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Practical superconductor development for electrical power applications - quarterly report for the period ending December 31, 2000

Description: This is a multiyear experimental research program focused on improving relevant material properties of high-T{sub c} superconductors (HTSs) and on development of fabrication methods that can be transferred to industry for production of commercial conductors. The development of teaming relationships through agreements with industrial partners is a key element of the Argonne National Laboratory (ANL) program. Recent results are presented on YBa{sub 2}Cu{sub 3}O{sub x} (Y-123) coated conductors, including fabrication by pulsed laser deposition (PLD) and sol-gel techniques. An approach to understanding the critical current density (J{sub c}) of grain boundaries is also presented and a technique is identified for increasing J{sub c}.
Date: January 15, 2001
Creator: Goretta, K.C.
Partner: UNT Libraries Government Documents Department

Erosion of magnesium potassium phosphate ceramic waste forms.

Description: Phosphate-based chemically bonded ceramics were formed from magnesium potassium phosphate (MKP) binder and either industrial fly ash or steel slag. The resulting ceramics were subjected to solid-particle erosion by a stream of either angular Al{sub 2}O{sub 3} particles or rounded SiO{sub 2} sand. Particle impact angles were 30 or 90{degree} and the impact velocity was 50 m/s. Steady-state erosion rates, measured as mass lost from a specimen per mass of impacting particle, were dependent on impact angle and on erodent particle size and shape. Material was lost by a combination of fracture mechanisms. Evolution of H{sub 2}O from the MKP phase appeared to contribute significantly to the material loss.
Date: November 20, 1998
Creator: Goretta, K. C.
Partner: UNT Libraries Government Documents Department

Annealing and mechanical properties of bulk Y-Ba-Cu-O.

Description: Single-domain melt-processed YBa{sub 2}Cu{sub 3}O{sub x}/Y{sub 2}BaCuO{sub 5} and conventional polycrystalline sintered YBa{sub 2}Cu{sub 3}O{sub x} pellets were prepared. Elastic modulus, hardness, and fracture strength were measured on selected sections cut from the pellets. Strength in the melt-processed pellets ranged from 32 to 94 MPa and was highest in the center. Variations in strength were related to microstructural features, especially Y{sub 2}BaCuO{sub 5} distribution. To improve strength, we attempted to minimize microcracking by manipulating cooling rates, annealing times, and oxygen partial pressure. Extent of cracking was evaluated by electron microscopy and change in elastic modulus and strength. We found that control of annealing reduced microcracking of the polycrystalline sintered pellets, but had little effect on the single-domain melt-processed pellets.
Date: September 11, 1998
Creator: Goretta, K. C.
Partner: UNT Libraries Government Documents Department

Development of oxide fibrous monolith systems.

Description: Fibrous monolithic ceramics generally have a cellular structure that consists of a strong cell surrounded by a weaker boundary phase [1-5]. Fibrous monoliths (FMs) are produced from powders by conventional ceramic fabrication techniques, such as extrusion [1,2]. When properly engineered, they exhibit fail gracefully [3-5]. Several compositions of ceramics and cermets have been processed successfully in fibrous monolithic form [4]. The most thoroughly investigated fibrous monolith consists of Si{sub 3}N{sub 4} cells and a BN cell-boundary phase [3-5]. Through appropriate selection of initial powders and extrusion and hot-pressing parameters, very tough final products have been produced. The resultant high toughness is due primarily to delamination during fracture along textured platelike BN grains. The primary objectives of our program are to develop: (1) Oxide-based FMs, including new systems with improved properties; (2) FMs that can be pressureless sintered rather than hot-pressed; (3) Techniques for continuous extrusion of FM filaments, including solid freeform fabrication (SFF) for net-shape fabrication of FMs; (4) Predictive micromechanical models for FM design and performance; and (5) Ties with industrial producers and users of FMs.
Date: March 2, 1999
Creator: Goretta, K. C.
Partner: UNT Libraries Government Documents Department

Microstructure and properties of Bi-Sr-Ca-Cu-O with nanometer-scale alumina additions.

