bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical and Thermophysical Properties of Silicon Nitride Thin Films at High Temperatures Using In-Situ Mems Temperature Sensors
Authors: Nieva Patricia , Tada Haruna , Zavracky Paul , Adams George , Miaoulis Ioannis , Wong Peter
Published: April 2011

The optimization of microelectronic devices and Microelectromechanical Systems (MEMS) technology depends on the knowledge of the mechanical and thermophysical properties of the thin film materials used to fabricate them. The thickness, stoichiometry, structure and thermal history can affect the properties of thin films causing their mechanical and thermophysical properties to diverge from bulk values. Moreover, it is known that the mechanical and thermophysical properties of thin films vary considerably at different temperatures. Bulk properties of semiconductors have been characterized over a wide range of temperatures; however there is limited information on thin film properties of silicon-based compounds such as silicon nitride, specially at high temperatures. In our work, MEMS devices designed to record the localized maximum temperature during high temperature thermal processes, which we call Breaking T-MEMS, will be presented as a way to determine some of the mechanical properties (Young's modulus and fracture strength) and thermophysical properties (coefficient of thermal expansion) of silicon-rich nitride thin films at high temperatures.

The Breaking T-MEMS device consists of a thin film bridge suspended over a substrate. During testing, the devices are thermally loaded in tension by heating the sample. The low coefficient of thermal expansion of the film relative to that of the substrate causes the thin film bridge to break at a specific temperature. Through a combination of indirect experimental measurements, analytical expressions, numerical and statistical analysis, and if the experiments are conducted using at least two different substrates of known temperaturedependent coefficients of thermal expansion, some of the material properties of the film can be calculated from the breaking temperatures of various devices. The two candidate materials for the substrate are silicon and aluminum oxide (sapphire).
Cation Size and Disorder Effects in Conducting Perovskite Oxides
Authors: Attifield J. Paul , Kharlanov Andrei L. , McAllister Judith A. , Rodriguez-Martinez Lide M.
Published: April 2011

The electronic and magnetic properties of ATO3 and related perovskites (A is a mixture of lanthanide Ln3+ and alkaline earth M2+ cations; T is a transition metal) are very sensitive to the A site composition. The importance of doping effects controlled by the Ln3+/M2+ ratio is well-known, but the other lattice effects controlled by the sizes of these cations are less well understood. A simple approach making use of the mean (first moment) and the variance (second moment) in the A cation distribution has been applied to the metal-insulator transition temperature in colossal magnetoresistance AMnO3 perovskites and to the critical temperature in A2CuO4 and LnBa2Cu3O7-δ superconductors. Series of compositions prepared with a constant doping level and mean A cation radius show a linear decrease of the transition temperature Tt with the A cation size variance σ2. The rate of decrease -dTt/dσ2 is found to lie in the range 1,000-30,000 KÅ-2. The orthorhombic-tetra onal structural transition in the A2CuO4 materials is found to show a linear increase with σ2. A pair of quadratic relationships for the mean size and size variance effects are proposed to be the result of changing strain energies that give rise to these effects.
Preparation and Characterization of Sodium and Iron-Containing Diopside Crystal by Several Methods from Solution
Authors: Iwata Noriyuki , Yokoyama Masashi , Ishinabe Akiko , Tsuchiya Tatsunori , Tsunakawa Sukenari , Lee Geun-Hyoung
Published: April 2011

Diopside (CaMgSi2O6) crystals were synthesized mainly by several methods from solution. Sol-gel methods and coprecipitation procedures were carried out using the metal chlorides, nitrates and TEOS as the starting materials. The diopsides obtained from the solutions, in which MgCl2 was used as one of the the starting reagents, showed the single phase diopside XRD patterns and fairly high mechnical strength. Sodium carbonate and iron nitrate were added to the starting solutions in order to examine the morphological effects of these extra elements. Resulted XRD patterns showed the small 2 θ shifts from the pure diopside patterns. The distribution maps of each elements were obtained by EPMA.

