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Insulator to correlated metal transition in V_1-xMo_xO_2

Description: The change from metallic to insulating states is one of the most dramatic transitions that solids undergo on cooling or chemical doping. Many materials display this transition, but only a handful have the right combination of crystal structure and physical properties to serve as model systems. VO{sub 2} is one of those materials. Using Mo as a chemical dopant in VO{sub 2}, we find unanticipated phenomenology for both the electronic and structural characteristics of the resulting insulator to me… more
Date: January 1, 2009
Creator: Klimczuk, Tomasz; Ronning, Filip; Holman, Katherine; Mcqueen, Tyrel M; Williams, Anthony J; Stephens, P W et al.
Partner: UNT Libraries Government Documents Department
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Optical Spectroscopy of the Structural Phase Transition of VO{sub 2} Nanocrystals in Optical Fibers and Thin Films

Description: The optical spectroscopy of VO{sub 2} nanocrystals in planar and fiber-waveguide geometries shows a size- and doping-dependent structural semiconductor-to-metal phase transition and a shape-dependent surface plasmon resonance, with unusual linear and nonlinear applications possibilities.
Date: December 4, 2001
Creator: Lopez, R.
Partner: UNT Libraries Government Documents Department
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Oxidation performance of V-Cr-Ti alloys

Description: Vanadium-base alloys are being considered as candidates for the first wall in advanced V-Li blanket concepts in fusion reactor systems. However, a primary deterrent to the use of these alloys at elevated temperatures is their relatively high affinity for interstitial impurities, i.e., O, N, H, and C. The authors conducted a systematic study to determine the effects of time, temperature, and oxygen partial pressure (pO{sub 2}) in the exposure environment on O uptake, scaling kinetics, and scale … more
Date: April 3, 2000
Creator: Natesan, K. & Uz, M.
Partner: UNT Libraries Government Documents Department
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Phase transitions in insertion electrodes for lithium batteries

Description: Phase transitions that occur during lithium insertion into layered and framework structures are discussed in the context of their application as positive and negative electrodes in lithium-ion batteries. The discussion is focused on the two-dimensional structures of graphite, LiNi{sub 1{minus}x}M{sub x}O{sub 2} (M = Co, Ti and Mg), and Li{sub 1.2}V{sub 3}O{sub 8}; examples of framework structures with a three-dimensional interstitial space for Li{sup +}-ion transport include the spinel oxides a… more
Date: February 2, 2000
Creator: Thackeray, M. M.
Partner: UNT Libraries Government Documents Department
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Tungsten-vanadium oxide sputtered films for Electrochromic Devices

Description: Mixed vanadium and tungsten oxide films with compositions ranging from 0 to 100% vanadium (metals basis) were prepared by reactive sputtering from metallic vanadium and tungsten targets in an atmosphere of argon and oxygen. The vanadium content varied smoothly with the fraction of total power applied to the vanadium target. Films containing vanadium were more color neutral than pure tungsten oxide films, tending to gray-brown at high V fraction. The electrochromic switching performance of these… more
Date: October 1, 1998
Creator: Michalak, F.; Richardson, T.; Rubin, M.; Slack, J. & von Rottkay, K.
Partner: UNT Libraries Government Documents Department
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First-principles calculation of atomic structure and electrochemical potential of Li{sub 1+x}V{sub 3}O{sub 8}.

