike particles unidirectionally; (2) the forming aid alone is carefully burned out, without destroying the extruded configuration; and (3) the extruded wires are annealed at 850°C in air for more than 96 h. 相似文献
6.
Wai Lo Hin-Tak Leung David A. Cardwell James C. L. Chow 《Journal of the American Ceramic Society》1997,80(3):813-816
The growth morphology of large YBa2 Cu3 O7−δ grains during peritectic solidification has been reported to be responsible for the generation of processing defects, such as platelets, and an inhomogeneous distribution of 211 particles, both of which influence significantly the superconducting properties of the fully processed material. The present study demonstrates both experimentally and theoretically the formation of local dendrites at macroscopically planar YBa2 Cu3 O7−δ growth fronts which propagate along different crystallographic directions and identifies these as key growth features of the peritectic solidification process. 相似文献
7.
P. G. Clem J. T. Dawley M. P. Siegal D. L. Overmyer J. J. Richardson J. A. Voigt T. A. Holesinger 《International Journal of Applied Ceramic Technology》2005,2(1):24-32
A variety of solution deposition routes have been reported for processing complex perovskite-based materials such as ferroelectric oxides and conductive electrode oxides, due to ease of incorporating multiple elements, control of chemical stoichiometry, and feasibility for large area deposition. Here, we report an extension of these methods toward long length, epitaxial film solution deposition routes to enable biaxially oriented YBa2 Cu3 O7−δ (YBCO)-coated conductors for superconducting transmission wires. Recent results are presented detailing an all-solution deposition approach to YBCO-coated conductors with critical current densities J c (77 K)>1 MA/cm2 on rolling-assisted, biaxially textured, (200)-oriented Ni–W alloy tapes. Solution-deposition methods such as this approach and those of other research groups appear to have promise to compete with vapor phase methods for superconductor electrical properties, with potential advantages for large area deposition and low cost/kA·m of wire. 相似文献
8.
Takayuki Komatsu Michiko Ueta Tomohiro Ohki Ryuji Sato Kazumasa Matusita 《Journal of the American Ceramic Society》1992,75(7):1864-1869
The Ba-doped superconducting (Bi,Pb)2 Sr2- x Ba x Ca2 Cu3 O y and (Bi,Pb)2 Sr2 Ca2- x Ba x Cu3 O y (0 ≦ x ≦ 1.0) were prepared by using a melt-quenching method, and the effect of Ba additions on the glass-forming ability and the crystalline phase was examined. The glass-forming ability was not improved by substitution of Ba for Sr or Ca, and particularly BaPbO3 as well as CaO was observed in the melt-quenched sample of (Bi,Pb)2 SrBaCa2 Cu3 O y . BaPbO3 crystals were precipitated in all glass-ceramics with Ba substituted for Sr or Ca. The partial substitution of Ba substituted for Sr was effective for the formation of the high- T c phase, and (Bi,Pb)2 Sr1.4 Ba0.6 Ca2 Cu3 O y glass-ceramics obtained by annealing at 830°C for 100 h exhibited superconductivity with a T c of 103 K, although BaPbO3 and the low- T c phase were still largely present. 相似文献
9.
Won-Hyuk Lee Yoshihiro Abe Eikichi Inukai 《Journal of the American Ceramic Society》1993,76(4):849-856
Ag2 O-doped superconducting Bi2 Sr2 Ca1 Cu2 O x ceramics were prepared by a melt-quenching–reheating method. It is found that the Ag2 O-doped, as-cast specimens exhibit superconductivity ( T c = around 80 K) by heat treatment at temperatures around 800°C even in an evacuated and sealed silica glass tube, while the undoped specimens do not and vaporize by the corresponding heat treatment. Conversion of the Ag2 O-doped, as-cast specimens into superconducting ceramics when heated in an evacuated vessel is explained in terms of the oxygen donor of Ag2 O in the specimen. This finding enables us to fabricate a desired shape of superconducting Bi2 Sr2 Ca1 Cu2 O x ceramics sealed in metals or glasses. The addition of Ag2 O to Bi2 Sr2 Ca1 Cu2 O x melt, however, had deleterious influences on the superconducting properties ( T c and J c ) of the resultant ceramics when obtained by heat treatment in air. 相似文献
10.
Asha Mary John Rajan Jose Jose Kurian Poo Koodan Sajith Jacob Koshy 《Journal of the American Ceramic Society》1999,82(6):1421-1424
A new group of complex perovskites Ba2 REHfO5.5 (where RE = La, Pr, Nd, and Eu) has been synthesized and sintered as single-phase materials with high sintered density and stability using a solid-state reaction method for the first time. The structure of Ba2 REHfO5.5 has been studied by X-ray diffactometry (XRD) and all of the perovskites are isostructural and have a cubic structure. The dielectric constant and loss factor values of these materials are in a range suitable for their use as substrates for YBa2 Cu3 O7-delta superconductors. XRD and resistivity measurements show that there is no detectable reaction between YBa2 Cu3 O7-delta and Ba2 REHfO5.5 , even when the two substances are mixed thoroughly and sintered at 950°C for 15 h. The addition of Ba2 REHfO5.5 up to 20 vol% in YBa2 Cu3 O7-delta -Ba2 REHfO5.5 composite shows no detrimental effect on the superconducting transition temperature of YBa2 Cu3 O7-delta . Thick films of YBa2 Cu3 O7-delta fabricated on polycrystalline Ba2 REHfO5.5 substrate have a superconducting zero resistivity transition of 92 K, indicating the suitability of these new materials as substrates for YBa2 Cu3 O7-delta films. 相似文献
11.
