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in subjects: "Barium Compounds"

open access

Microwave characterization of high-temperature superconductors

Thick (10-15 {mu}m) Tl-Ba-Ca-Cu-O films have been deposited onto yttria-stabilized zirconia and Ag substrates by d.c. magnetron sputtering techniques. Direct deposition onto 1'' diameter yttria-stabilized zirconia yields films with typical 22 GHz surface resistance (R{sub s}) values of 5.2 {plus minus} 2 m{Omega} and 52 {plus minus} 2 m{Omega} at 10 K and 77 K, respectively. For comparison, R{sub s} of Cu at this same frequency is 10 m{Omega} at 4 K and 22 m{Omega} at 77 K. Tl-Ba-Ca-Cu-O films … more

Date: January 1, 1989

Creator: Cooke, D. W.; Gray, E. R.; Arendt, P. N.; Beery, J. G.; Bennett, B. L.; Brown, D. R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Scrubbing of iodine from gas streams with mercuric nitrate-conversion of mercuric iodate product to barium iodate for fixation in concrete

A bench-scale model of a mercuric nitrate scrubber for removal of iodine from off-gas streams was constructed and operated in conjunction with a mercuric iodate-to-barium iodate conversion system to determine the feasibility of total recycle of all processing solutions. The two main aspects of the system examined were (1) the extent of contamination of the barium iodate product, and (2) the effect of cross-contamination of various process solutions on the efficiency of the process. The experime… more

Date: June 1, 1980

Creator: Rogers, G. C.; Moore, J. G. & Morgan, M. T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

High Resolution-Angle Resolved Photoemission Studies of High Temperature Superconductors

Recent photoemission studies of Y 123 and Bi 2212 performed with high energy and angular resolution have provided detailed information on the nature of the states near the Fermi level. Measurements of the superconducting gap, band dispersion, and the density of states near the Fermi level in the normal state all support a Fermi liquid description of these materials. 5 refs., 4 figs.

Date: August 1, 1989

Creator: Olson, C. G.; Liu, R.; Lynch, D. W.; Veal, B. W.; Chang, Y. C.; Jiang, P. Z. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Reaction of metal sulfates with molybdenum oxide, a high temperature reaction step for thermochemical cycles

The reaction of sulfates with molybdenum oxide at high temperature was studied to determine the feasibility of using these reactions in a thermochemical process for making hydrogen. The experiments were performed by heating the blended powders to temperatures of 1075 K and higher and analyzing the evolved gas for acid content. It was found that the reaction rate over the first few minutes increased with both temperature and MoO/sub 3/. The fraction of sulfate reacting in the first 5 minutes var… more

Date: January 1, 1980

Creator: Hollabaugh, C. M.; Wallace, T. C.; Bowman, M. G. & Jones, W. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Magnetic hysteresis and relaxation in Ag-sheathed TlBaCaCuO (1223) and Bi(Pb)SrCaCuO (2223) superconducting tapes

Magnetic hysteresis (7--75 K in magnetic fields up to 5 T) and relaxation characteristics (5--50 K in magnetic fields up to 2 T) have been measured with the field perpendicular to the surface of Ag-sheathed TlBaCaCuO (1223 phase) and Bi(Pb)SrCaCuO (2223 phase) superconducting tapes. A study of the difference in the magnetic hysteresis between precursor powders and as-processed tapes was also carried out. The relaxation data were curve-fit using a rate equation for thermally activated flux motio… more

Date: January 1, 1992

Creator: Kung, P. J.; Maley, M. P.; Coulter, J. Y.; Willis, J. O.; Peterson, D. E.; McHenry, M. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fine scale mesostructures in superconducting and other materials

We review experimental and theoretical literature on mesoscale features and structures in a variety of displacively transforming materials. These include twinning in martensites and the much finer scale tweed; both may have significant effects on both normal and superconducting properties. Elastic properties are particularly strongly affected. Recent x-ray neutron experiments suggest them in hi-{Tc} materials.