Description: Interest in the {gamma}-bronze, Li{sub 1+x}V{sub 3}O{sub g}, as a possible electrode material in rechargeable Li batteries has stimulated several experimental studies on this system. Detailed interpretation of the electrochemical and physical-property measurements is complicated by uncertainties regarding the structural arrangement of Li atoms as a function of x and by a phase transition between two monoclinic structures ({gamma}{sub a}, {gamma}{sub b}) during intercalation. To elucidate the at… more
Date: August 27, 1998
Creator: Benedek, R.
Partner: UNT Libraries Government Documents Department
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Electrically Insulating Films Deposited on V-4Cr-4Ti by Reactive CVD

Description: In the design of liquid-metal blankets for magnetic fusion reactors, corrosion resistance of structural materials and the magnetohydrodynamic forces and their influence on thermal hydraulics and corrosion are major concerns. Electrically insulating CaO films deposited on V-4%Cr-4%Ti exhibit high-ohmic insulator behavior even though a small amount of vanadium from the alloy become incorporated into the film. However, when vanadium concentration in the film is > 15 wt.%, the film becomes conducti… more
Date: April 1, 1998
Creator: Park, J. H.
Partner: UNT Libraries Government Documents Department
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Structure and electrochemical potential simulation for the cathode material Li(1+x)V(3)O(8).

Description: The structure and electrochemical potential of monoclinic Li{sub 1+x}V{sub 3}O{sub 8} were calculated within the local-density-functional-theory framework by use of plane-wave-pseudopotential methods. Special attention was given to the compositions 1+x=1.2 and 1+x=4, for which x-ray diffraction structure refinements are available. The calculated low-energy configuration for 1+x=4 is consistent with the three Li sites identified in x-ray diffraction measurements and predicts the position of the … more
Date: December 5, 1997
Creator: Benedek, R.; Thackeray, M. M. & Yang, L. H.
Partner: UNT Libraries Government Documents Department
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Structural and electrochemical potential simulation for the cathode material Li{sub 1+x}V{sub 3}O{sub 8}

Description: The structure and electrochemical potential of monoclinic Li{sub 1+x}V{sub 3}O{sub 8} were calculated within the local-density-functional-theory framework by use of plane-wave-pseudopotential methods. Special attention was given to the compositions 1+x=1.2 and 1+x=4, for which x-ray diffraction structure refinements are available. The calculated low-energy configuration for 1+x=4 is consistent with the three Li sites identified in x-ray diffraction measurements and predicts the position of the … more
Date: December 1, 1997
Creator: R. Benedek, R.; Thackeray, M.M. & Yang, I.H.
Partner: UNT Libraries Government Documents Department
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Excitations and possible bound states in the S = {1/2} alternating chain compound (VO){sub 2}P{sub 2}O{sub 7}

Description: Magnetic excitations in an array of (VO){sub 2}P{sub 2}O{sub 7} single crystals have been measured using inelastic neutron scattering. Until now, (VO){sub 2}P{sub 2}O{sub 7} has been thought of as a two-leg antiferromagnetic Heisenberg spin ladder with chains running in the a-direction. The present results show unequivocally that (VO){sub 2}P{sub 2}O{sub 7} is best described as an alternating spin-chain directed along the crystallographic b-direction. In addition to the expected magnon with mag… more
Date: July 30, 1997
Creator: Tennant, D. A.; Nagler, S. E. & Sales, B. C.
Partner: UNT Libraries Government Documents Department
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Magnetic excitations in (VO)HPO{sub 4}{center_dot}{1/2}H{sub 2}O

Description: The magnetic excitations of an antiferromagnetic spin dimer system, (VO)HPO{sub 4}{center_dot}{1/2}H{sub 2}O, are examined using inelastic neutron scattering. A dispersionless mode is found, consistent with expectations for a dimer excitation. The intensity variation of the mode reveals a V{sup 4+} - V{sup 4+} dimer separation of 4.43{angstrom}, almost 50% larger than the originally expected length.
Date: July 11, 1997
Creator: Garrett, A. W.; Nagler, S. E. & Tennant, D. A.
Partner: UNT Libraries Government Documents Department
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Optical indices of lithiated electrochromic oxides

