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in creator/contributor: "Boatner, L"

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Physical and Chemical Characteristics of Lead-Iron Phosphate Nuclear Waste Glasses

Experimental determinations of the properties of lead-iron phosphate glasses pertinent to their application to the problem of permanently disposing of high-level nuclear wastes have been carried out. These investigations included studies of the composition and physical properties of nuclear waste glasses (NWG), as well as the effect of preparation conditions. Lead-iron phosphate nuclear waste glasses were prepared by dissolving simulated US defense wastes or simulated commercial power reactor w… more

Date: May 1, 1985

Creator: Sales, B. C. & Boatner, L. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Electrical-Conductivity Measurements of Leachates for the Rapid Assessment of Wasteform Corrosion Resistance

Measurements of the electrical conductivity of leachate solutions as a function of time can be used as an efficient, informative means of evaluation and comparison in the development of nuclear waste forms and in the preliminary analysis of their corrosion resistance in distilled water. Three separate applications of this technique are described in this work. These are: (1) its use in the optimization of the corrosion resistance of a crystalline wasteform (monazite); (2) a study of the protecti… more

Date: January 1, 1982

Creator: Sales, B. C.; Petek, M. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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EPR investigations of impurities in the lanthanide orthophosphates

Lanthanide orthophosphates formed from elements in the first half of the 4f transition series are analogs of the monoclinic mineral monazite. The known geologic properties of this mineral make the general class of lanthanide orthophosphate compounds attractive substances for long-term containment and disposal of ..cap alpha..-active actinide nuclear wastes. EPR spectroscopy has been used to investigate the structural properties and solid state chemical properties of impurities in these material… more

Date: September 1, 1980

Creator: Abraham, M. M.; Boatner, L. A. & Rappaz, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Characterization of nuclear waste forms by EPR spectroscopy

Single crystals of LaPO/sub 4/ have been grown with the addition of various amounts of PW-4b simulated waste, and the EPR spectra of Gd/sup 3 +/ in these samples have been compared with that obtained for a pure LaPO/sub 4/ single crystal. The relationship between the average linewidth of two symmetric EPR transitions and their magnetic field separation for pure and PW-4b doped LaPO/sub 4/ crystals are shown quantitatively. These measurements were carried out for four different crystals and two … more

Date: October 1, 1980

Creator: Boatner, L. A.; Abraham, M. M. & Rappaz, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Lanthanide orthophosphates as a matrix for solidified radioactive defense and reactor wastes

Lanthanum phosphate is a promising host material for reprocessed light water reactor wastes (e.g., PW-4b). This is demonstrated by the high density of the composite waste form and by the low leach rates of both Cs and Sr. Additionally, crystallographic data on LaPO/sub 4/ pellets loaded with 10 wt % simulated PW-4b indicate the presence of only one phase, i.e., monoclinic monazite. The rare-earth orthophosphates have also been shown to be a viable waste form for Savannah River (SRW) defense was… more

Date: January 1, 1981

Creator: Petek, M.; Abraham, M. M. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Low Temperature Thermal Conductivity of Ktao/Sub 3/ and Ktn Single Crystals

Thermal conductivity of three KTaO/sub 3/ mixed crystals containing different impurities was measured. Specific heat data show large discrepancies with the calculated Debye contribution so the question of the existence of a phase transition below 10/sup 0/K remains open. (FS)

Date: January 1, 1979

Creator: de Gooer, A. M.; Salce, B. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Growth of Large Detector Crystals. Crada Final Report

In the course of a collaborative research effort between L.A. Boatner of Oak Ridge National Laboratory and Prof. Alex Lempicki of the Department of Chemistry of Boston University, a new highly efficient and very fast scintillator for the detection of gamma-rays was discovered. This new scintillator consists of a single crystal of lutetium orthophosphate (LuPO{sub 4}) to which a small percentage of trivalent cerium is added as an activator ion. The new lutetium orthophosphate-cerium scintillator… more

Date: June 18, 1997

Creator: Boatner, L. A. & Samuelson, S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Microwave Processing for Advance Electro-Optic Materials

This project addressed the technical and scientific goals of developing new methods for the formation of striation-free single crystals of potassium tantalate niobate. This solid-solution system has the potential for serving as a general electro-optic material with a wide range of optical applications. The performance of the material is, however, severely limited by the effects of compositional inhomogeneity that is generally induced during the single crystal growth process due to the nature of… more

Date: June 1, 2000

Creator: Boatner, L. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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New Crystal-Growth Methods for Producing Lattice-Matched Substrates for High-Temperature Superconductors

This effort addressed the technical problem of identifying and growing, on a commercial scale, suitable single-crystal substrates for the subsequent deposition of epitaxial thin films of high temperature semiconductors such as GaN/AlN. The lack of suitable lattice-matched substrate materials was one of the major problem areas in the development of semiconducting devices for use at elevated temperatures as well as practical opto-electronic devices based on Al- and GaN technology. Such lattice-ma… more

