bluuebunny/crossref_metadata_2025 huggingface dataset:
Anion Intercalation and Anion Exchange in Bismuth Compounds
Authors: Tsuji Masamichi , Yamaguchi Makoto , Murao Satoshi
Published: April 2011

Bismuth nitrate basic, which chemical content is given by 4BiNO3(OH)2.BiO(OH), was studied for anion-intercalation or anion-exchange properties. A crystal structure of the bismuth nitrate basic has not been known. In the present study, its XRD pattern was indexed using a possible orthorhombic system having the lattice parameters of ao=3.021(1) nm, bo=3.029(1) nm and co=0.9572(3) nm. This compound was found to incorporate CH3COO-, halides and several oxyanions including CO32-. Incorporation of these anions by this solid was evidenced by broadening of infrared absorption band by NO3-, suggesting involvement with NO3- ions. Intercalation of CO32- by the bismuth nitrate basic in full extent yielded a bismutite represented by the chemical composition Bi2O2CO3. The bismuth nitrate basic will serve as a new host for anion-intercalation and anion-exchange.
Synthesis of Several Tungsten (VI) Complex Perovskites, Ba(BIII2/3W1/3)O3 (B = In, Y, Dy, Gd, Sm) by the Polymeric Precursors Method
Authors: Fuentes Antonio F. , Mendoza-Suarez Guillermo , Iván Escalante-García J. , Amador Ulises , Boulahya Khalid
Published: April 2011

We show in this work the usefulness of the polymeric precursors method to obtain several Ba(BIII2/3W1/3)O3 (B = In, Y, Dy, Gd, Sm) complex perovskites. Solid resins obtained from solution were treated at different temperatures and characterized by XRD and thermal analysis. BaCO3 and Ba(NO3)2 were the only crystalline species found below 500°C. Tungstates with different stoichiometry evolve from the powdered precursors as the temperature is raised. Formation of perovskite-like phases is evident in all five cases, above 1000°C. XRD results suggest also that trivalent ions do not participate in chemical reactions below that temperature since the presence of any binary phase containing them could be confirmed.
Surfactant Templated Assembly of Cubic Mesostructured Semiconductors Based on [Sn2Se6] 4- and Pt2+ in Single-Crystal Form.
Authors: Trikalitis Pantelis N. , Kanatzidis Mercouri G.
Published: April 2011

Mesostructured non-oxidic materials with cubic Ia-3d symmetry were prepared by linking [Sn2Se6] 4- clusters with Pt2+ in the presence of surfactant molecules. The use of long chain pyridinium-based surfactants (octadecyl- and eicosadecyl) afforded materials with exceptionally high cubic pore order and single-crystal particle morphology. By contrast trimethylammonium-based surfactants produced cubic mesostructured solids with inferior overall quality. We have also synthesized materials with significantly lower surfactant content by increasing the Pt2+:[Sn2Se6] 4- molar ratio, while maintaining the cubic pore symmetry. All materials are semiconductors with energy band-gap in the range 0.9<Eg<1.8 eV.
Photochemical Reactivity of Sr2Nb2O7 and Sr2Ta2O7 as a Function of Surface Orientation
Authors: Giocondi Jennifer L. , Zimbouski Ariana M. , Rohrer Gregory S.
Published: April 2011

Sr2Nb2O7 and Sr2Ta2O7 have a (110) layered perovskite structure and are efficient photolysis catalysts. Aqueous silver and lead cations were photochemically reduced and oxidized, respectively, on the surfaces of Sr2Nb2O7 and Sr2Ta2O7 crystals with a wide range of orientations. Atomic force microscopy has been used to observe the distribution of photochemically reduced and oxidized products and determine the orientation dependence of the reactivity. On surfaces with the same orientation, reaction products frequently had a non-uniform distribution. The reactivity of both compounds proved to be only weakly anisotropic, with the highest relative reactivity for both oxidation and reduction occurring for surfaces oriented between (010), (110), and (011). These low index orientations have structures similar to the ideal {110} and {100} planes in the perovskite structure, respectively. The relationship of the perovskite structure to the reactivity is discussed.
On the nature and structure of new MoVTeO and MoVTeNbO crystalline phases
Authors: García-González E. , López Nieto J. M. , Botella P. , Solsona B. , González-Calbet J.M.
Published: April 2011