Description: Optical indices have been determined for thin films of several electrochromic oxide materials. One of the most important materials in electrochromic devices, WO{sub 3}, was thoroughly characterized for a range of electrochromic states by sequential injection of Li ions. Another promising material, Li{sub 0.5}Ni{sub 0.5}O, was also studied in detail. Less detailed results are presented for three other common lithium-intercalating electrochromic electrode materials: V{sub 2}O{sub 5}, LiCoO{sub 2}… more
Date: September 1, 1996
Creator: Rubin, M.; Rottkay, K. von; Wen, S.J.; Ozer, N. & Slack, J.
Partner: UNT Libraries Government Documents Department
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Optically Active Surfaces Formed by Ion Implantation and Thermal Treatment

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

Capacity fade in thin-film lithium-V{sub 2}O{sub 5} cells

Description: Capacity fade with cycling of thin-film rechargeable Li/Lipon/V{sub 2}O{sub 5} cells, formed as electrochromic mirrors with ITO current collectors, has been studied by optical and impedance spectroscopy and extended cycling experiments. An irreversible decrease in the reflectivity observed in cells cycled between 3.6 to 1.5 V was attributed to a roughening of the Li surface at the Li-Lipon interface. Although the consequent loss of contact area might be the source of increasing cell resistance … more
Date: January 1, 1996
Creator: Kwak, B.S.; Bates, J.B. & Hart, F.X.
Partner: UNT Libraries Government Documents Department
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In situ laser raman spectroscopy during sequential oxidizing and reducing conditions for a vanadium-phosphorous-oxide catalyst

Description: A VPO catalyst prepared in an organic medium has been studied by in situ laser Raman spectroscopy under reaction conditions for n-butane oxidation to maleic anhydride. Data were obtainable at low laser power and short collection times. Raman characterization during continuous flow (steady state) revealed that the (VO){sub 2}P{sub 2}O{sub 7} phase was present. Sequential oxidizing (10% O{sub 2} in N{sub 2}) and reducing (2% n-butane in N{sub 2}) conditions were explored at 350{degree} and 400{de… more
Date: December 31, 1995
Creator: Soejarto, A.D.; Schrader, G.L. & Coulston, G.W.
Partner: UNT Libraries Government Documents Department
open access

Optical switching of coherent VO{sub 2} precipitates embedded in sapphire

Description: In this work, we report the formation of a new type of active or {open_quotes}smart{close_quote} surface that is produced by ion implantation and thermal processing. By co-implanting vanadium and oxygen into a single- crystal sapphire substrate and annealing the system under appropriate conditions, it was possible to form buried precipitates of vanadium dioxide that were crystallographically oriented with respect to the host Al{sub 2}O{sub 3} lattice. The implanted VO{sub 2} precipitate system … more
Date: December 31, 1995
Creator: Gea, L. A.; Boatner, L. A.; Budai, J. D. & Zuhr, R. A.
Partner: UNT Libraries Government Documents Department
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Mechanical properties of, and phase transformation in, V-Cr-Ti-O solid solutions

Description: Incorporation of O in the surface of V-Ti-Cr alloys has been investigated in controlled environments at 550-750{degrees}C. and tests were performed to determine the physical properties of V-Cr-Ti-O solid solutions. The amount of O in the alloys has been determined by weight-change measurements. Microhardness was used to determine O depth profiles in the alloys. X-ray, diffraction indicated a phase transformation from body-centered-cubic (bcc) to tetragonal in the highly stressed lattice because… more
Date: November 1, 1995
Creator: Park, J. H.; Kuppermann, D. & Park, E. T.
Partner: UNT Libraries Government Documents Department
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Sol-gel deposited electrochromic coatings

Description: Electrochromic devices have increasing application in display devices, switchable mirrors and smart windows. A variety of vacuum deposition technologies have been used to make electrochromic devices. The sol- gel process offers an alternative approach to the synthesis of optical quality and low cost electrochromic device layers. This study summarizes the developments in sol-gel deposited electrochromic films. The sol-gel process involves the formation of oxide networks upon hydrolysis-condensat… more
Date: June 1, 1995
Creator: Ozer, N. & Lampert, C.M.
Partner: UNT Libraries Government Documents Department
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Magnetic correlations in doped transition metal oxides

