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in subjects: "Barium Oxides"

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Array automated assembly: Phase 2. Quarterly report

An analysis was made of cost trade-offs for shaping modified square wafers from cylindrical crystals. For reasonably expectable silicon and sheet costs, the optimum shape will be nearer a circle than a square. Tests were conducted of the effectiveness of texture etching for removal of surface damage on sawed wafers. Four glass systems have survived preliminary screening tests for use as edge masking dielectrics. These include beta-spodumen, MgO-Al/sub 2/O/sub 3/ borosilicate, baria and titania … more

Date: February 1, 1978

Creator: Taylor, W.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Theoretical modeling and experimental characterization of planar defects in Y sub 2 Ba sub 4 Cu sub 6+x O sub 14+x

Crystallographic defects and phase transformations in the system Y{sub 2}Ba{sub 4}Cu{sub 6 + x}O{sub 14 + x}(0{le}{times}{le}4) are investigated by high resolution transmission electron microscopy (TEM) and static lattice, three dimensional Monte Carlo computer simulations. High resolution images of partially transformed (x = 2 to x = 1) material reveal a prevalence of CuO planar defects (stacking faults) associated with the transformation and an absence of disturbance to the perovskite Ba-Y-Ba… more

Date: November 1, 1990

Creator: Burmester, C. P.; Fendorf, M.; Gronsky, R. & Wille, L. T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The use of BaF sub 2 buffer layers for the sputter-deposition of TlCaBaCuO thin-film superconductors

Thin films of the Tl-based superconductors often have relatively poor properties because of film/substrate interdiffusion which occurs during the anneal. We have therefore investigated the use of BaF{sub 2} as a diffusion barrier. TlCaBaCuO thin films were deposited by dc magnetron sputtering onto MgO <100> substrates, both with and without an evaporation-deposited BaF{sub 2} buffer layer, and post-annealed in a Tl over-pressure. Electrical properties of the films were determined by four-point … more

Date: January 1, 1989

Creator: Hubbard, K. M.; Arendt, P. N.; Brown, D. R.; Cooke, D. W.; Elliott, N. E.; Farr, J. D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Laser deposition and laser modification of high-temperature superconducting thin films

Applications of high-temperature superconductors (HTSC) may require epitaxial films with {Tc}{ge}77 K, and J{sub c}{ge}10{sup 6} A/cm{sup 2}. In situ pulsed laser deposition (PLD) is suitable for fabrication of such films. We report parametric studies on the effect of laser and processing parameters on the crystallinity, epitaxy and electrical properties of laser-deposited HTSC thin films. In addition, several laser-based processes were used to modify the electrical properties ({Tc} and J{sub c… more

Date: January 1, 1991

Creator: Dye, R. C.; Foltyn, S. R.; Nogar, N. S.; Wu, X. D.; Peterson, E. J. & Muenchausen, R. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The influence of anharmonic phonons on the isotope effect in high- Tc oxides

Anharmonic phonons are examined to study the unusual isotope effect exponents for the high-{Tc} oxides. Within a simple model of anharmonicity, the mass dependences of the electron-phonon coupling constant {lambda} and the phonon frequency determine the isotope effect exponent {alpha} as a function of coupling strength. A model in which the outer wells of a multiple-well potential deepen as the orthorhombic/low temperature tetragonal phase transition in La{sub 2-x}M{sub x}CuO{sub 4} is approach… more

Date: January 1, 1992

Creator: Crespi, V.H. & Cohen, M.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Recent advances in high-temperature superconductor wire fabrication and applications development

In this paper, recent advances in fabrication of HTS wires are summarized, and detailed discussion is provided for developments in near- and intermediate-term applications. Near-term applications, using presently obtainable current densities, include: liquid-nitrogen depth sensors, cryostat current leads, and magnetic bearings. Intermediate-term applications, using current densities expected to be available in the near future include fault-current limiters and short transmission lines. 25 refs.

