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in subjects: "Rare Earth Compounds"

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Electronic band structure and optical properties of the cubic, Sc, Y and La hydride systems

Electronic band structure calculations are used to interpret the optical spectra of the cubic Sc, Y and La hydride systems. Self-consistent band calculations of ScH/sub 2/ and YH/sub 2/ were carried out. The respective joint densities of states are computed and compared to the dielectric functions determined from the optical measurements. Additional calculations were performed in which the Fermi level or band gap energies are rigidly shifted by a small energy increment. These calculations are t… more

Date: January 1, 1980

Creator: Peterman, D. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Vapor phase spectroscopy of complex lanthanide halide--aluminum halide molecular species

The absorption spectrum of ErCl/sub 3/ (AlCl/sub 3/)/sub x/ vapor complex was measured and analyzed using the Judd-Ofelt theory. Structural correlations in other AlCl/sub 3/ vapor complexes and radiation emission are discussed. Fluorescence of TbCl/sub 3/ (AlCl/sub 3/)/sub x/ vapor complex and in the NdCl/sub 3/ (AlCl/sub 3/)/sub x/ system were studied. (DLC)

Date: January 1, 1977

Creator: Carnall, W T; Hessler, J P; Williams, C W & Hoekstra, H R

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Neutron diffraction study of magnetic order in the ternary superconductor ErMo/sub 6/Se/sub 8/

Synthesis of new classes of ternary superconducting materials has led to compounds which also show a strong tendency toward magnetic order when one of the constituent elements is a rare earth. Powder neutron diffraction data on superconducting (T/sub s/ approximately 6 K) samples of ErMo/sub 6/Se/sub 8/ taken in the temperature range 0.05 to 2.0 K show that magnetic Bragg peaks develop at T/sub M/ = 1.1 K, in agreement with specific heat studies. However, it is not possible to index these new r… more

Date: 1977~

Creator: Lynn, J. W.; Moncton, D. E.; Shirane, G.; Thomlinson, W.; Eckert, J. & Shelton, R. N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Elastic constants and the structural phase transition in La sub 2-x Sr sub x CuO sub 4

Resonant ultrasound spectroscopy is used to measure the temperature dependence of all six elastic moduli of La{sub 2-x}Sr{sub x}CuO{sub 4}. A giant softening (> 50% reduction) in the in-plane shear modulus, c{sub 66}, is observed and is attributed to the tetragonal-orthorhombic structural phase transition in this material. This phase transition and the corresponding softening is examined with a simple anharmonic mechanical model and a macroscopic Ginsburg-Landau formalism exploiting the full sy… more

Date: January 1, 1991

Creator: Sarrao, J.L.; Lei, Ming; Stekel, A.; Bell, T.M.; Leisure, R. G.; Sham, L.J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Techniques and processes for the measurement of the resonances of small single crystals

The mechanical resonances of small oriented single crystals of materials of interest to basic science and engineering can be used to determine all the elastic moduli and the ultrasonic attenuation of these materials. To measure the resonances of the samples without introducing the resonances of the measuring system requires that the transducers be non-resonant at the frequencies of interest, and that they be well isolated from their mounts. However, for samples near 1 mm in the largest dimensio… more

Date: January 1, 1991

Creator: Migliori, A.; Stekel, A.; Sarrao, J.L.; Visscher, W.M.; Bell, T. & Lei, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Development of improved cathodes for solid oxide fuel cells

The University of Missouri-Rolla conducted a 17 month research program focused on the development and evaluation of improved cathode materials for solid oxide fuel cells (SOFC). The objectives of this program were: (1) the development of cathode materials of improved stability in reducing environments; and (2) the development of cathode materials with improved electrical conductivity. The program was successful in identifying some potential candidate materials: Air sinterable (La,Ca)(Cr,Co)O{su… more

Date: March 1, 1991

Creator: Anderson, H.U.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Heat-Flux Gage thermophosphor system

This document describes the installation, hardware requirements, and application of the Heat-Flux Gage (Version 1.0) software package developed by the Oak Ridge National Laboratory, Applied Technology Division. The developed software is a single component of a thermographic phosphor-based temperature and heat-flux measurement system. The heat-flux transducer was developed by EG G Energy Measurements Systems and consists of a 1- by 1-in. polymethylpentene sheet coated on the front and back with … more

Date: August 1, 1991

Creator: Tobin, K.W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Static and dynamic spin fluctuations in the spin glass doping regime in La sub 2-x Sr sub x CuO sub 4+y