New TeMoV and TeMo(V,Nb) bronze type phases have been obtained during the heat-treatment (600° C in N2) of the corresponding precursor mixture. Both mixed oxides seem to be structurally related to one of the crystalline phases proposed in Mo-V-Te-Nb-O catalysts. Chemical and microstructural characterization revealed the formation of an orthorhombically distorted cell deriving from a bronze type HTB structure, which does not behave as a bronze type structure in the chemical sense. Microstructural details responsible for the new unit cell are discussed in terms of tellurium location inside the hexagonal tunnels and based on the structural model proposed.
Orientation Dependence of the Photochemical Reactivity of BaTi4O9
Authors: Giocondi Jennifer L. , Samadzadeh Shahrzad , Rohrer Gregory S.
Published: April 2011

BaTi4O9 is a photocatalyst with a pentagonal prism tunnel structure. It has been hypothesized that the tunnels promote the separation of photogenerated carriers and, therefore, lead to the spatial separation of oxidation and reduction half reactions. This hypothesis has been tested by observing the distribution of reduced and oxidized reaction products on BaTi4O9 surfaces over a wide range of orientations. The surface orientations were determined by electron backscattered diffraction and atomic force microscopy was used to examine the structure of the surface both before and after the deposition of reaction products. Reduction products (Ag0) are distributed uniformly. The distribution of oxidation products (PbO2) is also not correlated to the surface orientation or to the orientation of the tunnels with respect to the surface. Based on these observations, we conclude that the tunnels in this structure do not separate photogenerated charge carriers and that this mechanism is not responsible for this compound's relatively high photocatalytic activity.
Disorderly conduct in Bi2Ln2Ti3O12 Aurivillius phases (Ln = La, Pr, Nd, Sm).
Authors: Hyatt Neil C. , Hriljac Joseph A.
Published: April 2011

The 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

We 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

The 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

The 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

The 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

New 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

Lithium 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

Lithium 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

Tracer 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

Experimental 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

The 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

Metastable 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

We 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

Ternary 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

X-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

Germanium 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

The 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

Processing-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

Aurivillius 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

Cost 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

A 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

Sound 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.
Maximum pore volume fraction and size for high fracture energy in porous bodies
Authors: Vandeperre Luc J. , Wang Jiaping , Clegg William J.
Published: April 2011

The fracture energy of a body containing pores might be expected to decrease linearly in proportion to the area fraction of material in the crack plane. However, there is experimental evidence that the fracture energy of porous materials only decreases when the pore volume fraction exceeds some critical value. To understand this, experiments have been conducted to directly observe the interaction between a growing crack with model distributions of pores. It is seen that cracks do not simply pass through the pores but spread around them causing the crack front to become curved and increase in length. For just two pores (or a line of pores) this is observed to continue until the crack has completely spread around the pores. It is observed that this increase in length increases the energy required for cracking, suggesting that the maximum fracture energy should rise with the volume fraction of pores. However, when this exceeds a certain value, the spreading crack front impinges on the pores ahead of the crack front before the maximum length of crack front due to bowing is reached. Beyond this critical volume of porosity, the resistance to fracture drops rapidly with porosity. Predictions of the relative fracture resistance of bodies containing spherical as well as cylindrical pores give good agreement with experimental observations, and are consistent with observations that the matrix fracture energy and pore size have little effect, provided the pores are much smaller than the sample.
Studies of residual stress, microcracks, hardness and microstructure of cold compacted metallic green bodies
Authors: Ericsson Torsten , Larsson Cecilia , Peng Ru Lin
Published: April 2011

The residual stresses have been measured by X-ray and neutron diffraction on PM green bodies manufactured by conventional and high speed compaction of iron powder with and without added copper and brass powder. Compressive residual stresses are present in a thin layer in both top and side surfaces. They are largest in the side surfaces due to plastic deformation of the surface material caused by the friction forces during ejection out of the die. In the interior of the green body residual stresses exist with certain region under compression (periferical regions) and other under tension (more central regions). It is unclear whether mixing iron powder with brass or copper powder leads to considerable phase stresses between the two phases.
Size and Density Separation in Granular Materials
Authors: MöBius Matthias , Nagel Sidney R. , Jaeger Heinrich M.
Published: April 2011

We review mechanisms leading to the separation of granular mixtures according to the size or density of the constituent particles. Besides a general overview, the focus of this article is on separation induced by vertical vibrations of the vessel holding the granular material, and specifically on recent results showing a density-dependence to the separation process. A convenient measure of the separation speed is the rise time of a larger “intruder particle” from some fixed initial depth to the free surface, where it will remain. Recent experiments have shown that for large intruder sizes the rise time depends on the density of the intruder particle. Furthermore, in three-dimensional systems we found that this density dependence is highly nonmonotonic. While there is no detailed theoretical understanding available yet, our experiments demonstrate that this surprising behavior is produced by interactions not only between the large intruder particle and the smaller particles of the surrounding granular bed, but also between the particles and the interstitial air.
The New Materials Science and Engineering Curriculum at the Ohio State University
Authors: Gupta P. K. , Anderson P. M. , Buchheit R. G. , Dregia S. A. , Lannutti J. J. , Mills M. J. , Snyder R. L.
Published: April 2011

A new Materials Science and Engineering (MSE) curriculum is in effect at the Ohio State University starting fall, 2002. This curriculum is composed of four parts:

1) General Education Core (required by the University of all undergraduates).