Date: January 1, 1992

Creator: Hull, J.R. & Uherka, K.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Electron irradiation effects in YBa/sub 2/Cu/sub 3/O/sub 7-delta/ single crystals

Defect structures in YBa/sub 2/Cu/sub 3/O/sub 7/minus/delta/ produced by electron irradiation at 300/degree/K, were investigated by transmission electron microscopy. Threshold energies for the production of visible defects were determined to b 152 keV and 131 keV (+- 7 keV) in directions near the a- and b-axes, respectively (b > a, both perpendicular to c, the long axis in the orthorhombic structure). During above-threshold irradiations in an electron flux of 3 x 10 /sup 18/ cm/sup /minus/2/s/s… more

Date: April 1, 1988

Creator: Kirk, M.A.; Baker, M.C.; Liu, J.Z.; Lam, D.J. & Weber, H.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Chemical Processing Technology Quarterly Progress Report, October-December 1961

The ICPP processed Al fuel, prtncipally of the MTR-ETR type, durtng this quarter. Newly designed and installed processing equipment exhibited excellent operating performance. This included direct-air-pulsed extraction, stripping and scrub columns, and a cascade-controlled continuous evaporator in first cycle product concentration service. Aqueous zirconium fuel processing studies continued with the objective of adapting the hydrofluoric acid process to continuous dissolution-complexing to incre… more

Date: March 28, 1962

Creator: Bower, J. R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Preparation of oxide superconductors

Preparation of bulk superconductors by cold pressing and sintering of metal oxides has been optimized in this study. A knowledge of phase behavior was used in developing a flux method for growing superconducting single crystals of yttrium and gadolinium based superconductors. Means of achieving single-phase, high-density samples of (Rare Earth)-Ba/sub 2/Cu/sub 3/O/sub 7/ with optimal electronic properties are reviewed. 2 refs., 2 figs.

Date: January 1, 1988

Creator: Peterson, D.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Energetics and statistics of order in alloys with application to oxide superconductors

Now that first-principles calculations of ordering transformations are becoming increasingly accurate, the deficiencies of earlier mean field methods are becoming increasingly apparent. New techniques, based on cluster expansions, are now alleviating many of the earlier problems and are producing very satisfactory results. These ideas will be illustrated for the case of oxygen ordering in the YBa{sub 2}Cu{sub 3}O{sub z} superconducting compound, for which a very simple two-dimensional Ising mod… more

Date: June 1, 1991

Creator: de Fontaine, D. (Lawrence Livermore National Lab., CA (United States) California Univ., Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering); Ceder, G. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Materials Science and Engineering) & Asta, M. (Lawrence Livermore National Lab., CA (United States) California Univ., Berkeley, CA (United States).

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Study of selected off-gases produced during the immobilization of nuclear wastes in the SYNROC process. Final report for year ended December 31, 1981. [Pollucite, CsAlSi/sub 2/O/sub 6/, and barium-cesium hollandite, (Ba,Cs)Al/sub 2/Ti/sub 6/O/sub 16/]

Calculation of possible off-gases expected during the fabrication of SYNROC showed that volatilization of cesium would be a significant problem. Samples of the cesium containing minerals pollucite, CsAlSi/sub 2/O/sub 6/, and barium-cesium hollandite, (Ba,Cs)Al/sub 2/Ti/sub 6/O/sub 16/, were prepared for vaporization studies. Fifteen vaporization runs were made with the hollandite samples. With dry air as the carrier gas, the vapor pressure of cesium over Ba/sub 0/ /sub 8/Cs/sub 0/ /sub 4/Al/sub… more

Date: December 31, 1981

Creator: Carpenter, J.H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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YBa sub 2 Cu sub (3-x) Co sub x O sub y : A substrate material for YBCO superconductors

The physical properties of the ceramic YBa{sub 2}Cu{sub (3-x)}Co{sub x}O{sub y} have been investigated in order to evaluate its usefulness as a substrate material for YBCO superconductors. YBa{sub 2}Cu{sub (3-x)}Co{sub x}O{sub y} has been found to be thermally and chemically compatible with 123 and displays adequate electrical properties for a substrate material. A material with the nominal composition of YBa{sub 2}Cu{sub 2.2}Co{sub 0.8}O{sub 7} was investigated, extensively. The mechanical pro… more

Date: April 1, 1992

Creator: Vienna, J.D.; Balachandran, U.; Poeppel, R.B. (Argonne National Lab., IL (United States)); Cermignani, W. & Taylor, J.A. (State Univ. of New York, Alfred, NY (United States). Coll. of Ceramics)

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Neutron scattering from the flux lattice in high temperature superconductors

Neutron scattering has been used to observe diffraction from the flux-line lattice in high temperature superconductors. This technique is particularly useful in such systems as it allows observations to be made over a wide range of temperature and magnetic field. Experiments on the systems K{sub 0.4}Ba{sub 0.6}BiO{sub 3} and YBa{sub 2}Cu{sub 3}O{sub 7--8} will be described with applied magnetic fields of up to 4 Tesla and for temperatures from 2K to {Tc}.