We review the results of neutron scattering studies of the static and dynamic spin fluctuations crystals of La{sub 2-x}Sr{sub x}CuO{sub 4+{delta}} in the doping regime intermediate between the Neel and superconducting regions. In this regime the in-plane resistance is linear in temperature down to {approximately}80 K with a crossover due to logarithmic conductance effects at lower temperatures. The static spin correlations are well-described by a simple model in which the inverse correlation le… more

Date: January 1, 1991

Creator: Birgeneau, R.J.; Belk, N.; Kastner, M.A.; Keimer, B. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Physics); Endoh, Y. (Tohoku Univ., Sendai (Japan). Dept. of Physics); Erwin, R.W. (National Inst. of Standards and Technology, Gaithersburg, MD (United States)) et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Assessment of U. S. domestic capacity for producing reactor-grade thorium dioxide and controlling associated wastes and effluents

Demand for reactor-grade ThO/sub 2/ is likely to increase as a result of the growing interest in the application of the thorium-uranium fuel cycle to nuclear reactors. The wastes and effluents identified with the production of ThO/sub 2/ from monazite sand are waste water, tailings, dust, smoke and gas, and radionuclides (primarily, /sup 232/Th and /sup 226/Ra). There are currently an estimated 1,500 short tons of crude thorium hydroxide byproduct that can be readily converted to reactor-grade … more

Date: February 1, 1978

Creator: Enderlin, W.I.

Item Type: Report

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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High temperature fuel cell research and development. Final technical status report, 1 March 1979-31 March 1980. [Molten carbonate fuel cells]

The objective of the program has been to evaluate potential materials for their chemical and physical stability in molten carbonate fuel cell electrolyte. Eleven powdered candidate materials were selected based on previous physical and chemical stability tests at elevated temperatures on solid materials and/or their thermodynamic stability with respect to proposed degradation reactions. The eleven candidate materials, plus gamma lithium aluminate, were characterized prior to corrosion testing u… more

Date: May 1, 1980

Creator: Lessing, P.A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Thulium-170 heat source

An isotopic heat source is formed using stacks of thin individual layers of a refractory isotopic fuel, preferably thulium oxide, alternating with layers of a low atomic weight diluent, preferably graphite. The graphite serves several functions: to act as a moderator during neutron irradiation, to minimize bremsstrahlung radiation, and to facilitate heat transfer. The fuel stacks are inserted into a heat block, which is encased in a sealed, insulated and shielded structural container. Heat pipe… more

Date: September 6, 1990

Creator: Walter, Carl E.; Van Konynenburg, Richard & VanSant, James H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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A toxicological study of gadolinium nitrate

The sensitization study in the guinea pig did not show gadolinium nitrate to have potential sensitizing properties. Skin application studies in the rabbit demonstrated that it was cutaneously a severe irritant. This material was considered an irritant in the rabbit eye application studies. 3 refs., 1 tab.

Date: May 1, 1988

Creator: London, J.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Incinerator ash dissolution model for the system: Plutonium, nitric acid and hydrofluoric acid

This research accomplished two goals. The first was to develop a computer program to simulate a cascade dissolver system. This program would be used to predict the bulk rate of dissolution in incinerator ash. The other goal was to verify the model in a single-stage dissolver system using Dy/sub 2/O/sub 3/. PuO/sub 2/ (and all of the species in the incinerator ash) was assumed to exist as spherical particles. A model was used to calculate the bulk rate of plutonium oxide dissolution using fluori… more

Date: June 1, 1988

Creator: Brown, E V

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Static magnetic ordering of CeCu/sub 2. 1/Si/sub 2/ found by muon spin relaxation

Zero- and longitudinal-field muon spin relaxation measurements on a poly-crystal sample of a heavy-fermion superconductor CeCu/sub 2.1/Si/sub 2/ (T/sub c/ = 0.7 K) have revealed an onset of static magnetic ordering below T )approximately) 0.8 K. The line shapes of the observed spectra in zero field indicate a wide distribution of static random local fields at muon sites, suggesting that the ordering is either spin glass or incommensurate spin-density-wave state. The observed width of the random… more

Date: January 1, 1988

Creator: Uemura, Y. J.; Kossler, W. J.; Yu, X. H.; Schone, H. E.; Kempton, J. R.; Stronach, C. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

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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Design, microstructure, and high-temperature behavior of silicon nitride sintered with rate-earth oxides

