bluuebunny/crossref_metadata_2025_split huggingface dataset:
Disorderly conduct in Bi2Ln2Ti3O12 Aurivillius phases (Ln = La, Pr, Nd, Sm).
Authors: Hyatt Neil C. , Hriljac Joseph A. 
Published: April 2011

ABSTRACTThe synthesis and structure of triple layered Bi2Ln2Ti3O12 Aurivillius phases, prepared from K2Ln2Ti3O10 Ruddlesden - Popper precursors has been investigated. In structural terms, these materials may be considered as being composed of a regular intergrowth of [Bi2O2]2+ fluorite and [Ln2Ti3O10]2- perovskite-type layers. A significant degree of cation disorder is present in the Bi2Ln2Ti3O12 system, involving the cross substitution of Ln / Bi cations onto the Bi / Ln sites in the fluorite and perovskite-type layers, respectively. Bi / Ln disorder destabilises the presence of the Ln cation in the perovskite-type layer as the size mismatch of the Bi / Ln cations increases. Cation disorder in the Bi2Ln2Ti3O12 system is therefore significantly suppressed as the size of the lanthanide cation is reduced.
Nucleation and Growth of Gallium Oxide Tubes, Nanopaintbrushes and Nanowires from Molten Gallium
Authors: Sharma Shashank , Sunkara Mahendra K. , Graham Uschi M. , Davis Burtron H. 
Published: April 2011

ABSTRACTWe have synthesized highly crystalline β-gallium oxide tubes, nanowires, and unique one-dimensional structures in the form of nanopaintbrushes using molten gallium and microwave plasma containing a mixture of monoatomic oxygen and hydrogen. Multiple nucleation and growth of gallium oxide nanostructures occurred directly out of molten gallium upon exposure to an appropriate composition of hydrogen and oxygen in the gas phase. Gallium oxide nanowires were 20 to 100 nm thick and tens to hundreds of microns long. In addition to these morphologies, we also report for the first time, non-template based synthesis of novel 2-D networks of crystalline gallium oxide nanowires and nanotubes. Demonstration of this technique with gallium oxide certainly presents a new route for synthesis of nanostructures of other important metal oxides such as indium oxide, tin oxide, and zinc oxide.
Microstructural Aspects of the Ionic Transport Properties of Strontium-Substituted Lanthanum Cobaltites
Authors: Sitte W. , Bucher E. , Preis W. , Papst I. , Grogger W. , Hofer F. 
Published: April 2011

ABSTRACTThe ionic conductivity and microstructure of selected compositions of the solid solution La1-xSrxCoO3-δ (LSC) were examined with respect to possible vacancy ordering phenomena. Homogeneous samples of LSC were prepared by the glycine nitrate process. The ionic conductivity was obtained as a function of the oxygen partial pressure (-3.5 ≤ log[p(O2)/atm] ≤ 0.5) using a recently developed galvanostatic polarization technique. At 825°C the p(O2)-dependence of the ionic conductivity of La1-xSrxCoO3-° (x = 0.4 and 0.6) shows a distinct maximum. Although this behavior has yet to be explained unambiguously it is indicative of decreasing mobility of ionic charge carriers, e. g. due to cooperative vacancy ordering. From the temperature dependence of the ionic conductivity of La1-xSrxCoO3-° (x = 0.6) activation energies at constant nonstoichiometry (0.20 ≤ ° ≤ 0.28) were obtained. As vacancy association and microstructure are presumed to play a significant role we combined the results of ionic conductivity measurements and electron microscopical investigations. HRTEM images revealed a superstructure within microdomains of about 100 nm in size.
Structural behavior of zirconia thin films with different level of yttrium content
Authors: Petrovsky V. , Anderson H. U. , Petrovsky T. , Bohannan E. 
Published: April 2011

ABSTRACTThe preparation of dense, high conductive electrolyte layers is important for the development of intermediate temperature solid oxide fuel cells and other devices based on oxygen-ion conductivity. Thus a number of techniques have been used to produce these structures. This study makes use of one of these methods to produce dense nanocrystalline 0.1 to 1 micron layers of zirconia.Polymeric precursors were used to prepare zirconia films with different level of yttrium substitution. The films were annealed at a series of temperatures in the range of 400 to 1000°C and were characterized via scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that initially (after 400°C annealing) the films had cubic structure and grain size of ∼5 nm regardless of Y content. The situation changed when the annealing temperature was increased. Y (16mol %) stabilized zirconia (YSZ) did remain cubic over the entire temperature region investigated (up to 1000°C), but for compositions with lower Y content changes in crystal structure occurred. The samples with 4 and 8mol% Y transformed to the tetragonal phase at about 700°C, and undoped zirconia became monoclinic at the same temperature.The results were compared with sintered zirconia and it was shown that the behavior of thin films is quite similar to that of the sintered material, if the annealing temperature was high enough (>700°C). The main differences between polymeric prepared films and sintered material are the existence of the cubic structure at low temperatures (< 600°C) and lower transition temperatures to the high temperature phase, which can be explained by small initial grain size in polymer-derived zirconia.
Mixed Ionic – Electronic Conduction and Oxygen Permeation in Ba-In Based Oxides Doped with Transition Metals
Authors: Aizumi Yusuke , Takamura Hitoshi , Kamegawa Atsunori , Okada Masuo 
Published: April 2011