Date: January 1, 1991

Creator: Paul, D.McK. (Warwick Univ., Coventry (United Kingdom). Dept. of Physics); Forgan, E.M.; Cubitt, R.; Lee, S.L. (Birmingham Univ. (United Kingdom)); Mook, H.A. (Oak Ridge National Lab., TN (United States)) & Timmins, P. (Institut Laue-Langevin, 38 - Grenoble (France))

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Defect structures in YBa/sub 2/Cu/sub 3/O/sub 7-x/ produced by electron irradiation

Defect structures in YBa/sub 2/Cu/sub 3/O/sub 7-x/ produced by electron irradiation at 300/sup 0/ K were investigated by transmission electron microscopy. Threshold energies for the production of visible defects were determined to be 152 keV and 131 keV (+- 7 keV) in directions near the a and b (b > a) axes (both perpendicular to c, the long axis in the orthorhombic structure), respectively. During above threshold irradiations in an electron flux of 3 x 10/sup 18/ cm/sup -2/ s/sup -1/, extended… more

Date: December 1, 1987

Creator: Kirk, M.A.; Baker, M.C.; Liu, J.Z.; Lam, D.J. & Weber, H.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Anisotropy of oxygen tracer diffusion in YBa sub 2 Cu sub 3 O sub 7-. delta. single crystals

The crystal structure of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} strongly suggests that the diffusion of oxygen in this material will be highly anisotropic, with diffusion in the ab plane being much faster than diffusion parallel to the c axis, and this has been assumed in most analyses of diffusion in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}. The present data confirm this hypothesis; the diffusion coefficient in the ab plane is several orders of magnitude greater than the diffusion coefficient along th… more

Date: September 1, 1989

Creator: Rothman, S. J.; Routbort, J. L.; Liu, J.-Z.; Downey, J. W.; Thompson, L. J.; Fang, Y. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Electron beam induced oxygen in YBa sub 2 Cu sub 3 O sub 7-x superconductors

Thin foils of bulk YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) superconductors were subjected to electron irradiation in a Transmission Electron Microscope (TEM). The resulting disordering of the oxygen atoms and vacancies in the Cu-O planes was monitored by measuring the splitting of the (110) diffraction spots in the (001) diffraction pattern. Samples were irradiated at 83K with 100, 150, 200 and 300kV electrons. The 100kV electrons did not cause any disordering, even after prolonged irradiation. Th… more

Date: January 1, 1989

Creator: Basu, S.N.; Roy, T.; Mitchell, T.E. & Nastasi, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Non-stoichiometric defects in YBaCuO thin films

Defects in superconducting YBaCuO thin films deposited by laser ablation are investigated by high resolution transmission electron microscopy. Micrographs reveal numerous defects in the YBaCuO film, falling into four basic classes. One of these is an interesting, non-stoichiometric helical defect structure which possibly corresponds to a growth-related screw dislocation. In general, defects in the YBaCuO film are associated both with growth geometry and with local deviations in stoichiometry. S… more

Date: April 1, 1991

Creator: Fendorf, M.; Tidjani, M.; Burmester, C.; Gronsky, R. (Lawrence Berkeley Lab., CA (United States)) & Wille, L. (Florida Atlantic Univ., Boca Raton, FL (United States). Dept. of Physics)

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Formation and characterization of fission-product aerosols under postulated HTGR accident conditions

The paper presents the results of an experimental investigation on the formation mechanism and physical characterization of simulated nuclear aerosols that could likely be released during an HTGR core heat-up accident. Experiments were carried out in a high-temperature flow system consisting essentially of an inductively heated release source, a vapor deposition tube, and a filter assembly for collecting particulate matter. Simulated fission products Sr and Ba as oxides are separately impregnat… more

Date: July 1, 1982

Creator: Tang, I.N. & Munkelwitz, H.R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Computer modeling of Y-Ba-Cu-O thin film deposition and growth