Description: Al{sub 2}O{sub 3} particles {approx}30 nm is size were added to Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} in a 1:4 molar ratio. For comparison, 0.3 and {approx}3 pm Al{sub 2}O{sub 3} particles were added to separate batches. All materials were partial-melt processed. The Al{sub 2}O{sub 3} reacted during melting to primarily form stable compounds of approximate composition (Sr,Ca){sub 2}AlO{sub 4}. All additions caused slight decreases in the T{sub c} and melting point of the Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}. The submicrometer Al{sub 2}O{sub 3} additions induced large expansions in magnetic-hysteresis width at 6 K. Electron microscopy examinations strongly suggested that the hysteresis expansion was related to alloying of the Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} matrix rather than to pinning by volume defects.
Date: September 11, 1998
Creator: Goretta, K. C.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications. Annual report for FY 1992

Description: Development of useful high-critical-temperature (high-{Tc}) superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes the technical progress of research and development efforts aimed at producing superconducting components that are based on the Y-Ba-Cu, Bi-Sr-Ca-Cu, Bi-Pb-Sr-Ca-Cu, and (TI,Pb)-(Ba,Sr)-Ca-Cu oxide systems. Topics discussed are synthesis and heat treatment of high-{Tc} superconductors, formation of monolithic and composite wires and tapes, superconductor/metal connectors, characterization of structures and superconducting and mechanical properties, fabrication and properties of thin films, and development of prototype components. Collaborations with industry and academia are documented.
Date: October 1, 1992
Creator: Goretta, K. C.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications

Description: Development of useful high-critical-temperature (high-{Tc}) superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes technical progress of research and development efforts aimed at producing superconducting components based on the Y-Ba-Cu, Bi-Sr-Ca-Cu, Bi-Pb-Sr-Ca-Cu, and Tl-Ba-Ca-Cu oxides systems. Topics discussed are synthesis and heat treatment of high-{Tc} superconductors, formation of monolithic and composite wires and tapes, superconductor/metal connectors, characterization of structures and superconducting and mechanical properties, and fabrication and properties of thin films. Collaborations with industry and academia are also documented. 10 figs.
Date: October 1, 1991
Creator: Goretta, K.C. (comp.)
Partner: UNT Libraries Government Documents Department

Improved fracture toughness for copper oxide superconductors

Description: An oxide-based strengthening and toughening agent, such as tetragonal Zro{sub 2} particles, has been added to copper oxide superconductors, such as superconducting YBa{sub 2}Cu{sub 3}O{sub x} (123) to improve it fracture toughness (K{sub IC}). A sol-gel coating which is non-reactive with the superconductor, such as Y{sub 2}BaCuO{sub 5} (211) on the ZrO{sub 2} particles minimized the deleterious reactions between the superconductor and the toughening agent dispersed therethrough. Addition of 20 mole percent ZrO{sub 2} coated with 211 yielded a 123 composite with a K{sub IC} of 4.5 MPa(m){sup 0.5}.
Date: December 31, 1991
Creator: Goretta, K.C. & Kullberg, M.L.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications

Description: Development of useful high-critical-temperature (high-[Tc]) superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes the technical progress of research and development efforts aimed at producing superconducting components that are based on the Y-Ba-Cu, Bi-Sr-Ca-Cu, Bi-Pb-Sr-Ca-Cu, and (TI,Pb)-(Ba,Sr)-Ca-Cu oxide systems. Topics discussed are synthesis and heat treatment of high-[Tc] superconductors, formation of monolithic and composite wires and tapes, superconductor/metal connectors, characterization of structures and superconducting and mechanical properties, fabrication and properties of thin films, and development of prototype components. Collaborations with industry and academia are documented.
Date: October 1, 1992
Creator: Goretta, K.C. (comp.)
Partner: UNT Libraries Government Documents Department

Ultrasonic determination of the elastic moduli and their pressure dependences in very dense YBa{sub 2}Cu{sub 3}O{sub 7{minus}x}