Date: January 1, 1992

Creator: Krumhansl, J.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Anisotropic shift of the irreversibility line by neutron irradiation

The irreversibility line of high-{Tc} superconductors is shifted considerably by irradiating the material with fast neutrons. The anisotropic and non-monotonous shift is qualitatively explained by a simple model based on an interaction between three pinning mechanisms, the intrinsic pinning by the ab-planes, the weak pinning by the pre-irradiation defect structure, and strong pinning by neutron induced defect cascades. A correlation between the cascade density and the position of the irreversib… more

Date: September 1, 1991

Creator: Sauerzopf, F.M.; Wiesinger, H.P.; Weber, H.W. (Atominstitut der Oesterreichischen Universitaeten, Vienna (Austria)); Crabtree, G.W.; Frischherz, M.C. & Kirk, M.A. (Argonne National Lab., IL (United States))

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Sequential purification and crystal growth for the production of low cost silicon substrates. Quarterly technical progress report No. 2, 1 January 1980-31 March 1980

The objective of this program is to identify and develop low cost processing for fabricating large grain size polycrystalline silicon substrates. Metallurgical grade silicon (MG-Si) which is low cost and abundant for industrial usage was chosen as starting material. However, MG-Si cannot be used directly as substrates for solar cell fabrication; the further purification and recrystallization of MG-Si are needed. The conventional method of purifying MG-Si requires the conversion of Si to gaseous… more

Date: May 1, 1980

Creator: Liaw, M. & D'Aragona, F.S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Oxygen ordering and strain-related morphology in YBa sub 2 Cu sub 3- x O sub 7 systems

Monte Carlo simulations were performed on an anisotropic lattice gas model which represent well the interactions between oxygen atoms in YBa{sub 2}Cu{sub 3}O{sub 7} systems doped with trivalent impurity atoms M such as Fe or Al. Concentration wave amplitudes obtained from these simulations were used to calculate the diffuse X-ray scattering intensity caused by the resulting displacement field using a concentration wave/displacement wave approach, and the results are compared with X-ray and elec… more

Date: January 1, 1992

Creator: Cha, Zhi-Xiong; Zhu, Yimei & Welch, D.O.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The EPRI Laboratory experiments at ANL. [Vaporization of core-concrete mixtures]

The vaporization of core-concrete mixtures is being measured using a transpiration method. Mixtures of stainless steel, concrete (limestone or basaltic) and urania (doped with La/sub 2/O/sub 3/, SrO, BaO, and ZrO/sub 2/) are vaporized at 2150 - 2400 K from a zirconia crucible into flowing He - 6% H/sub 2/ gas. Up to 600 ppM H/sub 2/O is added to the gas to fix the partial molar free energy of oxygen in the range -420 kJ to -550 kJ. The fraction of the sample that is vaporized is determined by w… more

Date: October 28, 1987

Creator: Roche, M. F.; Settle, J. L.; Leibowitz, L.; Johnson, C. E. & Ritzman, R. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Rotational magnetic processes in YB sub 2 Cu sub 3 O sub 7

A polycrystalline superconducting thin-disk sample was rotated in a fixed field ({rvec H}) at 4.2 K, and the vector magnitude and orientation of the total magnetization ({rvec M}) were measured as the sample-rotation angle ({Theta}) was slowly cycled between 0 and 360{degree}. The measured {rvec M} was decomposed into a penetrating (vortex) flux component {rvec M}{sub p} that rotates rigidly with the sample at very small {Theta} and a diamagnetic (shielding) component {rvec M}{sub d} that stays… more

Date: January 1, 1989

Creator: Liu, Liwen; Kouvel, J.S.; Brun, T.O. (Illinois Univ., Chicago, IL (USA). Dept. of Physics & Argonne National Lab., IL (USA))

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Mechanical after-effect studies of oxygen relaxation in YBa sub 2 Cu sub 3 O sub 7-. delta

YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} has an anelastic relaxation involving motion of an oxygen atom or defect. This relaxation has been studied with good agreement by more than seven investigating teams over the temperature range from 200 to 550{degrees}C using internal friction techniques. We have extended measurements of this relaxation to a new regime of temperature and relaxation time using the mechanical after-effect method. Our results cover an additional three orders of magnitude in… more