2) Engineering Core (required by the College of Engineering). This includes courses in English, Math, Physics, Chemistry, Statistics, Programming, Statics, and Stress Analysis.

3) Materials Science and Engineering Core (required by the MSE Department). It includes courses on Atomic Scale Structure, Microstructure and Characterization, Mechanical Behavior, Electrical Properties, Thermodynamics, Transport and Kinetics, Phase Diagrams, Phase Transformations, Modeling of Material Processes, Materials Selection, and Materials Performance).

4) MSE-Specialization in the senior year (required by the MSE Department). Novel features of the new curriculum include:

1) concentration in a specialized area of MSE in the senior year.

2) increased exposure to MSE courses in the second year.

3) increased industrial exposure.

4) redesigned laboratory courses.
An Upper Division General Education Course on Materials for Non-Engineering Students
Authors: Bahr D. F. , Norton M. G.
Published: April 2011

We present the structure of a new course which is designed to expose junior and senior level undergraduates in non-engineering fields to materials. Washington State University has a “General Education” requirement, which requires students to take a variety of courses including the area of sciences, humanities, and technology. We have developed this course to satisfy the requirement for technology for upper division students. The results of the enrollment over the past 3 years are presented: each semester more majors are taking the course, suggesting it is reaching an multidisciplinary audience. Comments from the students and plans for the future are discussed.
An Organic FET structure for unconventional substrates
Authors: Bonfiglio Annalisa , Mameli Fulvia , Sanna Ornella , Lutsen Laurence
Published: April 2011

A structure for organic TFTs suitable for being transferred on unusual substrates is described in each technological step. The proposed device consists in a “bottom-structure” assembled on a flexible and transparent insulating layer, without any substrate, with source and drain contacts on one side and the gate on the opposite side. The main advantage is to avoid the substrate because the insulator itself is able to support the whole structure. For this reason, application to any kind of substrates after the built-in process is possible.
A Protein Patterning Technique And Its Application In Bio-Inspired Self-Assembly
Authors: Guo D. , McNally H. , Pingle M. , Bergstrom D. , Bashir R.
Published: April 2011

Protein patterning techniques are crucial for the development of antibody-based biosensor and the study of controlled cell growth. This paper discusses a protein patterning technique based on microelectronic fabrication, DNA hybridization and biotin-streptavidin pair. A gold-on-silicon-dioxide substrate with micron size pattern was fabricated with photolithography and lift-off process. The average surface roughness of the gold pattern is 4.3 nm, measured by contact mode AFM. Thiol derivatized single stranded DNA was attached to the gold pattern surface by the chemical bonding between gold atom and sulfur atom. Surface attached DNA was then hybridized with a biotin conjugated complementary DNA sequence. Thus, the gold pattern was translated into a biotin pattern with similar resolution. Fluorescein conjugated streptavidin was patterned as demonstration. Fluorescence microscopy shows relative uniform streptavidin coverage of micron resolution and low background non-specific binding. The proposed protein patterning technique takes advantage of the high resolution of modern microelectronic fabrication. It has the potential of reaching sub-micron resolution. The biotin-streptavidin pair provides extremely specific and stable linking for protein immobilization. To show its application in biological inspired self-assembly, this technique was used successfully in the self-assembly of 20 nm streptavidin conjugated gold particles.
Self-aligned Split Gate Electrodes Fabricated on Suspended Carbon Nanotubes
Authors: Lee S.-B. , Robinson L. A. W. , Teo K. B. K. , Chhowalla M. , Amaratunga G. A. J. , Milne W. I. , Hasko D. G. , Ahmed H.
Published: April 2011

We describe the fabrication of self-aligned split gate electrodes on suspended multiwalled carbon nanotube structures. A suspended multiwalled carbon nanotube structure was used as an evaporation mask for the deposition of metal electrodes resulting in the formation of discontinuous wire deposition. The metal deposits on the nanotubes are removed with lift-off due to the poor adhesion of metal to the nanotube surface. Using Al sacrificial layers, it was possible to fabricate self-aligned contact electrodes and control electrodes nanometers from the suspended carbon nanotubes with a single lithography step. It was also shown that the fabrication technique may also be used to form nano-gaped contact electrodes. The technique should prove useful for the fabrication of nano-electromechanical systems.
Material Issues of Low Temperature Co-fired Ceramic (LTCC) Fine Pitch Chip Scale Package (CSP) Designs
Authors: Owens Megan M. , Soucy Joseph W. , Marinis Thomas F. , Bruff Kevin A. , Clausen Henry G.
Published: April 2011