Description: The effects of hydrostatic pressure and temperature have been measured on the velocities of longitudinal and shear ultrasonic waves propagated in a very dense (96% of theoretical density) ceramic specimen of YBa{sub 2}Cu{sub 3}O{sub 7{minus}x}. In YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} ceramics with such a high density the effects of porosity on the elastic properties should be much reduced. Nevertheless the bulk modulus of this dense material has the same small magnitude ({approximately} 55GPa) as that measured ultrasonically in much less dense YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} ceramics. The temperature dependences of the velocities of longitudinal and shear ultrasonic waves, which have been measured between 10 K and 300 K, show the step-like increase at 200 K on cooling and a similar decrease at 225 K during warming with hysteresis in the range 190 K to 235 K that has previously been observed in less dense ceramics and tentatively attributed to a phase transformation. The pressure dependences of both mode velocities for dense YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} ceramic show a pronounced change of slope at a pressure P{sub c}. For pressures below and above P{sub c} the pressure dependence of ultrasonic velocity is essentially linear. Above the knee, the enormous pressure dependences of the longitudinal mode velocity and hence of the bulk modulus persist. The temperature dependences of pressure derivatives of elastic stiffnesses and bulk modulus have been measured between 250 K and 295 K. The pressure P{sub c} at which the kink occurs decreases almost linearly with decreasing temperature and extrapolates to atmospheric pressure at about 220 K.
Date: December 1991
Creator: Cankurtaran, M.; Saunders, G. A.; Goretta, K. C. & Poeppel, R. B.
Partner: UNT Libraries Government Documents Department

Creep in electronic ceramics

Description: High-temperature creep measurements combined with microstructural investigations can be used to elucidate deformation mechanisms that can be related to the diffusion kinetics and defect chemistry of the minority species. This paper will review the theoretical basis for this correlation and illustrate it with examples from some important electronic ceramics having a perovskite structure. Recent results on BaTiO{sub 3}, (La{sub 1{minus}x}Sr){sub 1{minus}y}MnO{sub 3+{delta}}, YBa{sub 2}Cu{sub 3}O{sub x}, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}, (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and Sr(Fe,Co){sub 1.5}O{sub x} will be presented.
Date: April 27, 2000
Creator: Routbort, J. L.; Goretta, K. C. & Arellano-Lopez, A. R.
Partner: UNT Libraries Government Documents Department

Search for small-angle neutron scattering in MnO at 1700K

Description: A preliminary small-angle scattering (SANS) experiment has been performed on MnO single crystal at the Intense Pulsed Neutron Source. The experiment was preformed at 1700/sup 0/K at oxygen partial pressures of 2.2 x 10/sup -4/, 1 x 10/sup 2/, and 2 x 10/sup 2/ Pa, which resulted in deviations from stoichiometry of about 0.0015, 0.082, and 0.127. No statistically significant change in SANS was observed at this temperature with the pressure changes. Neither was any significant change observed in the wavelength-dependent sample transmission, also measured in-situ as a function of pressure. Therefore, either clustering of cation vacancies is negligible in MnO for these conditions, or the clusters are smaller than about 5 A. Of proposed cluster configurations, only the existence of the smallest (4:1, 6:2, or possible 8:3) appears to be consistent with these results.
Date: 1986
Creator: Routbort, J. L.; Epperson, J. E.; Klippert, T. E. & Goretta, K. C.
Partner: UNT Libraries Government Documents Department