ABSTRACTThe electrical conductivity and oxygen permeability of transition-metal-doped (Ba0.3Sr0.2La0.5)2(In1-xTMx)2O5+ö(TM = Fe, Co, Mn and Sn; 0 ≤ × ≤ 0.5) have been investigated. The X-ray diffraction analysis revealed that all the samples had a cubic perovskite-type structure due to La3+doping on the alkaline earth site. For Fe-doped specimens, the lattice parameter of 0.414 nm for (Ba0.3Sr0.2La0.5)2In2O5+δlinearly decreased with increasing the Fe content, suggesting the incorporation of Fe into the matrix phase. Fe-doping for the In site enhanced the p-type conduction under a wide P(O2) range, and the p-type conductivity increased with increasing the Fe content without decreasing the ionic conductivity. The oxygen permeability was measured under the P(O2) difference between helium and air in the temperature range of 800 ∼ 1000 °C. For the Fe-doped specimens, the oxygen flux density of j(O2) increased with increasing the Fe content, and a maximum value of 0.5 μmol·cm-2·s-1was attained at 1000 °C for the membrane thickness of 1.0 mm.
Electrochemical NOx Sensors for Automotive Diesel Exhaust
Authors: Martin Louis P. , Pham Ai-Q. , Glass Robert S. 
Published: April 2011

ABSTRACTNew emissions regulations will increase the need for compact, inexpensive sensors for monitoring and control of automotive exhaust gas pollutants. Species of interest include hydrocarbons, carbon monoxide, and oxides of nitrogen (NOx). The current work is directed towards the development of fast, high sensitivity electrochemical NOx sensors for automotive diesel applications. We have investigated potentiometric NO sensors with good sensitivity and fast response when operated in 10% O2. The sensors consist of yttria-stabilized zirconia substrates attached with NiCr2O4 sensing electrodes and Pt reference electrodes. A composite NiCr2O4:Rh sensing electrode is shown to give significantly faster response than NiCr2O4 alone. The exact role of the Rh in enhancing the response speed is not clear at present. However, the Rh appears to accumulate at the contacts between the NiCr2O4 particles and may enhance the inter-particle electronic conduction. Ongoing testing of these sensors is being performed to elucidate the sensing mechanisms and to quantify cross sensitivity to, for example, NO2.
Preparation of (La, Li)TiO3 Dense Ceramics using Sol-Gel and Ion-Exchange Process
Authors: Suda Seiichi , Ishii Hiroyuki , Kanamura Kiyoshi 
Published: April 2011

ABSTRACTLithium ionic conductor, (La, Li)TiO3, has synthesized with La/Li-TiO2 amorphous spheres that were obtained by sol-gel and ion-exchange method, and succeeding La3+/Li+ partial ion exchange. In this work, La /Li ion exchange conditions were mainly investigated in order to obtain dense (La, Li)TiO3 ceramics that have highly ionic conductivities. La +/Li+ ion exchange behavior was changed with ion-exchange solutions, and the Li/Ti ratio was increased with an increase in ethanol/water ratio in the solvent used for La3+/Li+ partial ion exchange. The use of an adequate ethanol/water ratio resulted in La/Li-TiO2 amorphous spheres with the composition of La/Li/Ti=0.54/0.34/1.00, and sintering of the spheres at 1200°C for 5 h in air led to dense (La, Li)TiO3 ceramics which exhibit the conductivity of 4.0 × 10-3 S cm-1 at 25°C.
Unusual Fast Cation Conduction in the High-Temperature Phase of Lithium Sodium Sulfate
Authors: Feldmann H. , Lechner R. E. , Wilmer D. 
Published: April 2011