Date: June 24, 2008

Creator: Boatner, L. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Ferroelectric-to-Relaxor Crossover and Oxygen Vacancy Hopping in Compositionally-Disordered Perovskites - Kta(1-X)Nb(X)O(3):Ca

It is shown that lattice disorder induced by Nb and Ca substitution has a strong influence on the dielectric and relaxational properties of KTaO{sub 3}. Both substituents are believed to occupy off-center positions at the Ta site, and the difference in valence between the Ca{sup 2+} and Ta{sup 5+} ions leads to the formation of oxygen vacancies (V{sub 0}). Specifically, for a KTa{sub 1{minus}x}Nb{sub x}O{sub 3}:Ca crystal with x = 0.023 and with a 0.055 at.% Ca doping they observe: (1) a ferroe… more

Date: July 26, 1999

Creator: Samara, G. A. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Time Resolved Reflectivity Measurements in Pb-Implanted Srtio/Sub 3/

Time resolved optical reflectivity (TRR) is a simple and elegant technique for dynamically monitoring the interface motion that occurs during crystallization of thin films and amorphous layers on crystalline substrates. This in situ technique has enabled measurements of the solid-phase epitaxial regrowth rate of amorphous silicon layers produced by ion implantation to be extended by over five orders of magnitude to rates in excess of 10/sup 6/ /angstrom//s. TRR is also well suited to measuremen… more

Date: June 1, 1989

Creator: McCallum, J. C.; Rankin, J.; White, C. W. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Rutherford Backscattering Investigation of the Corrosion of Borosilicate Glass

The RBS spectra from Frit 21 borosilicate glasses doped with 5 wt % UO/sub 2/, SrO, or Cs/sub 2/O show that: during the initial stages of leaching (0 to 3 h) there is a substantial (300 to 500%) enhancement in the concentration of U, Sr, Ca, and Ti in the outer surface layer and that this enhancement is accompanied by a large depletion of Na, Si, and Cs; and upon further leaching under static conditions (24 h) the leached surface layer composition is indistinguishable from the unleached surface… more

Date: October 1, 1981

Creator: Sales, B. C.; Boatner, L. A.; Naramoto, H. & White, C. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Chemical and ceramic methods for the safe storage of actinides using monazite. 1997 annual progress report

'Oak Ridge National Laboratory (ORNL) and the Rockwell Science Center of Thousand Oaks, California, are carrying out a joint investigation of the chemical, physical, thermal, and radiation-resistance properties of the lanthanide orthophosphates (monazites) in both ceramic and single-crystal form with the objective of developing the scientific and technical base required for the application of these materials to the storage or disposal of actinide elements, including plutonium. An additional maj… more

Date: September 1997

Creator: Boatner, L. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Gravitational effects on the development of weld-pool and solidification microstructures

This research effort has as its objective the development of a quantitative understanding of the effects of both low- and high-g environments on the solidification microstructures and morphologies that are produced in alloy single crystals during a variety of melting and solidification processes. The overall goal of the effort is to delineate the nature of the roles played by natural convection, surface-tension-driven convection, and mass transport effects due to interactions associated with va… more

Date: September 1, 1994

Creator: Boatner, L. A.; David, S. A. & Workman, G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Luminescence Properties of ScPO{sub 4} Single Crystals

Flux-grown ScPO{sub 4} single crystals exhibit a number of luminescence bands in their x-ray-excited luminescence spectra - including sharp lines arising from rare-earth elements plus a number of broad bands at 5.6 cV, 4.4 eV, and 3 eV. The band at 5.6 eV was attributed to a self-trapped exciton (STE) [l], and it could be excited at 7 eV and higher energies. This luminescence is strongly polarized (P = 70 %) along the optical axes of the crystal and exhibits a kinetic decay time constant that v… more

Date: August 16, 1999

Creator: Boatner, L. A. & Trukhin, A. N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Growth of Large Single Crystals of Mgo

The progressive identification of new high-technology applications and requirements for MgO single crystals in the commercial realm, as well as in DOE and other government-agency project areas, has resulted in an increased demand and international market for this material. Specifically, the demand for MgO crystals in large sizes and quantities is presently increasing due to existing and developing applications that include: (a) MgO substrates for the formation of electro-optic thin films and de… more

Date: June 12, 1997

Creator: Boatner, L. A. & Urbanik, M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Chemical and Sonochemical Approaches to the Formation of Vo{Sub 2} Films and Vo{Sub 2}-Impregnated Materials