Deformation of nonstoichiometric CuO polycrystals

Description: The current interest in fabrication methods for high temperature superconductors has fostered heightened interest in the precursor materials. It has been shown that the reaction kinetics for formation of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}, (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and YBa{sub 2}Cu{sub 3}O{sub x} are related to the copper oxide precursor through both the size of the starting powder and the oxidation state, with finer CuO powders reacting faster. Many proposed fabrication methods include a high temperature mechanical working step during the reaction process. However, little is known about the diffusional and mechanical properties of CuO at the fabrication temperatures of interest. The literature indicates only that the electrical conductivity of CuO is independent of the oxygen partial pressure (PO{sub 2}). Therefore, only intrinsic ionization occurs for CuO. Thus, for a given temperature, the concentrations of electrons and holes are fixed. In this study, compression creep was employed to shed light upon the diffusion of rate-controlling defects in nonstoichiometric CuO. Tests were performed on polycrystalline samples over a range of temperature (T), PO{sub 2}, and strain rate ({epsilon}). Data were analyzed with standard equations for steady-state creep. Electron microscopy was used in conjunction with the data analysis to identify the operative creep mechanisms. These results for CuO will be contrasted with previous work performed on another copper oxide compound, Cu{sub 2}O.
Date: July 1, 1994
Creator: Boling-Risser, M. A.; Goretta, K. C. & Routbort, J. L.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications. Annual report for FY 1993

Description: Development of useful high-critical-temperature superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes technical progress of research and development efforts aimed at producing superconducting components in the Y-Ba-Cu, (Bi,Pb)-Sr-Ca-Cu,(Tl,Pb, Bi)-(Ba,Sr)-Ca-Cu, and Hg-Ba-Ca-Cu-O oxide systems. Topics discussed are synthesis and heat treatment of high-T{sub c} superconductors; formation of monolithic and composite wires, tapes, and coils, characterization of structures and superconducting and mechanical properties; fabrication and properties of films; and development of properties of films; and development of prototype components. Collaborations with industry and academia are documented.
Date: October 1, 1993
Creator: Poeppel, R. B.; Goretta, K. C. & Askew, T. R.
Partner: UNT Libraries Government Documents Department

Effects of Bi and Bi{sub 2}O{sub 3} additions on the microstructure and superconducting properties of powder-in-tube BSCCO (2212) tapes

Description: The microstructural development and superconducting properties of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} (Bi-2212) Agclad powder-in-tube tapes with 2 vol% bismuth (Bi) added from either Bi (s) or Bi{sub 2}O{sub 3} powders were investigated. Such additives reduce the peritectic decomposition temperature of pure Bi-2212 by approximately 15-20{approximately}C. Scanning electron microscopy (SEM) and optical microscopy on polished top and cross-sections revealed that the volume fraction of Bi-free phases was lower in the Bi-added specimens relative to those based on pore Bi-2212. In addition, it appeared that the Bi-added samples had improved grain alignment, which was confirmed by x-ray diffraction analysis. Magnetic hysteresis (at 5 K between {+-} 5.5 T) and transport measurements (at 4.2 K) were performed on each specimen. These results showed that Bi-additions yielded superior magnetization critical currents, which is attributed to improved grain alignment and reduced secondary phases.
Date: October 1, 1994
Creator: Guo, J.; Lewis, J. A. & Goretta, K. C.
Partner: UNT Libraries Government Documents Department

Characterization of hot isostatically pressed Bi-Sr-Ca-Cu-O as a function of consolidation variables

Description: Fully dense, bulk Bi{sub 2}Sr{sub 1.7}CaCu{sub 2}O{sub x} (2212) superconductor pellets were made by hot isostatic pressing in an inert atmosphere. Electron microscopy revealed that rotation and bending of the platelike 2212 grains were responsible for much of the densification. Under processing conditions of 825{degrees}C and 105 MPa, dense pellets were obtained in 15 min. Many dislocations, planar faults, and, perhaps, intergrowths of the Bi{sub 2}Sr{sub 2}CuO{sub x} phase were produced during pressing. The dislocations were largely present in subgrain boundaries when the pressing times were increased to 45--120 min.
Date: November 1, 1991
Creator: Goretta, K. C.; Miller, D. J.; Poeppel, R. B. & Nash, A. S.
Partner: UNT Libraries Government Documents Department

Processing and fabrication of high-{Tc} superconductors for electric power applications