ABSTRACTLithium sodium sulfate (LiNaSO4) belongs to a group of simple inorganic salts exhibiting fast-cation conducting high-temperature phases with rotationally disordered anions. The analysis of a combination of quasielastic neutron scattering and high-frequency (10 MHz to 60 GHz) conductivity measurements in the high-temperature phase of LiNaSO4 reveals an unusual cation conduction mechanism: the Haven ratio, HR = D*/Dσ, turns out to be considerably larger than one. This behavior, to our knowledge detected for the first time in a typical fast ion conductor, can be traced back to a charge correlation factor clearly smaller than unity, indicating that charge transport is less effective than tracer transport in this material.
Cation Transport and Surface Reconstruction in Lanthanum Doped Strontium Titanate at High Temperatures
Authors: Gömann Karsten , Borchardt Günter , Gunhold Anissa , Maus-Friedrichs Wolfgang , Lesage Bernard , Kaïtasov Odile , Baumann Horst 
Published: April 2011

ABSTRACTTracer diffusion experiments were carried out in synthetic air at 1573 K in SrTiO3(100) and (110) single crystals, which were either undoped or doped with up to 1 at.% La, respectively. Tracer sources of 139La and 142Nd were applied by ion implantation. The resulting depth profiles were measured by SIMS. The reconstruction of the surface was monitored ex-situ using microscopic and spectroscopic methods including SEM, EPMA, and AFM. The measured tracer diffusivities show no dependency on orientation. The tracer diffusion takes place via cation vacancies. Under oxidizing conditions the dopant is compensated by Sr vacancies. Hence the diffusion is increasing strongly with La concentration. The observed time dependency of the diffusivities may be related to a space charge layer postulated by the current defect chemistry model for donor doped SrTiO3. At high dopant concentrations annealing leads to segregation of bulk La to the surface. La is not significantly incorporated into the secondary crystallites at the surface which consist almost entirely of Sr and O.
A Study of the Oxygen Transport Kinetics in SrFeO3-x
Authors: Yoo Jiho , Jacobson Allan J. 
Published: April 2011

ABSTRACTExperimental results from electrical conductivity relaxation (ECR) measurements on SrFeO3-x are described. Values of Dchem and kchem were obtained by monitoring the variation of the time dependence of the electrical conductivity after an abrupt change in the oxygen partial pressure. Values for the oxygen ion and vacancy diffusion coefficients were calculated from the measured thermodynamic factors and compared with those of other compositions in the series La1-xSrxFeO3-x. The surface exchange coefficients, kchem and kex were also determined.
Phase Equilibria in the In2O3-WO3 System
Authors: Richard Annette P. , Edwards Doreen D. 
Published: April 2011

ABSTRACTThe subsolidus phase relationships in the In2O3-WO3 system at 800 – 1400°C were studied by X-ray diffraction. Two binary oxide phases – In2(WO4)3 and In6WO12 – are stable in air over the temperature range of 800 – 1200°C. Preferential volatilization of WO3 prevented the determination of phase equilibria above 1300°C.
Ionic Conductivity of the new Fluoride-Ion Conductor Casn2F6
Authors: Bell Michael F. , DéNés Georges , Zhu Zhimeng 
Published: April 2011

ABSTRACTMetastable CaSn2F6 has been prepared for the first time and characterized. It is a well crystalline material that leaches SnF2 in water to give the microcrystalline fluorite-type Ca1-xSnxF2 solid solution. In both materials, tin(II) is covalently bonded to fluorine, and thus carries a stereoactive non-bonding electronic pair. The electrical conductivity of CaSn2F6 was measured by the complex impedance method. The CaSn2F6 material was found to be a mixed conductor (τi = 0.50), with a F- conductivity a little below that of α-SnF2. On heating to 250°C, it decomposes irreversibly to give SnF2 and probably amorphous CaF2 (undetected).
Lithium electrochemical deintercalation from O2-LiCoO2: structural study and first principles calculations
Authors: Carlier D. , Van der Ven A. , Ceder G. , Croguennec L. , Ménétrier M. , Delmas C. 
Published: April 2011