Description: The authors review recent reactor- and spallation-source-based neutron scattering experiments on the magnetic fluctuations and order in a variety of doped transition metal oxides. In particular, data are shown for the NiO chain compound, Y{sub 2{minus}x}Ca{sub x}BaNiO{sub 5}, the two-dimensional cuprate superconductors La{sub 2{minus}x}Sr{sub x}CuO{sub 4} and YBa{sub 2}Cu{sub 3} O{sub 6+x}, and the classical three-dimensional ``Mott-Hubbard`` system V{sub 2{minus}y}O{sub 3}.
Date: February 15, 1995
Creator: Aeppli, G.; Bao, W. & Broholm, C.
Partner: UNT Libraries Government Documents Department
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Superconductivity, magnetism and metal-insulator transitions in some ternary and pseudoternary 3d-, 4d- and 5d-metal oxides

Description: Electron conduction effects have been found to be particularly important in the metallic compounds LiV{sub 2}O{sub 4} and possibly Sr{sub 2}Ir{sub 1-x}Ru{sub x}O{sub 4} (x > 0.7), but not in metallic Sr{sub 1-x}La{sub x}VO{sub 3} (x < 0.7), and they cause the compounds Sr{sub 2}IrO{sub 4} and ZnV{sub 2}O{sub 4} to be (Mott-Hubbard) insulators. The LiV{sub 2}O{sub 4} spinel compound is especially interesting, because the V ions exhibit rather clear local moment (S = 1/2) behavior even though the… more
Date: December 31, 1994
Creator: Johnston, D. C.; Borsa, F.; Kim, K. H.; Manajan, A. V.; Miller, L. L.; Torgeson, D. R. et al.
Partner: UNT Libraries Government Documents Department
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Thin-film rechargeable lithium batteries

Description: Rechargeable thin-films batteries with lithium metal anodes, an amorphous inorganic electrolyte, and cathodes of lithium intercalation compounds have been fabricated and characterized. The cathodes include TiS{sub 2}, the {omega} phase of V{sub 2}O{sub 5}, and the cubic spinel Li{sub x}Mn{sub 2}O{sub 4} with open circuit voltages at full charge of about 2.5 V, 3.7 V, and 4.2 V, respectively. The development of these robust cells, which can be cycled thousands of times, was possible because of t… more
Date: November 1, 1993
Creator: Bates, J. B.; Gruzalski, G. R.; Dudney, N. J.; Luck, C. F. & Yu, X.
Partner: UNT Libraries Government Documents Department
open access

Rechargeable thin-film lithium batteries

Description: Rechargeable thin-film batteries consisting of lithium metal anodes, an amorphous inorganic electrolyte, and cathodes of lithium intercalation compounds have been fabricated and characterized. These include Li-TiS{sub 2}, Li-V{sub 2}O{sub 5}, and Li-Li{sub x}Mn{sub 2}O{sub 4} cells with open circuit voltages at full charge of about 2.5 V, 3.7 V, and 4.2 V, respectively. The realization of these robust cells, which can be cycled thousands of times, was possible because of the stability of the am… more
Date: September 1, 1993
Creator: Bates, J. B.; Gruzalski, G. R.; Dudney, N. J.; Luck, C. F. & Yu, X.
Partner: UNT Libraries Government Documents Department
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Hot gas desulfurization with sorbents containing mixed metal oxides

Description: Advanced power generation systems such as the integrated gasification combined cycle power generators and the molten carbonate fuel cells have stringent fuel gas desulfurization requirements and process economics dictates that this desulfurization be performed near the temperature of the gasification off-gas. The most advanced hot gas desulfurization technology today is based on the zinc ferrite sorbent which has several shortcomings such as zinc loss by evaporation, and incomplete regeneration… more
Date: December 31, 1992
Creator: Akyurtlu, J. F. & Akyurtlu, A.
Partner: UNT Libraries Government Documents Department
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