M. J. Shapiro Karren L. More W. J. Lackey John A. Hanigofsky D. Norman Hill W. B. Carter E. K. Barefield Elizabeth A. Judson D. F. O'Brien R. Patrick Y. S. Chung T. S. Moss 《Journal of the American Ceramic Society》1991,74(8):2021-2024
High-resolution transmission electron microscopy and optical diffractograms have revealed that chemically vapor deposited films of superconducting YBa2 Cu3 O x react to form an interaction layer with single-crystal yttriastabilized zirconia. The approximately 5 nm thick interlayer was identified as BaZrO3 . Zirconium was also found to diffuse through the entire YBa2 Cu3 O x film. 相似文献
12.
Asok K. Sarkar Gregory Kozlowski Iman Maartense 《Journal of the American Ceramic Society》1990,73(10):3110-3112
A bulk density of 85% of the theoretical density was achieved by sintering a powder compact of YBa2 Cu4 O8 (124) at 850°C in flowing oxygen at 1 atm (≅105 Pa). This value is very close to that obtained by the hot isostatic pressure technique (90%). The superconducting properties of the sample were characterized by magnetization and ac susceptibility techniques. The magnetization critical current density at 20 K in zero field was determined to be ∼5 × 104 A/cm2 , and the superconducting transition temperatures were found to be 77 K for the bulk material and 82 K for the granular phase. The powder X-ray diffraction and ac susceptibility studies revealed the sintered 124 material to be single phase. 相似文献
13.
Sukill Kang Amit Goyal Keith J. Leonard Noel A. Rutter Dominic F. Lee Donald M. Kroeger Mariappan Parans Paranthaman 《Journal of the American Ceramic Society》2005,88(10):2677-2680
YBa2 Cu3 O7−δ (YBCO) films with thicknesses ranging from 1.0 to 6.4 μm were deposited by pulsed laser deposition on rolling-assisted biaxially textured substrates (RABiTS). The RABiTS were of the configuration CeO2 /YSZ/Y2 O3 /Ni–3 at.% W. As the YBCO film thickness increased, I c continued to increase and reached ∼300 A/cm width for a 4.3 μm-thick YBCO film. Commonly observed mechanisms for J c decrease with increasing YBCO film thickness were not observed. Homogeneous microstructures obtained in even the thickest YBCO films, suggest that the I c /width can still be enhanced considerably. 相似文献
14.
Yong Yan Jan E. Evetts Jin-li Zhang William M. Stobbs 《Journal of the American Ceramic Society》2000,83(5):1266-1272
The microstructure of partial-melt-processed YBa2 Cu3 O x /HfO2 has been studied by transmission electron microscopy. A characteristic spherulitic microstructure is formed in the system. A model for the growth mechanism has been proposed. The critical heterogeneous nucleation of the YBa2 Cu3 O x phase appears to occur from the melt in an epitaxially controlled manner on CuO particles. Subsequent growth of YBa2 Cu3 O x platelets from the nucleus region is repeatedly interrupted by the nucleation of hafnium-rich phases in the liquid at the solid/liquid interface in a manner that again appears to be epitaxially controlled and that promotes the splay of the c orientation of the YBaCuO grain. 相似文献
15.
Krzysztof Borowiec Jan Przyluski Krystyna Kolbrecka 《Journal of the American Ceramic Society》1991,74(8):2007-2010
The intrinsic kinetics, unaffected by diffusional and masstransfer effects, of the CO2 degradation of superconducting particles have been determined using a nonisothermal technique. Below 900°C, the carbonization of YBa2 Cu3 O7- x leads to formation of BaCO3 , Y2 Cu2 O5 , CuO, and Cu2 O. A further increase in temperature results in formation of BaCuO2 from BaCO3 and CuO. The carbonization rate shows the 1.5th-order dependence on the amount of unreacted YBa2 Cu3 O7- x for the temperature range of 550° to 815°C. The activation energy of carbonization was determined to be 95.1 kJ · mol−1 . 相似文献
16.
Mukesh K. Agarwala David L. Bourell Chadee Persad 《Journal of the American Ceramic Society》1992,75(7):1975-1977
Fine, homogeneous, dual-phase Ag–YBa2 Cu3 O7– x composite powders were prepared by a simple colloidal sol–gel coprecipitation technique that was previously used for synthesis of single-phase YBa2 Cu3 O7– x . Samples containing up to 60 wt% silver were synthesized. Silver neither reacted with nor degraded the YBa2 Cu3 O7– x . The presence of silver was found to aid the oxygenation of the precursor during calcination to form orthorhombic YBa2 Cu3 O7– x . Measurements made by ac magnetic susceptibility showed no significant degradation in transition temperature for samples containing up to 40 wt% silver. 相似文献
17.