ABSTRACTWe present a detailed study of the O2-LiCoO2 phase used as positive electrode in lithium batteries. This phase is a metastable form of LiCoO2 and is prepared by ionic exchange from P2-Na0.70CoO2. The O2-LiCoO2 system presents interesting fundamental problems as it exhibits several phase transformations upon lithium deintercalation that imply either CoO2 sheet gliding or lithium/vacancy ordering. Two unusual structures are observed: T#2 and O6. The T#2 phase was characterized by X-ray, neutron and electron diffraction, whereas the O6 phase was only characterized by XRD.In order to better understand the structures and the driving forces responsible for the phase transformations involved in lithium deintercalation, we combine our experimental study of this system with a theoretical approach. The voltage-composition curve at room temperature is calculated using Density Functional Theory combined with Monte Carlo simulations, and is qualitatively in good agreement with the experimental voltage curve over the complete lithium composition range. Pseudopotential and thermodynamic calculations both show that two tetrahedral sites have to be considered for Li in the T#2 structure. The calculated voltage curve thus exhibits a two-phase O2/T#2 region that indicates that this phase transformation is driven by the entropy maximization and not by a non-metal to metal transition. We also predict two ordered phases for Li1/4CoO2 (O2) and Li1/3CoO2 (O6) and show that the formation of the O6 phase is not related to Li staging or Co3+/Co4+ charge ordering.
Electrochemical intercalation of lithium in ternary metal molybdates MMoO4(M=Cu,Zn)
Authors: Buhrmester Th. , Leyzerovich N. N. , Bramnik K. G. , Ehrenberg H. , Fuess H. 
Published: April 2011

ABSTRACTTernary oxides with general formula MMoO4 (where M is a 3d-transitional metal) were characterized as cathode materials for lithium rechargeable batteries by galvanostatic charge-discharge technique and cyclic voltammetry. The significant capacity fading after the first cycle of lithium insertion/removal takes place for different copper molybdates (standard a-CuMoO4and high-pressure modification CuMoO4 –III) corresponding to the irreversible copper reduction and formation of Li2MoO4 during the first discharge. X-ray powder diffraction data reveal the decomposition of pristine ZnMoO4 by electrochemical reaction, lithium zink oxide with the NaCl-type structure and Li2MoO3 seem to be formed.
X-ray Absorption Spectroscopy study of lithium insertion mechanism in Li1.2V3O8
Authors: Bourgeon N. , Gaubicher J. , Guyomard D. , Ouvrard G. 
Published: April 2011

ABSTRACTX-ray absorption spectroscopy (XAS) measurements were performed to thoroughly understand lithium insertion mechanism in Li1.2V3O8. The evolution of the absorption pre-edge and edge corresponding to the local environment of the vanadium in the bulk has been examined by ex-si tu XAS measurement at the vanadium K edge, during the first discharge-charge cycle. The results show a regular and reversible evolution of the pre-edge intensity, the edge position and the vanadium environment toward nearly perfect VO6 octahedra.
The Electrochemistry of Germanium Nitride Versus Lithium
Authors: Pereira N. , Balasubramanian M. , Dupont L. , McBreen J. , Klein L. C. , Amatucci G. G. 
Published: April 2011

ABSTRACTGermanium nitride (Ge3N4) was examined as a potential negative electrode material for Li-ion batteries. The electrochemistry of Ge3N4 versus Li showed high reversible capacity (500mAh/g) and good capacity retention during cycling. A combination of ex-situ and in-situ x-ray diffraction (XRD), ex-situ transmission electron microscopy (TEM) and ex-situ selective area electron diffraction (SAED) analyses revealed evidence supporting the conversion of a layer of Ge3N4 crystal into an amorphous Li3N+LixGe nanocomposite during the first lithiation. The nanocomposite was electrochemically active via a reversible Li-Ge alloying reaction while a core of unreacted Ge3N4 crystal remained inactive. The lithium/metal nitride conversion reaction process was kinetically hindered resulting in limited capacity. Mechanical milling was found to improve the material capacity.
Impedance and Mott-Schottky Analysis of a Pr0.15Ce0.85O2-x Solid Solution
Authors: Bouchet R. , Knauth P. , Stefanik T. , Tuller H. L. 
Published: April 2011

ABSTRACTThe semiconductor properties of a praseodymium-cerium oxide solid solution with composition Pr0.15Ce0.85O2-x (PCO) were investigated by d.c. current-voltage and bias-dependent impedance measurements in aqueous solution. The solution data were compared with impedance values of dry cells in air. A Mott-Schottky analysis of the PCO-solution interface capacitance showed p-type semi conductivity, a flat-band potential Efb = (2.0 ± 0.1) V/NHE and an ionized acceptor density NA = 3 10 cm-3. Using these data, an electron hole mobility μh ∼ 10-5 cm2 V-1 s-1 was calculated pointing to a small polaron conduction mechanism with a hopping energy (Eh = 0.4 eV).
Improvements in Mechanical Behavior of SOFC Anodes
Authors: Kesler O. , Landingham R. L. 
Published: April 2011

