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in creator/contributor: "Voigt, J."

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Aqueous precipitation: Population balance modeling and control in multi-cation systems

Efficient separation of metal species from aqueous streams by precipitation techniques requires a fundamental understanding of the processes that occur during precipitation. These processes include particle nucleation, particle growth by solute deposition, agglomerate formation, and agglomerate breakup. Population balance method has been used to develop a kinetic model that accounts for these competing kinetic processes. The usefulness of the model is illustrated through its application to prec… more

Date: March 1996

Creator: Voigt, J. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Structure-property relationships of antiferroelectric Pb(Zr, Ti)O{sub 3} based materials: Hydrostatic depoling characteristics

A novel technique has been developed for the synthesis of homogeneous, weakly agglomerated highly filterable Pb(Zr, Ti)O{sub 3} (PZT) powders. PZT 95/5 based ceramics were fabricated from these powders to determine interrelationships among microstructure, dielectric properties and pressure induced ferroelectric (FE) to antiferroelectric (AFE) phase transitions. Initial measurements indicate that microstructure has a substantial effect on hydrostatic depoling characteristics. While smaller grain… more

Date: September 1, 1997

Creator: Tuttle, B.; Voigt, J. & Moore, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Solution synthesis and characterization of lithium manganese oxide cathode materials

A nonaqueous coprecipitation process has been developed to prepare controlled stoichiometry lithium manganese oxalate precipitates. The process involved mixing a methanolic Li-Mn nitrate solution with a methanolic solution containing tetramethylammonium oxalate as the precipitating agent. The resulting oxalates were readily converted to a variety of phase pure lithium manganese oxides at moderate temperatures ({le}600{degrees}C), where the phase formed was determined by the initial Li/Mn ratio … more

Date: July 1, 1995

Creator: Voigt, J.A.; Boyle, T.J. & Doughty, D.H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Densification and crystallization of zirconia thin films prepared by sol-gel processing

We have investigated the effects of precursor nature and heat treatment schedule on the densification and crystallization behavior of sol-gel derived zirconia thin films. Precursor solutions were prepared from n-propanol, zirconium (IV) n-propoxide, and either acetic acid, or 2,4-pentanedione (acac) and water additions. By controlling the ligand type and ligand-to-metal ratio, we were able to prepare films which displayed significant differences in densification behavior. We attribute the dissi… more

Date: December 31, 1993

Creator: Schwartz, R. W.; Voigt, J. A.; Buchheit, C. D. & Boyle, T. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electrochemical impedance spectroscopy studies of lithium diffusion in doped manganese oxide

Cathode performance is critical to lithium ion rechargeable battery performance; effects of doping lithium manganese oxide cathode materials on cathode performance are being investigated. In this paper, Li diffusion in Al-doped LiMn{sub 2}O{sub 4} was studied and found to be controlled by the quantity of Al dopant. Electrochemical cycling was conducted at 0.5mA/cm{sub 2}; electrochemical impedance spectra were taken at open circuit potential, with impedance being measured at 65 kHz-0.01 Hz. As … more

Date: June 1, 1996

Creator: Johnson, B. J.; Doughty, D. H.; Voigt, J. A. & Boyle, T. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Lithium ion rechargeable systems studies

Lithium ion systems, although relatively new, have attracted much interest worldwide. Their high energy density, long cycle life and relative safety, compared with metallic lithium rechargeable systems, make them prime candidates for powering portable electronic equipment. Although lithium ion cells are presently used in a few consumer devices, e.g., portable phones, camcorders, and laptop computers, there is room for considerable improvement in their performance. Specific areas that need to be… more

Date: February 1, 1995

Creator: Levy, S.C.; Lasasse, R.R.; Cygan, R.T. & Voigt, J.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Neutron diffraction studies on recrystallization of solution derived lead zirconate titanates