A new chemical and chemical/ultrasonic approach to the preparation of VO{sub 2} films and VO{sub 2}-impregnated bulk materials has been developed. In this approach, a V{sub 2}O{sub 5} sol prepared by quenching is used to coat SiO{sub 2} substrates. The resulting gel-film is heat treated in a reducing atmosphere to form a film identified as VO{sub 2} from the results of X-ray diffraction and both optical and resistivity measurements, which reveal the phase transition characteristic of vanadium d… more

Date: November 1, 1997

Creator: Keppens, V.; Mandrus, D. & Boatner, L. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Promethium (Pm/sup 3 +/) solid state laser

The achievement of stimulated emission from the trivalent promethium ion is reported. (DLC)

Date: January 1, 1987

Creator: Shinn, M. D.; Krupke, W. F.; Kirchoff, T. A.; Finch, C. B. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The formation of Al{sub 2}O{sub 3}/V{sub 2}O{sub 3} multilayer structures by high-dose ion implantation

High-resolution TEM, RBS-channeling and x-ray-diffraction techniques have been used to characterize multilayered structures formed by the high-dose co-implantation of vanadium and oxygen into single crystals of {alpha}-Al{sub 2}O{sub 3}. Thin, two-dimensional multilayered structures have been formed by implanting c-axis and a-axis-oriented single crystals of Al{sub 2}O{sub 3} at room temperature with vanadium (10{sup 17} ions/cm{sup 2} at 300 keV) and oxygen (2 x 10{sup 17} ions/cm{sup 2}, 120 … more

Date: April 1, 1995

Creator: Gea, L. A.; Boatner, L. A.; Budai, J. D. & Rankin, J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Chemical and Ceramic Methods Toward Safe Storage of Actinides Using Monazite. 1998 Annual Progress Report

'The use of ceramic monazite, (La,Ce)PO{sub 4}, for sequestering actinides, especially plutonium, and some other radioactive waste elements (rare earths e.g.) and thus isolating them from the environment has been championed by Lynn Boatner of ORNL. It may be used alone or, as it is compatible with many other minerals in nature, can be used in composite combinations. Natural monazite, which almost invariably contains Th and U, is often formed in hydrothermal pegmatites and is extremely water res… more

Date: June 1, 1998

Creator: Morgan, P. E. D. & Boatner, L. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Optically Active Surfaces Formed by Ion Implantation and Thermal Treatment

Embedded VO{sub 2} precipitates have been formed in single-crystal sapphire by the ion co-implantation of vanadium and oxygen and subsequent thermal annealing. The embedded VO{sub 2} particles have been shown to exhibit an optical switching behavior that is comparable to that of continuous thin films. In this work, the mechanisms of formation of these optically active particles are investigated. It is shown that precipitation of the vanadium dioxide phase is favored when the thermal treatment i… more

Date: August 1, 1996

Creator: Gea, L. A.; Boatner, L. A.; Evans, H. M. & Zuhr, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Response of Zircon to Electron and Ne{Sup +} Irradiation

Zircon (ZrSiO{sub 4}) is an actinide host phase in vitreous ceramic nuclear waste forms and a potential host phase for the disposition of excess weapons plutonium. In the present work, the effects of 800 and 900 keV electron and 1 MeV Ne{sup +} irradiations on the structure of single crystals of ZrSiO{sub 4} have been investigated. The microstructural evolution during the irradiations was studied in situ using a high-voltage electron microscope interfaced to an ion accelerator at Argonne Nation… more

Date: December 31, 1997

Creator: Devanathan, R.; Weber, W. J. & Boatner, L. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Raman spectra of MOCVD-grown ferroelectric PbTiO{sub 3} thin films

Lead titanate (PbTiO{sub 3}) has been grown on a variety of substrates by using the metalorganic chemical vapor deposition (MOCVD) technique. The substrates employed included Si, GaAs, MgO, fused-quartz, sapphire, and KTaO{sub 3}. Raman spectra from these heterostructures are presented. All of the films exhibited the strong, narrow spectral features characteristic of PbTiO{sub 3} perovskite-oxide crystals and indicative of high crystalline quality. The temperature behavior of the Raman modes, i… more

Date: December 31, 1993

Creator: Feng, Z. C.; Kwak, B. S.; Erbil, A. & Boatner, L. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Temperature-induced phase transitions during ion-beam irradiation of the perovskite-structure oxides

Several perovskite-structure oxide compounds, including CaTiO{sub 3}, SrTiO{sub 3}, BaTiO{sub 3}, KNbO{sub 3}, and KTaO{sub 3} were irradiated by 800 keV Kr{sup +} ions in order to investigate and compare their response to heavy-ion irradiation. The critical amorphization temperature T{sub c}, above which amorphization temperature T{sub c}, above which amorphization could not be induced, was found to increase in the order SrTiO{sub 3} {yields} CaTiO{sub 3} {yields} BaTiO{sub 3} {yields} KNbO{su… more

Date: December 1997

Creator: Meldrum, A.; Boatner, L. A. & Ewing, R. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department