LTCC substrates for fine pitch (1.0 mm and 0.8 mm) CSP applications have been designed, fabricated, and assembled. The assembly process, including ball grid array (BGA) solder ball attach, die mount, wire bond, and glob top is described. The material and physical design interaction issues that emerged during development are discussed.

The initial CSP design was conventional, with co-fired yellow gold (Au) vias and capture pads and post-fired solderable gold (PtPdAu) pads for solder ball attachment. Because LTCC tape shrinks during co-fire, solder pads were applied post co-fire to ensure proper mating with existing test fixtures and to provide the best alignment relative to the CSP body. Solder pad to capture pad misalignment was visible following solder pad firing. After CSP attachment to a test board, electrical tests revealed opens. Investigation led to the following conclusions. The decreased solder pad diameter necessary to accommodate the fine pitch design was significant relative to the area allocated for the underlying via and capture pad. Misalignment that would have been hidden under larger solder pads was exposed. Even when the capture pad surface was not visibly exposed, the offset solder pad meant less material between the capture pad and the solder ball, less of a barrier to solder leaching. Solder leaching into the yellow gold, observed after CSP removal from the test board, was the cause of the electrical disconnects. In the second design, the capture pad was eliminated in order to discourage leaching by reducing the volume of yellow gold available to alloy with the solder pad during co-fire. Reflow operations still resulted in leached solder pads. A third design replaced the first-layer via yellow gold with a solderable gold. This design proved to be robust.

While developing designs and fabricating these prototypes, it was noted that all ball failures consistently occurred between the solder pad and the LTCC substrate. To investigate adhesion using different metallizations, shear tests were performed on LTCC substrates with either post-fired solder pads or co-fired pads. To investigate how the substrate material affects adhesion, alumina CSPs were also sheared. Shear test results are presented.
In-Plane Ferroelectricity in Strontium Titanate Thin Films
Authors: Astafiev K. F. , Sherman V. O. , Cantoni M. , Tagantsev A. K. , Setter N. , Petrov P. K. , Kaydanova T. , Ginley D. S.
Published: April 2011

The results of structural and electrical characterizations of SrTiO3 thin films deposited onto LaAlO3 substrates by pulsed laser deposition technique are presented. The appearance of the ferroelectric phase in these films has been experimentally documented, the transition temperature being in the range of 90–120K. The hysteresis loops have been monitored in a wide temperature range by using thin film planar capacitors, the driving field being predominantly in the plane of the film. The switching properties of the films has been studied at low temperatures (∼25K) and well saturated loops have been observed with relatively low coercive field (<6kV/cm for 10μm gap). The presence of the imprint phenomenon has been also found at low temperatures.

The microstructure of the investigated SrTiO3 thin films has been studied by using a high resolution transmission electron microscope (TEM). It has been found that the annealed and as-deposited thin films, being of the same composition, have quite different microstructures. The difference observed in the polarization response of the films is related to that in their microstructure.
Theoretical and Experimental Study of Barium Zinc-Cadmium Tantalate-based Microwave Dielectrics
Authors: Liu Shaojun , Van Schilfgaarde Mark , Sun Jian , Badd Louisa , Smith David , Petrovixc Novak S. , Taylor R. , Newman N.
Published: April 2011

Single-phase Ba(Cd1/3Ta2/3)O3 ceramics have been produced using conventional powder processing methods. In our initial investigations, 2wt% ZnO powder was added to act as a sintering aid since a high-density ceramic was not formed from solid-state diffusion alone. The resulting Ba(Cd0.327Zn0.006Ta2/3)O3 material sintered at 1550° C exhibits a dielectric constant of ∼33 and loss tangent of <5×10−5 at 2 GHz. In our more recent work, we have used boron as a sintering aid to facilitate sintering at temperatures as low as 1300° C, enhance the structural quality and improve the microwave properties of Ba(Cd1/3Ta2/3)O3 dielectrics. TEM results indicate that the liquid sintering mechanism is an important factor for boron concentrations exceeding 0.5wt%, while a point defect mechanism plays the dominant role at lower boron concentrations. The presence of superstructure peaks and splitting of the (220) and (214) peaks in X-ray diffraction spectra are direct evidence for the distortion from cubic symmetry as a result of Cd and Ta ordering on the B-site.