Date: January 1, 1991

Creator: Cost, J.R. (Los Alamos National Lab., NM (United States)) & Stanley, J.T. (Arizona State Univ., Tempe, AZ (United States))

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Reflectance of Co- and Nb-doped BaTiO/sub 3/ for photon energies from 1. 8 to 70 eV

The reflectance spectra of Co- and Nb-doped BaTiO/sub 3/ crystals have been measured for photon energies from 1.8 to 70 eV. For both types of crystal, structures observed in the 1.8 to 2.3 eV range can be attributed to the presence of residual impurities. Between 2.3 and 3.2 eV the peaks in the reflectance of the Co-doped crystal are found to be of an acceptor charge transfer type. For Nb-doped crystals structures appear at the bottom of the conduction band. For energies larger than 3.2 eV the … more

Date: January 1, 1985

Creator: Goudonnet, J.P.; Godefroy, G.; Inagaki, T.; Moretti, P.; Williams, M.W. & Arakawa, E.T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High-Energy Neutron Spectroscopy on F-Electron Oxides

Neutron inelastic scattering with the chopper spectrometers at IPNS has been used to measure, for the first time, the ground to excited crystal-field transitions in PrO/sub 2/ (130 meV), BaPrO/sub 3/ (255 meV), and UO/sub 2/ (approx.160 meV). From these measurements we deduce the values of V/sub 4/ = A/sub 4/ (r/sup 4/) and compare both the absolute values and their variation with theoretical estimates. In the case of UO/sub 2/ two peaks are seen, one at 155 and the other at 172 meV. This struc… more

Date: January 1, 1985

Creator: Kern, S.; Loong, C.K. & Lander, G.H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Preparation and properties of evaporated CdTe films compared with single-crystal CdTe. Progress report no. 6, February 1, 1982-April 30, 1982

Films of n-type CdTe:In have been deposited by hot-wall vacuum evaporation (HWVE) on 7059 glass substrates, BaF/sub 2/ single crystal substrates, metal (Pt, Cr, Mo, Al) coated glass substrates, and single crystal p-type CdTe substrates. Films deposited on 7059 glass show typically a dark resistivity of 2 x 10/sup 5/ ohm-cm and a light resistivity of 3 x 10/sup 2/ ohm-cm. With increasing In source temperature, the resistivity decreases, but actually increases slightly again if the T/sub In/ is r… more

Date: January 1, 1982

Creator: Bube, R H

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Superconducting materials

Our research on high temperatures superconductors has produced novel insights for the normal state properties of copper oxides that have been discovered in the last few years. Advances in materials preparation have produced singly crystal samples, and sophisticated surface cleavage techniques have unveiled truly metallic behavior in many respects. Thus, the recent confirmation of a Fermi surface in several cuprate superconductors by photoemission spectroscopy has aroused interest in experimenta… more

Date: January 1, 1992

Creator: Ruvalds, J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Electronic structure of monoclinic BaBiO sub 3

We present the results of photoemission studies of valence disordered'' monoclinic BaBiO{sub 3} in the photon energy range 15--120 eV. The line-shapes of the valence band photoemission spectra and the Ba contributions to the valence band are very similar to the line shapes of the total density of states and Ba partial density of states, respectively. Oxygen resonance is observed, demonstrating the existence of empty O 2p states. These results support a more covalent rather than a simple ionic p… more

Date: January 1, 1989

Creator: Shen, Z. X.; Lindberg, P. A. P.; Wells, B. O.; Dessau, D. S.; Borg, A.; Lindau, I. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Neutron scattering studies of spin correlations in metallic YBa sub 2 Cu sub 3 O sub 6+x

Electron-electron correlations appear to play an important role in determining many properties of the copper oxide superconductors. One significant consequence of the electronic coulomb interactions are spin correlations. In the insulating phases of the layered cuprates, where the antibonding band due to Cu 3d{sub x}{sup 2} {minus} {sub y}{sup 2}-O 2p{sub {sigma}} hybridization in the CuO{sub 2} planes is half filled, long-range antiferromagnetic order is observed. As the layers are doped with … more

Date: January 1, 1991

Creator: Tranquada, J.M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Intergranular and interphase boundaries in ceramics