We performed neutron powder diffraction on solution-derived lead zirconate titanates (PZT). Three compositions, PZT 45/55, PZT 20/80 and PbTiO{sub 3}, were investigated. The materials were annealed so that the perovskite phase had just begun to grow from the precursor phase. In our materials this precursor phase is the pyrochlore rather than fluorite phase. The results show that in the pyrochlore phase, the (Ti,Zr) and the Pb are ordered in their crystallographic sites while the O are essential… more

Date: December 31, 1994

Creator: Morosin, B.; Tuttle, B. A.; Voigt, J. A.; Lawson, A. C. & Kwei, G. H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Control of thin film processing behavior through precursor structural modifications

In the sol-gel processing of ceramic thin films it has been frequently noted that the processing behavior, microstructure and properties of the films are dependent on the nature of the coating solution. In an attempt to understand such thin film processing-property relationships, the authors have systematically investigated the effects of varying the precursor nature on thin film densification and crystallization for ZrO{sub 2} and TiO{sub 2} films. Metal alkoxide starting compounds, e.g., zirc… more

Date: February 1, 1995

Creator: Schwartz, R. W.; Voigt, J. A.; Boyle, T. J.; Christenson, T. A. & Buchheit, C. D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Chemically Prepared Lead Magnesium Niobate Dielectrics

A chemical solution powder synthesis technique has been developed that produces fine uniform powders of lead magnesium niobate (PMN) with 60 to 80 nm crystallite size. The synthesis technique was based on the dissolution of lead acetate and alkoxide precursors in acetic acid followed by precipitation with oxalic acid/propanol solutions. Lead magnesium niobate ceramics fabricated from these chemically derived powders had smaller, more uniform grain size and higher dielectric constants than ceram… more

Date: January 1, 1998

Creator: Tuttle, B. A.; Voigt, J. A.; Sipola, D. L.; Olson, W. R. & Goy, D. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Chemically prepared lead magnesium niobate dielectrics

A chemical solution powder synthesis technique has been developed that produces first, uniform powders of lead magnesium niobate (PMN) with 60 to 80 nm crystallite size. The synthesis technique was based on the dissolution of lead acetate and alkoxide precursors in acetic acid followed by precipitation with oxalic acid/propanol solutions. Lead magnesium niobate ceramics fabricated from these chemically derived powders had smaller, more uniform grain size and higher dielectric constants than cer… more

Date: November 1, 1998

Creator: Tuttle, B. A.; Voigt, J. A.; Sipola, D. L.; Olson, W. R. & Goy, D. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Ceramic powder synthesis in supercritical fluids

Gas-phase processing plays an important role in the commercial production of a number of ceramic powders. These include titanium dioxide, carbon black, zinc oxide, and silicon dioxide. The total annual output of these materials is on the order of 2 million tons. The physical processes involved in gas-phase synthesis are typical of those involved in solution -phase synthesis: chemical reaction kinetics, mass transfer, nucleation, coagulation, and condensation. This report focuses on the work don… more

Date: April 1, 1996

Creator: Adkins, C. L. J.; Russick, E. M.; Cesarano, J.; Tadros, M. E. & Voigt, J. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Relationships between ferroelectric 90{degree} domain formation and electrical properties of chemically prepared Pb(Zr,Ti)O{sub 3} thin films

For PZT films deposited on Pt coated substrates, remanent polarization is a monotonic function of thermal expansion of the substrate, a result of 90{degree} domain formation occurring as the film is cooled through the transformation temperature. PZT film stress in the vicinity of the Curie point controls 90{degree} domain assemblages within the film. PZT films under tension at the transformation temperature area-domain oriented; whereas, films under compression at the transformation temperature… more

Date: July 1, 1994

Creator: Tuttle, B. A.; Garino, T. J. Voigt, J. A.; Headley, T. J.; Dimos, D. & Eatough, M. O.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Oriented lead zirconate titanate thin films: Characterization of film crystallization