Ab-initio electronic structure calculations within the local density functional approximation have been used to give insight into the unusual properties of this class of materials. In both Ba(Zn1/3Ta2/3)O3 and Ba(Cd/3Ta2/3)O3, the conduction band maximum and valence band minimum are composed of mostly weakly itinerant Ta 5d-and Zn-3d/Cd-4d levels, respectively. The covalent nature of the directional d-electron bonding in these high-Z oxides plays an important role in producing a more rigid lattice with higher melting points and enhanced phonon energies, and possibly inherently lower intrinsic microwave loss than comparable ionic materials.
A New Dielectric Material System of xLa(Mg1/2Ti1/2) O3−(1−X) CaTiO3 at Microvave Frequency
Authors: Chen Yuan-Bin , Huang Cheng-Liang , Row Che-Win
Published: April 2011

The dielectric properties and the microstructures of xLa(Mg1/2Ti1/2)O3−(1−x)CaTiO3 ceramics with B2O3 additions (0.25wt%) prepared with conventional solid-state route have been investigated. Doping with B2O3 (0.25wt%) can effectively promote the densification and the dielectric properties of xLa(Mg1/2Ti1/2)O3−(1−x)CaTiO3 ceramics. It is found that xLa(Mg1/2Ti1/2)O3−(1−x)CaTiO3 ceramics can be sintered at 1400°C due to the liquid phase effect of B2O3 addition observed by Scanning Electronic Microscopy. At 1425°C, 0.5La(Mg1/2Ti1/2)O3−0.5CaTiO3 ceramics with 0.25 wt% B2O3 addition possesses a dielectric constant (εr) of 43, a Q×f value of 24470 (at 8GHz) and a temperature coefficients of resonant frequency (τf) of -8.94 ppm/°C. As an increasing the content of La(Mg1/2Ti1/2)O3, the highest Q×f value of 30824(GHz) could be achieved for X=0.7.
Rapid Prototype Fabrication of Custom Chip Scale Packages
Authors: Owens Megan M. , Soucy Joseph W. , Marinis Thomas F. , Clausen Henry G.
Published: April 2011

Many new electronic systems require very high-density packaging to meet system volume and weight constraints. The Chip Scale Package (CSP) is often used to meet this need. However, the limited commercial availability of die in CSP form frequently drives system designers to pursue custom CSP fabrication. Long lead times and manufacturers' reluctance to run small batches typically limit the use of custom CSPs to high volume applications. This paper presents an approach for the rapid prototype of Low Temperature Co-fired Ceramic (LTCC) CSPs.

Integral to the approach is the concept of using a small family of generic substrate designs to build a large variety of CSPs. The generic substrates may be fabricated and kept on hand until a CSP application need arises. When it does, a 12-to-16-week industry-typical lead time does not apply; the CSP may be fabricated rapidly, on site. Fabrication consists of simply singulating the substrate, populating the solder ball pads, mounting and wire bonding the die, encapsulating the substrate surface, and laser marking the assembly. The lead time may be slashed from several months to just a few days.

The family of substrate designs will be described. The substrates, with gold-based interconnects, have standard JEDEC Ball Grid Array (BGA) footprints of either 0.8 mm or 1.0 mm pitch. Substrates have a top surface metallization scheme of either a large central die bond pad surrounded by a number of peripheral bond sites for wire bonds, or a blanket metallization layer that may be patterned, via photolithography, to accommodate a specific application at the time of need. The die pad design is used for CSPs with a single die, while the blanket metallization design is patterned for hybrid or multi-die applications. The design approach, custom photopatterning and gold etch, and assembly processes are presented.
Dielectric Properties of BaTiO3 Based Ceramics Prepared from Nano-powders
Authors: Wang Xiao-Hui , Chen Ren-Zheng , Gui Zhi-Lun , Li Long-Tu
Published: April 2011

In this paper, the BaTiO3 nanoceramics have been fabricated by pressureless sintering for the first time. High purity BaTiO3 powders in nano-size of 50∼80nm synthesized by wet chemical method were used to fabricate nanoceramics. The addition of an appropriate amount of Nb2O5 and Co3O4 was found to suppress the grain growth, which is normally encountered in the conventional pressless sintering. The effects of Nb2O5 and Co3O4 on the phase structure, microstructure and dielectric properties of the sintered ceramics were investigated. The BaTiO3 ceramics with the average grain size less than 100nm were achieved after sintering below 1220°C with dielectric constant up to 2000 at room temperature, which is of cubic structure and meets the requirement of X7R specification.