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Filled skutterudite antimonides: Validation of the electron-crystal phonon-glass approach to new thermoelectric materials

Description: After a brief review of the transport and thermoelectric properties of filled skutterudite antimonides, the authors present resonant ultrasound, specific heat, and inelastic neutron scattering results that establish the existence of two low-energy vibrational modes in the filled skutterudite LaFe{sub 3}CoSb{sub 12}. It is likely that at least one of these modes represents the localized, incoherent vibrations of the La ion in an oversized atomic {open_quotes}cage{close_quotes}. These results support the usefulness of weakly bound, {open_quotes}rattling{close_quotes} ions for the improvement of thermoelectric performance.
Date: April 1, 1997
Creator: Mandrus, D.; Sales, B.C. & Keppens, V.
Partner: UNT Libraries Government Documents Department

Chemical and sonochemical approaches to the formation of VO{sub 2} films and VO{sub 2}-impregnated materials

Description: 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 dioxide. The advantage of this approach to the formation of VO{sub 2} is that the V{sub 2}O{sub 5} sol can be used to impregnate porous materials, which are then heated treated to form an optically active composite material. The switching properties of the VO{sub 2} films are investigated using optical and resistivity measurements, and the results are compared to those obtained for VO{sub 2}-films prepared by more-conventional methods.
Date: November 1, 1997
Creator: Keppens, V.; Mandrus, D. & Boatner, L.A.
Partner: UNT Libraries Government Documents Department

Filled skutterudite antimonides: Validation of the electron-crystal phonon-glass approach to new thermoelectric materials

Description: After a brief review of the transport and thermoelectric properties of filled skutterudite antimonides, we present resonant ultrasound, specific heat, and inelastic neutron scattering results that establish the existence of two low-energy vibrational modes in the filled skutterudite LaFe{sub 3}CoSb{sub 12}. It is likely that at least one of these modes represents the localized, incoherent vibrations of the La ion in an oversized atomic {open_quotes}cage.{close_quotes} These results support the usefulness of weakly bound, {open_quotes}rattling{close_quotes} ions for the improvement of thermoelectric performance.
Date: April 1, 1997
Creator: Mandrus, D.; Dai, P. & Keppens, V.
Partner: UNT Libraries Government Documents Department

The formation of metal/metal-matrix nano-composites by the ultrasonic dispersion of immiscible liquid metals

Description: Ultrasonic energy has been used to disperse one liquid metallic component in a second immiscible liquid metal, thereby producing a metallic emulsion. Upon lowering the temperature of this emulsion below the mp of the lowest-melting constituent, a metal/metal-matrix composite is formed. This composite consists of sub-micron-to-micron- sized particles of the minor metallic phase that are embedded in a matrix consisting of the major metallic phase. Zinc-bismuth was used as a model system, and ultrasonic dispersion of a minor Bi liquid phase was used to synthesize metal/metal-matrix composites. These materials were characterized using SEM and energy-dispersive x-ray analysis.
Date: December 1, 1996
Creator: Keppens, V.M.; Mandrus, D.; Boatner, L.A. & Rankin, J.
Partner: UNT Libraries Government Documents Department