The processing-microstructure-property relations of silicon nitride ceramics sintered with rare-earth oxide additives have been investigated with the aim of improving their high-temperature behavior. The additions of the oxides of Y, Sm, Gd, Dy, Er, or Yb were compositionally controlled to tailor the intergranular phase. The resulting microstructure consisted of {beta}-Si{sub 3}N{sub 4} grains and a crystalline secondary phase of RE{sub 2}Si{sub 2}O{sub 7}, with a thin residual amorphous phase … more

Date: August 1, 1991

Creator: Ciniculk, M.K. (California Univ., Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering)

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Recovery of plutonium from HEPA filters by Ce(IV): promoted dissolution of PuO/sub 2/ and recycle of the cerium promoter

Studies carried out in this investigation included (1) electrolytic production of Ce(IV) from Ce(III), (2) leaching of refractory PuO/sub 2/ from HEPA filters with maintenance of Ce(IV) by anodic oxidation during leaching, and (3) evaluation of methods for contacting the HEPA solids with the leaching solution and for separating the solid residue from the leaching liquor. Anodic oxidation of Ce(III) was accomplished with an electric current efficiency of about 85% at current densities of 0.04 to… more

Date: May 1, 1980

Creator: Scheitlin, F.M. & Bond, W.D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Low temperature heat capacity of lutetium and lutetium hydrogen alloys

The heat capacity of high purity electrotransport refined lutetium was measured between 1 and 20/sup 0/K. Results for theta/sub D/ were in excellent agreement with theta values determined from elastic constant measurements. The heat capacity of a series of lutetium-hydrogen solid solution alloys was determined and results showed an increase in ..gamma.. from 8.2 to about 11.3 mJ/g-atom-K/sup 2/ for hydrogen content increasing from zero to about one atomic percent. Above one percent hydrogen ..g… more

Date: October 1, 1977

Creator: Thome, D. K.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

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Advances in materials science, Metals and Ceramics Division. Triannual progress report, October 1979-January 1980

Progress is summarized concerning magnetic fusion energy materials, laser fusion energy, aluminium-air battery and vehicle, geothermal research, oil-shale research, nuclear waste management, office of basic energy sciences research, and materials research notes. (FS)

Date: March 31, 1980

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Crystal-field splitting in Pr dideuteride

From inelastic neutron scattering experiments, it is concluded that the crystal-field splitting in PrD/sub 1.95/ is 41 meV. Because of this high value, the antiferromagnetic ordering below T/sub N/ = 2.3 K is ascribed to a magnetic ground state, probably GAMMA/sub 5/, of the Pr/sup 3 +/ ions.

Date: August 1, 1985

Creator: Arons, R. R.; Cable, J. W. & Nicklow, R. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Correlation theory applied to the static and dynamic properties of EuO and EuS

The paramagnetic scattering was recently measured for EuO. It was found that spin-wave-like excitations develop for wave vectors approaching the zone boundary. The spectrum was found to be well described by damped harmonic oscillators (also called the two-pole-approximation). This approximation was used previously in the correlation theory primarily to calculate static properties. Selfconsistent dynamic and static calculations have been performed for EuO, which is an ideal Heisenberg magnet wit… more

Date: October 1, 1981

Creator: Lindgard, P.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Muon spin relaxation in CeCu/sub 2/Si/sub 2/ and muon Knight shift in various heavy-fermion systems

Positive muon spin precession has been observed in varius heavy-fermion systems in the transverse external magnetic field. In the superconductor CeCu/sub 2.1/Si/sub 2/, the relaxation rate of muon spins increases rapidly with decreasing temperature below T/sub c/. This is interpreted as the results of the inhomogeneous fields due to the imperfect penetration of the external field into the type-II superconducting state. The magnetic-field penetration depth lambda is derived from the observed muo… more

Date: January 1, 1986

Creator: Uemura, Y. J.; Kossler, W. J.; Hitti, B.; Kempton, J. R.; Schone, H. E.; Yu, X. H. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Tricritical behavior in the ferromagnetic superconductor ErRh/sub 4/B/sub 4/

A new tricritical point on the phase boundary between the superconducting vortex phase and the normal paramagnetic phase of ErRh/sub 4/B/sub 4/ is presented. The microscopic origin of the tricritical point and the expected tricritical behavior are briefly discussed.

Date: August 1, 1985

Creator: Crabtree, G.W.; Kalia, R.K.; Hinks, D.G.; Behroozi, F. & Tachiki, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department