To confirm the bioactivity of these compounds, the end products pellets were immersed in the SBF. The apatite layer formations were inspected by XRD and SEM.
Non Trivial Processes for Obtaining Bi-Based High Tc Superconductors
Authors: Cloots R. , Ausloos M.
Published: April 2011

Dysprosium doped Bi-based 2212 ceramics were synthesized by a melt-texturing growth process in a 1.2T magnetic field, applied perpendicularly to the main axis of a cylindrically shaped sample. The materials were characterized by X-ray diffraction, optical and scanning electron microscopy and energy dispersive X-ray analyses. The texturing process was optimized with respect to the sample electrical resistivity and AC magnetic susceptibility.
Thin Film Synthesis of Copper-Based Perovskites Having Two-Dimensional Cation Order: (La0.8Ba0.2CuO2.6±x) (AECuO2)n Superlattices
Authors: Salvador P.A. , Doan T-D. , Mercey B. , Raveau B.
Published: April 2011

Using a multi-target pulsed laser deposition (PLD) process we synthesized superlattices in the (La0.8Ba0.2CuO2.6±x)m(AECuO2)n system, where AE = Ca or Sr, and m and n were varied. Owing to the sequential deposition process, two-dimensional order is obtained on the perovskite A-sites in the superlattice structures, as evidenced by X-ray diffraction for the materials where AE = Sr. However, when AE = Ca, the films were unstable. Structural units of CaCuO2 could be incorporated into the superlattices by containing them between layers of SrCuO2: (SrCuO2)l(CaCuO2)m(SrCuO2)l(La0.8Ba0.2CuO2.6±x)n. The stability and structural characteristics of particular stacking sequences are discussed with respect to their chemical preferences and are compared to bulk materials of similar stoichiometries, i.e., the (La,AE)CuO3-x system. The latter materials do not exhibit two-dimensional cation-order. Resistance measurements of as-synthesized and post-annealed materials are also discussed.
Phase Segregation in Manganese Perovskites
Authors: Radaelli P.G. , Argyriou D.N. , Cox D.E. , Capogna L. , Casalta H. , Andersen K. , Cheong S-W. , Mitchell J.F. , Marezio M.
Published: April 2011

The structural, magnetic and transport phase diagrams of the manganese perovskites (general formula: A1-xA'xMnO3) are characterised by a variety of exotic phenomena, including high-temperature polaronic behaviour, charge, orbital and magnetic ordering and colossal magnetoresistance (CMR). These properties can be “tuned” by changing the doping level x, the electronic bandwidth (through the average A-site ionic radius, ), and the A-site disorder, and are believed to be a manifestation of the underlying competition between electron-lattice coupling and double exchange. Usually, at low temperatures, one of these two interactions is dominant, resulting in a homogeneous ground state, which is either a metallic ferromagnet or a charge-ordered insulator. We have recently found, however, that, for special points in the phase diagram (x ~ 0.3,, ~ 1.18 Å), the competition can be preserved down to low temperatures, resulting in an inhomogeneous ground state at the microscopic level. This unusual state is characterised by the coexistence of charge-ordered and metallic domains, which are intertwined over a variety of length-scales, and appear to show spin-glass-like dynamics. Upon application of an external field (magnetic field, pressure or even x-rays), the domains grow to macroscopic sizes, resulting in phase segregation. We speculate that the evolution of the local magnetic and crystal structures during this phase segregation process may parallel those occurring, at much higher temperatures, for compounds displaying CMR behaviour at the paramagnetic-toferromagnetic transition. Very recently, it has been suggested that the charge-ordered state, which is stable for higher values of the Mn oxidation state (x ≥ 0.5), may also be associated with modulated mesoscopic phase segregation, in the form of “stripes”. This hypothesis will be discussed in the light of recent x-ray synchrotron and neutron diffraction data on the crystallographic and magnetic modulation in La0.33Ca0.67MnO3
Epitaxial Growth of Rare-Earth Gallates on Single-Crystal Oxide Substrates
Authors: Morrell Jonathan S. , Xue Ziling B. , Specht Eliot D. , Beach David B.
Published: April 2011