Film processing temperature and time was varied to characterize the pyrochlore-to-perovskite crystallization of solution-derived PZT 20/80 thin films. 3000 {Angstrom} thick films were prepared by spin deposition using <100> single crystal MgO as substrate. By controlled rapid thermal processing, films at different stages in the perovskite crystallization process were prepared with the tetragonal PZT 20/80 phase being <100>/<001> oriented relative to the MgO surface. An activation energy for the… more

Date: November 1, 1993

Creator: Voigt, J. A.; Tuttle, B. A.; Headley, T. J.; Eatough, M. O.; Lamppa, D. L. & Goodnow, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Solution Synthesis and Processing of PZT Materials for Neutron Generator Applications

A new solution synthesis route has been developed for the preparation of lead-based ferroelectric materials (patent filed). The process produces controlled stoichiometry precursor powders by non-aqueous precipitation. For a given ferroelectric material to be prepared, a metal acetate/alkoxide solution containing constituent metal species in the appropriate ratio is mixed with an oxalic acid/n-propanol precipitant solution. An oxalate coprecipitate is instantly fonned upon mixing that quantitati… more

Date: December 1, 1998

Creator: Anderson, M. A.; Ewsuk, K. G.; Montoya, T. V.; Moore, R. H.; Sipola, D. L.; Tuttle, B. A. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

La{sub 0.5}Sr{sub 0.5}CoO{sub 3} electrode technology for Pb(Zr, Ti)O{sub 3} thin film nonvolatile memories

Oxide electrode technology is investigated for optimization of Pb(Zr,Ti)O{sub 3} (PZT) thin film capacitor properties for high density nonvolatile memory applications. PZT thin film capacitors with RF sputter deposited La{sub 0.5}Sr{sub 0.5}CoO{sub 3} (LSCO) electrodes have been characterized with respect to the following parameters: initial dielectric hysteresis loop characteristics, fatigue performance, microstructure and imprint behavior. Our studies have determined that the fatigue of PZT c… more

Date: July 1, 1995

Creator: Tuttle, B. A.; Al-Shareef, H. N.; Warren, W. L.; Raymond, M. V.; Headley, T. J. & Voigt, J. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Synthesis of nanocrystalline barium-hexaferrite from nanocrystalline goethite using the hydrothermal method: Particle size evolution and magnetic properties

To characterize particle size/magnetic property relationships, 9 to 50 nm in diameter barium hexaferrite, BaFe{sub 12}O{sub 19} (BHF), particles were prepared using a new synthesis route. By replacing the conventional 50 to 100 nm particles of goethite with nanocrystalline goethite produced via the microwave anneal method of Knight and Sylva, nanocrystalline BHF was synthesized using the hydrothermal method. Evolution of particle size and morphology with respect to concentration and heat treatm… more

Date: March 1, 1997

Creator: Penn, R. L.; Banfield, J. F. & Voigt, J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Modeling, synthesis and characterization of LiMn{sub 2}O{sub 4} spinels

The authors report on an integrated program to understand the fundamentals of LiMn{sub 2}O{sub 4} performance as a cathode for lithium ion rechargeable batteries. Specifically, this program is designed to address the effects of doping on the crystal chemistry, lattice constants, and electrochemical performance. The work is being expanded to include studies on LiCoO{sub 2} and LiNiO{sub 2}.

Date: November 1, 1997

Creator: Doughty, D. H.; Ingersoll, D.; Cygan, R. T.; Westrich, H. R.; Rodriguez, M. A.; Boyle, T. J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ferroelectric thin film microstructure development and related property enhancement

Factors that control phase evolution, microstructural development and ferroelectric domain assemblage are evaluated for chemically prepared lead zirconate titanate (PZT) thin films. Zirconium to titanium stoichiometry is shown to strongly influence microstructure. As Ti content increases, there is an apparent enhancement of the perovskite phase nucleation rate, grain size becomes smaller, and the amount of pyrochlore phase, if present, decreases. While the pyrochlore matrix microstructure for n… more

Date: November 1, 1993

Creator: Tuttle, B.; Voigt, J. A.; Headley, T. J.; Potter, B. G.; Dimos, D.; Schwartz, R. W. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department