ABSTRACTProcessing-induced residual stresses in the component layers of Solid Oxide Fuel Cells (SOFC's) can lead to fracture or to cell curvature which impedes stack assembly. Reducing or eliminating residual stresses to improve the mechanical behavior of the cells becomes increasingly important as the area of the cells is increased to increase the power of the fuel cell stack. Residual stresses in SOFC's result primarily from differential thermal expansion and sintering shrinkage between the component layers, such as the electrolyte and the anode support in a planar cell. This work investigates the impact of anode composition on each of these factors, with the ultimate goal of designing a flat, large-area cell. A range of anode compositions is investigated to determine the effect of different additives on the sintering behavior, and on the thermal and mechanical properties. Dilatometry, sintering shrinkage, scanning electron microscopy, and reduction studies are performed to correlate the microstructure, thermomechanical behavior, and composition. The experimental results are used to select an anode composition that leads to low overall cell curvature and improved mechanical behavior with respect to standard SOFC anode cermet materials.
Synthesis of Aurivillius Ceramics by the Polymerized Complex Method
Authors: Luisi Brian S. , Misture Scott T. 
Published: April 2011

ABSTRACTAurivillius phases of the type Bi2Sr2Nb2TiO12 and Bi1.6Pb0.4Sr2Nb2Ti1-xAlxO12 (0.0 ≤ × ≤ 0.8) were synthesized by the polymerized complex method involving an organometallic precursor. The effect of raising the pH of the solution was investigated through the addition of ammonium hydroxide. Infrared spectroscopy was taken at various points in the reaction to generate a mechanism. The IR data showed the formation of an ester as well as an amide with the addition of ammonium hydroxide. Pure Bi2Sr2Nb2TiO12 was formed after heat treatment for 5 hours at 900°C for the unaltered solution and 5 hours at 700°C when the solution pH was raised to 9.00. A solubility limit of aluminum was determined for Bi1.6Pb0.4Sr2Nb2Ti1-xAlxO12 when x ≥ 0.4. Conductivity measurements at 1123 K of Bi1.6Pb0.4Sr2Ti1-xAlxO12 range from 4.76 × 10-3 S•cm-1 at x = 0.8 to 1.74×10-4 S•cm-1 at x = 0.1.
A Performance Based, Multi-Process Cost Model for Solid Oxide Fuel Cells
Authors: Benson-Woodward Heather , Koslowske Mark , Kirchain Randolph , Bar-On Isa 
Published: April 2011

ABSTRACTCost effective high volume manufacture (HVM) is a major challenge to the success of solid oxide fuel cells (SOFCs). More than fifteen processing methods have been reported in the literature many of which could be used in various combinations to create the desired product characteristics. Modeling tools are needed to aid in the selection of the appropriate process combination prior to making expensive investment decisions.This paper describes the development of a multi-process cost model that permits the comparison of manufacturing cost for different processing combinations and various materials. Two specific processing methods are discussed, tape casting and screen printing.The results are compared with data and experience from the fuel cell and electronic packaging industries. Initial comparisons show good agreement with this experience base. Sensitivity of manufacturing costs to SOFC performance requirements such as maximum power density and operation temperature is investigated.
Optimization of a Carbon Composite Bipolar Plate for PEM Fuel Cells
Authors: Besmann Theodore M. , Henry John J. , Lara-Curzio Edgar , Klett James W. , Haack David , Butcher Ken 
Published: April 2011

ABSTRACTA carbon composite bipolar plate for PEM fuel cells has been developed that has high electrical conductivity, high strength, light weight, is impermeable, and has the potential for being produced at low cost. The plate is produced by slurry molding short carbon fibers into preform structures, molding features into the green body, and using chemical vapor infiltration to strengthen the material, give it high conductivity, and densify the surface to make it impermeable. Current efforts have focused on optimizing the fabrication process and characterizing prototypical components.
Granular State Effects on Wave Propagation
Authors: Hostler Stephen R. , Brennen Christopher E. 
Published: April 2011

ABSTRACTSound and pressure wave propagation in a granular material is of interest not only for its intrinsic and practical value, but also because it provides a non-intrusive means of probing the state of a granular material. By examining wave speeds and attenuation, insight can be gained into the nature of the contacts between the particles. In the present paper, wave speeds and attenuation rates are first examined for a static granular bed for a variety of system parameters including particle size, composition and the overburden of the material above the measuring transducers. Agitation of the bed is then introduced by shaking the material vertically. This causes the bed to transition from a static granular state to a vibrofluidized state. The dilation of the bed allows for relative particle motion and this has a significant effect on the measured wave speeds and attenuation. Further, the fluid-like characteristics of the agitated bed distort the force-chain framework through which the waves are thought to travel. The consequences of bed consolidation, a natural result of shaking, are also examined.