Teen-Hang Meen Ying-Chung Chen Ken-Whie Liaw Hung-Duen Yang 《Journal of the American Ceramic Society》1993,76(8):1948-1952
X-ray diffraction patterns show that most samples of Y1-x Prx Ba2 Cu4 O8 examined in the present study contained a single YBa2 Cu4 O8 (1-2-4) superconductive phase for x<0.7.Lattice parameters a and b increased with Pr concentration, suggesting that most of the Pr is trivalent in Y1-x Prx- Ba2 Cu4 O8 . The zero-resistance temperature, T co , decreases monotonically from 80 K at x=0 to 12 K at x=0.65, and superconducting transition widths tend to broaden for x>0. The room-temperature resistivity changes linearly until x=0.7 and increases abruptly at x=-0.75. The critical concentration, xcr , thus was estimated to be 0.7. The effective magnetic moments of Pr in Y 1-x Prx Ba2 Cu4 O8 were 3.63., 3.35, and 3.23, μB for x=0.2, 0.4 and 0.6, respectively. In the R0.8 Pr0.2 Ba2 Cu4 O8 system, the depression of Tc weakly depends on the ionic radius of rare-earth elements. Similarities and differences between Y 1-x Prx Ba2 Cu4 O8 and Y1-x Prx- Ba2 Cu3 O7-y also were noted and are discussed in this paper. 相似文献
18.
The thermodynamic data for the Y2 O3 –BaO–Cu2 O–CuO quaternary system were optimized from measured thermodynamic data. A two-sublattice model for ionic solution was used to express the Gibbs free energy of the liquid phase, and a two-sublattice regular solution model was used for the nonstoichiometric YBa2 Cu3 O6+δ superconducting compound. The optimized thermodynamic data were used to calculate the phase diagrams of the Cu2 O–CuO binary system and the CuO x –Y2 Cu2 O5 and CuO x –BaCuO2 quasi-binary systems. The results were in good agreement with reported measured data. The liquidus projection and isothermal and vertical sections of the Y2 O3 –BaO-CuO x quasi-ternary system were calculated. The effect of oxygen pressure on some reaction temperatures was predicted by calculating them at various oxygen pressures, and the oxygen contents (6 +δ) in YBa2 Cu3 O6+δ were calculated at various temperatures and oxygen pressures. The results were compared with experimental data. 相似文献
19.
Y. Xu A. Goyal K.J. Leonard E.D. Specht D. Shi M. Paranthaman 《Journal of the American Ceramic Society》2006,89(3):914-920
YBa2 Cu3 O7− δ (YBCO or Y123) films on rolling-assisted biaxially textured substrates (RABiTS) were prepared via a fluorine-free metallorganic deposition (MOD) through spin coating, burnout, and high temperature anneal. The effects of substrate texture and surface energy of the CeO2 cap layer were investigated. Except for the commonly accepted key factors, such as the textures of substrate and buffer layers, we found some other factors, for example, the deposition temperature of the cap layer, are also critical to the epitaxial growth of Y123 phase. With the CeO2 cap layer deposited at relative high temperature of 700°C, a critical current density, J c , over 1 MA/cm2 has been demonstrated for the first time on Ni-RABiTS by a fluorine-free MOD method. Whereas for samples with CeO2 cap layers deposited at a lower temperature of 600°C, even though XRD data showed a better texture on these buffer layers, texture degradations of YBCO grains under the optimized processing conditions were observed and a lower oxygen partial pressure around 40 ppm was necessary for the epitaxial growth of Y123 phase. As a result, J c fell to 0.45 MA/cm2 at 77 K. The observed phenomena points to the change of surface energy and reactivity of the CeO2 cap layer with respect to the CeO2 deposition temperature. In this paper, the YBCO phase diagram was also summarized. 相似文献
20.
Takahiro Wada Hisao Yamauchi Shoji Tanaka 《Journal of the American Ceramic Society》1992,75(6):1705-1707
Concurrent thermogravimetry (TG) and evolved-gas analysis (EGA) were done for YBa2 Cu3 O7-z and LaBa2 Cu3 -O7-z superconductors. The sample weights were monitored by thermobalance and the evolved O2 and CO2 species were monitored by quadruple mass spectrometer (QMS). No diffraction peak for the impurity phase containing a carbonate group was observed in the X-ray diffraction patterns for these samples, but the release of CO2 was detected by EGA. CO2 gas began to evolve from YBa2 Cu3 O7-z at 543°C and from LaBa2 Cu3 O7-z at 692°C. Preparation of high-quality YBa2 Cu3 O7-z and LaBa2 Cu3 O7-z superconductors is discussed on the basis of results of these thermal analyses. 相似文献