The deposition and growth of epitaxial thin films of YBa{sub 2}Cu{sub 3}O{sub 7} are modeled by means of Monte Carlo simulations of the deposition and diffusion of Y, Ba, and Cu oxide particles. This complements existing experimental characterization techniques to allow the study of kinetic phenomena expected to play a dominant role in the inherently non-equilibrium thin film deposition process. Surface morphologies and defect structures obtained in the simulated films are found to closely rese… more

Date: July 1, 1991

Creator: Burmester, C.; Gronsky, R. (Lawrence Berkeley Lab., CA (United States)) & Wille, L. (Florida Atlantic Univ., Boca Raton, FL (United States). Dept. of Physics)

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Properties of epitaxial YBa sub 2 Cu sub 3 O sub 7-. delta. -based superconducting superlattices

Epitaxial YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting superlattices have been fabricated using pulsed laser deposition in which c-axis oriented YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} layers as thin as one unit cell thick are separated by relatively thick PrBa{sub 2}Cu{sub 3}O{sub 7-{delta}} based barrier layers. The superlattice {Tc} (R=0) decreases rapidly with increasing barrier layer thickness, but then saturates at a finite {Tc} for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} layers as thin as… more

Date: September 1, 1991

Creator: Norton, D.P.; Lowndes, D.H.; Zheng, Z. Y.; Feenstra, R. (Oak Ridge National Lab., TN (United States)) & Zhu, Shen (Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy)

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Extrusion of metal oxide superconducting wire, tube or ribbon

A process and apparatus for extruding a superconducting metal oxide composition YBa{sub 2}Cu{sub 3}O{sub 7-x} provides a wire (tube or ribbon) having a cohesive mass and a degree of flexibility together with enhanced electrical properties. Wire diameters in the range of 6--85 mils have been produced with smaller wires on the order of 10 mils in diameter exhibiting enhanced flexibility for forming braided, or multistrand, configurations for greater current carrying capacity. The composition for … more

Date: January 1, 1990

Creator: Dusek, J.T.

Item Type: Patent

Partner: UNT Libraries Government Documents Department

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Microstructure and properties of in-situ rf sputtered YBa sub 2 Cu sub 3 O sub 7 thin films for microwave applications

The residual surface resistance of a number of films of YBa{sub 2}Cu{sub 3}O{sub 7}, prepared by off-axis sputtering onto MgO substrates, has been measured using parallel-plate resonator technique. Deposition conditions were kept constant, apart from the substrate temperature. There is no correlation between surface resistance and other important microscopic parameters, such as T{sub c} and c-axis lattice parameter. There is, however, a trend to higher R{sub s} with increasing volume fraction o… more

Date: January 1, 1992

Creator: Reagor, D. W.; Houlton, R. J.; Garzon, F. H.; Hawley, M.; Raistrick, I. D. (Los Alamos National Lab., NM (United States)) & Piza, M. E. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Materials Science)

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Influence of ion beam mixing on the growth of high temperature oxide superconducting thin film

The superconducting properties of high temperature superconductor thin films are dependent on the quality of the substrate used to grow these films. In order to maximize the lattice matching between the superconducting film and the substrate, we have used a YBa{sub 2}Cu{sub 3}O{sub 7} thin film deposited on {l angle}100{r angle} SrTiO{sub 3} as a template. The first film was prepared by coevaporation of Y, BaF{sub 2} and Cu on {l angle}100{r angle} SrTiO{sub 3}, followed by an anneal in wet'' o… more

Date: January 1, 1989

Creator: Bordes, N.; Rollett, A.D.; Cohen, M.R. & Nastasi, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Grain boundary weak links in high- Tc superconductors

The transport critical current density (Jc) for high-{Tc} thin films, bicrystals, and bulk ceramics is shown to be determined by magnetic field penetration into the grain boundaries. The gross grain orientations may not in all cases be an important factor in determining this penetration. The parameter ({lambda}{sub G}/{lambda}{sub J}){sup 2} can characterize the strength of the grain boundary coupling, which depends mainly on the crystal coherence and connectivity at the boundary area.

Date: April 1, 1992

Creator: Shi, D.; Sengupta, S.; Goretta, K.C.; Salem-Sugui, S. Jr. (Argonne National Lab., IL (United States)); Smith, M. & Lwin, Y.N. (Western Illinois Univ., Macomb, IL (United States). Dept. of Physics)

Item Type: Article

Partner: UNT Libraries Government Documents Department