Interfaces are of great importance in both electronic and structural ceramics. The microstructure and microchemistry of interfaces can be studied by transmission electron microscopy, both high resolution and analytical. Examples are taken from both intergranular and interphase boundaries in ceramics. The former include low angle, twin and 90/degree/ boundaries in YBa/sub 2/Cu/sub 3/O/sub 7/ superconductors. Interphase boundaries include epitactic layers of YBa/sub 2/Cu/sub 3/O/sub 7/on SrTiO/su… more

Date: January 1, 1989

Creator: Mitchell, T.E.; Roy, T. & Unal, O.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Influence of oxygen partial pressure and silver additions on microstructure and related properties of YBCO superconductors

Microstructure has a great influence on the mechanical and superconducting properties of YBCO. Mechanical properties of YBCO can be improved by both modifying the monolithic microstructure and developing composites of YBCO with silver (Ag). When monolithic YBCO was sintered to high densities ({approx} 91%) at a relatively low temperature ({approx} 910{degrees}C) by controlling oxygen partial pressure during sintering, the result was a small-grain microstructure (average grain size {approx} 5 {m… more

Date: February 1, 1992

Creator: Singh, J.P.; Joo, J.; Guttschow, R. & Poeppel, R.B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Phase separation of holes in antiferromagnets

It is shown that dilute holes in an antiferromagnet are unstable against phase separation into a hole-rich phase and a no-hole phase. When the spin exchange interaction J exceeds a critical value J{sub c}, one phase consists of all holes, the other all electrons. The argument is presented in detail for the t--J model but evidence of phase separation in other models is mentioned. 11 refs.

Date: January 1, 1989

Creator: Emery, V.J.; Kivelson, S.A.; Lin, H.Q. (Brookhaven National Lab., Upton, NY (USA); California Univ., Los Angeles, CA (USA). Dept. of Physics & Brookhaven National Lab., Upton, NY (USA))

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

(Thermochemistry of phases related to oxide superconductors)

The aim of this project has been to understand the crystal-chemical and energetic constraints on the stability of phases related to oxide superconductors, using high temperature reaction calorimetry, the unique expertise of this laboratory, coupled with synthesis and structural studies. The YBCO (Y{sub 2}O{sub 3}-BaO-Cu-O) system has been studied in detail by Zhou for his Ph.D. thesis, while DiCarlo has been studying alkaline earth doped lanthanium cuprates of the series La{sub 2-x}A{sub x}CuO{… more

Date: January 1, 1991

Item Type: Report

Partner: UNT Libraries Government Documents Department

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mu. SR investigation of magnetism and superconductivity in (Y sub 1-x Pr sub x )Ba sub 2 Cu sub 3 O sub 7

Muon spin rotation and relaxation techniques have been used to study the superconductivity and magnetism in (Y{sub 1-x}Pr{sub x})Ba{sub 2}Cu{sub 3}O{sub 7} (0{le}x{le}1) and PrBa{sub 2}Cu{sub 3}O{sub 6}. Clear evidence for magnetic ordering of the Cu moments within the Cu-O planes is seen. Additionally, a lower magnetic transition is observed which, based upon previous work, has been associated with the ordering of Pr moments on the Y sublattice of the YBa{sub 2}Cu{sub 3}O{sub 7} structure. For… more

Date: January 1, 1989

Creator: Cooke, D. W.; Kwok, R. S.; Jahan, M. S.; Lichti, R. L.; Adams, T. R.; Boekema, C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Positron-annihilation 2D-ACAR studies of disordered and defected alloys

Theoretical and experimental progess in connection with 2D-ACAR positron annihilation studies of ordered, disordered, and defected alloys is discussed. We present, in particular, some of the recent developments concerning the electronic structure of disordered alloys, and the work in the area of annihilation from positrons trapped at vacancy-type defects in metals and alloys. The electronic structure and properties of a number of compounds are also discussed briefly; we comment specifically on … more

Date: September 1, 1987

Creator: Bansil, A.; Prasad, R.; Smedskjaer, L. C.; Benedek, R. & Mijnarends, P. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department