Description: Recent developments in the powder-in-tube fabrication of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} tapes include identification of high current transport regions of the superconductor core, optimization of conductor design and processing to take advantage of these high current regions, optimization of superconductor powders and heat treatments, and incorporation of flux pinning defects into the superconductor grains. These developments are briefly discussed and their implications are assessed.
Date: September 1997
Creator: Balachandran, U.; Iyer, A. N.; Goretta, K. C. & Haldar, P.
Partner: UNT Libraries Government Documents Department

Hardness and microstructure of internally oxidized silver alloys

Description: Alloys of Ag, Ag/1.12 at.% Mg, and Ag/0.25 at.% Mg-0.25 at.% Ni were internally oxidized at 450 to 825 C and their hardnesses and microstructure were observed. Microhardness profiles showed that hardness was high near the surface and decreased with depth into the sample. Microstructure contained regions of small and large grains, where region sizes were dependent on treatment temperature. Transitions between small- and large-grained regions were abrupt. Treatments at higher temperatures failed to alter grain structure, indicating that Mg-O clusters had indeed pinned the grain boundaries. Clustering was shown to affect the hardness of oxidized alloys, not only by inhibiting grain growth, but also by inhibiting dislocation motion.
Date: November 11, 1999
Creator: Prorok, B. C.; Park, J. H.; Goretta, K. C.; Balachandran, U. & McNallan, M. J.
Partner: UNT Libraries Government Documents Department

High-temperature internal oxidation of Ag/1.2at.% Mg and Ag/0.25at.% Mg-0.25at.% Ni.

Description: High-temperature oxygen diffusion and internal oxidation in Ag, Ag/1.2 at.% Mg (Ag-Mg), and Ag/0.25 at.% Mg-0.25 at.% Ni (Ag-Mg-Ni) have been studied, mostly in air and 8% O{sub 2}, at 450-835 C. The focus of the studies was on thermogravimetric analysis, microhardness tests, and optical and electron microscopy observations of grain growth and its inhibition by oxidation. The internal oxidation of both alloys exhibited nearly identical activation energies (0.81 eV for Ag-Mg and 0.83 eV for Ag-Mg-Ni) and rate constants. The maximum O content of both alloys was superstoichiometric (e.g., O/Mg > 1.0) and the maximum O/Mg ratios were higher at lower temperatures than at higher temperatures (e.g., 1.25 at 500 C and 1.05 at 800 C). Diffusion of O in pure Ag was {approx}60 times faster at 825 C and {approx}400 times faster at 500 C than internal oxidation of either of the Ag alloys. Grain growth of both alloys and of the Ag was quantified between 450-800 C and related to internal oxidation.
Date: September 8, 1999
Creator: Balachandran, U.; Goretta, K. C.; McNallan, M. J.; Park, J.-H. & Prorok, B. C.
Partner: UNT Libraries Government Documents Department

Processing and properties of hot-forged bulk superconductors

Description: (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (Bi-2223) and TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (Tl-1223) bars were hot forged in air at 820--850C. Final stresses of 2--3 MPa were sufficient to produce >95% dense Bi-2223 bars. In contrast, stresses to {approx}42 MPa were able to produce only 75--80% dense Tl-1223 bars. The Bi-2223 bars were more phase-pure and exhibited much stronger c-axis textures than the Tl-1223. Maximum critical current densities at 77 K were 8 {times} 10{sup 4} A/cm{sup 2} for the Bi-2223 and 2 {times} 10{sup 4}/cm{sup 2} for the Tl-1223. Fracture strength and toughness values were 140 MPa and 2.9 MPa{radical}m for the Bi-2223 and 50 MPa and 0.5 MPa{radical}m for the Tl-1223.
Date: December 31, 1995
Creator: Goretta, K.C.; Lanagan, M.T.; Picciolo, J.J.; Youngdahl, C.A.; Balachandran, U. & Chen, Nan
Partner: UNT Libraries Government Documents Department

Critical current densities in Bi-2223 sinter forgings.

Description: (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (Bi-2223) bars, prepared by sinter forging, exhibited good phase purity and strong textures with the c axes of the Bi-2223 grains parallel to the forging direction. The initial zero-field critical current density (J{sub c}) of the bars was 10{sup 3} A/cm{sup 2}, but because the forged bars were uncoated, this value decreased with repeated thermal cycling. J{sub c} as a function of applied magnetic field magnitude and direction roughly followed the dependencies exhibited by Ag-sheathed Bi-2223 tapes, but the forged bars were more strongly dependent on field strength and less strongly dependent on field angle.
Date: July 23, 1999
Creator: Balachandran, U.; Fisher, B. L.; Goretta, K. C.; Harris, N. C. & Murayama, N.
Partner: UNT Libraries Government Documents Department

Erosion of a geopolymer.

Description: Solid-particle erosion studies were conducted on a representative geopolymer. The test conditions were normal impact of 390-{micro}m angular Al{sub 2}O{sub 3} erodent particles moving at 50, 70, or 100 m/s. Steady-state erosion rates were obtained and the material-loss mechanism was studied by scanning electron microscopy. The geopolymer responded as a classic brittle material. Elastic-plastic indentation events led to formation of brittle cleavage cracks that resulted in spallation of material. The erosion rate was proportional to erodent velocity to the 2.3 power. The erosion rate and mechanism for the geopolymer were nearly identical to what has been observed for erosion of Si single crystals.
Date: July 2, 2002
Creator: Goretta, K. C.; Chen, N.; Routbort, J. L.; Lukey, G. C. & van Deventer, J. S. J.
Partner: UNT Libraries Government Documents Department

Mechanical properties and deformation of polycrystalline lithium orthosilicate

Description: Room-temperature strength, fracture toughness, Young's modulus, and thermal-shock resistance were determined for 68--98% dense lithium orthosilicate (Li/sub 4/SiO/sub 4/) specimens. In the low-density regime, both strength and fracture toughness were controlled by the density of the specimen. At high density, the strength depends on grain size. Young's modulus values ranged from 30--103 GPa at densities between 68 and 98% TD. A critical quenching temperature difference in the range of 150--170/degree/C was observed in thermal-shock tests of bar specimens. Steady-state creep tests indicated 90% dense Li/sub 4/SiO/sub 4/ fractures at T less than or equal to 800/degree/C before reaching steady state and deforms plastically at 900/degree/C. It is more creep-resistant at 900/degree/C than Li/sub 2/O, about equal to Li/sub 2/Zr)/sub 3/, and less than LiA10/sub 2/. 13 refs., 4 figs., 1 tab.
Date: February 1, 1988
Creator: Bar, K.; Chu, C.Y.; Singh, J.P.; Goretta, K.C.; Routbort, J.L.; Billone, M.C. et al.
Partner: UNT Libraries Government Documents Department

Flux pinning by 211 precipitates in melt-processed YBa{sub 2}Cu{sub 3}O{sub x}

Description: Magnetic hysteresis data have been taken at 4.2 and 50 K over a wide range of magnetic fields on melt-textured (MT) and quench-melt-growth-processed (QMGP) YBa{sub 2}Cu{sub 3}O{sub x} samples with 6 vol.% Of Y{sub 2}BaCuO{sub x} (211). In order to obtain accurate comparisons of the intragranular critical current densities, the magnetization measurements were performed on finely powdered samples, the average particle size of which was less than the grain size of the original sample. The QMGP samples exhibited substantially larger hysteresis, indicating significantly enhanced flux pinning at these temperatures. At 4.2 K and 5 T, J{sub c} increase from 4 {times} 10{sup 4} A/cm{sub 2} in the MT sample to 5.5 {times} 10{sup 5} A/cm{sup 2} in the QMGP sample. A possible pinning mechanism related to the observed hysteretic behavior is discussed.
Date: August 1, 1992
Creator: Shi, D.; Sengupta, S.; Smith, M.; Wang, Z.; Biondo, A. C.; Balachandran, U. et al.
Partner: UNT Libraries Government Documents Department