Epitaxial films of lanthanum gallate, praseodymium gallate, and neodymium gallate were prepared on [100] strontium titanate and [100] lanthanum aluminate single crystal substrates using solution techniques. The solutions employed were mixed-metal methoxyethoxides in 2-methoxyethanol. Films were prepared by spin-coating with a partially hydrolyzed solution, followed by firing at 850 °C for 20 minutes in air. Theta/2-theta scans revealed only [h00] reflections and omega scans (rocking curves) indicated good out-of-plane orientation. Pole figures and phi scans revealed good in-plane orientation and a [100] || [100] epitaxial relationship between the film and the substrate.
Hydrogen-Bonding and Phase Transitions in Proton-Conducting Solid Acids
Authors: Haile Sossina M.
Published: April 2011

From an investigation of the structures and electrical properties of compounds in the CsHSO4 - CsH2PO4 system, a simple model is presented for predicting whether or not a solid acid will undergo a structural transition to a disordered, superprotonic phase. Such a transition was measured in ß-Cs3(HSO4)2(H2-x(SxP1-x)O4), α-Cs3(HSO4)2(H2PO4) and Cs2(HSO4)(H2PO4), but not CsH2PO4. It is proposed that entropy drives any solid acid to a high-temperature structure in which the oxygen atoms participate equally in forming hydrogen bonds. If the H:XO4 ratio is not precisely 2:1, such chemical equivalence of oxygen atoms can only be achieved if the structure transforms to a state in which proton occupancies at hydrogen bonds are less than one and/or oxygen site occupancies are less than one. This disorder simultaneously leads to fast proton transport in the high-temperature phase, and thus superprotonic conductivity.
Crystal Chemistry of Y2(ZrySn1-y)2O7Pyrochlore Solid Solutions and its Relation to Fast-Ion Conduction
Authors: Ku Esther M. , Yeo Evangeline M.E. , Wuensch Bernhardt J.
Published: April 2011

Pyrochlore oxides, A2B2O7, are of interest as fuel cell materials and sensors because, with suitable doping, they may be fast-ion conducting or p- or n-type electronic conductors. An earlier analysis of Y2(ZryTi1-y)2O7solid solutions showed that substitution of the larger Zr ion for Ti induced progressive disorder in both the cation and anion arrays causing a 103increase in oxygen ion conductivity. In contrast, Y2(SnyTi1-y)2O7solid solutions remained essentially fully ordered over their entire range of composition even though the range of average radii of the cation species in the B site overlapped to a considerable degree with those of the (ZryTi1-y) materials. The present work used Rietveld analysis of both neutron and x-ray powder profiles to examine Y2(ZrySn1-y)2O7compositions along the third leg of the pseudo-ternary system: solid solutions between the stannate, with strong tendency to remain ordered, and the zirconate which has predilection toward complete disorder. Progressive disorder in the oxygen ion array was again observed with increasing y. Mixing between cation sites was found to progress at a rate independent of anion disordering. The behavior was very similar to Y2(ZryTi1-y)2O7, suggesting that the differing behavior of the three systems is due to the ability of Zr to readily enter the eight-coordinated A site.
Effect of Co3+Ion on Metal-Insulator Transition in (La0.1Ca0.9)(Mn1-xCox)O3
Authors: Taguchi Hideki
Published: April 2011

Orthorhombic perovskite-type (La0.1Ca0.9)(Mn1-xCox)O3was synthesized in the range 0.00 ≤x≤ 0.08. The Rietveld analysis indicates that the (Mn, Co)-O(1 and 2) distances are independent of the composition (x). Measurements of the electrical resistivity (ρ) and the Seebeck coefficient (α) indicate that (La0.1Ca0.9)(Mn1-xCox)O3is an n-type semiconductor at the low temperature. At the high temperature, (La0.1Ca0.9)(Mn1-xCox)O3exhibits a metal-insulator transition in the range 0.0 ≤x≤ 0.04. The metal-insulator transition temperature (Tt) increases with increasing the Co3+ion content, whiledρ/dTin the metallic region decreases with increasing the Co3+ion content. The variation of Eaand T+is explained by the difference in the electronegativity between Mn and Co atoms. The variation ofdρ/dTin the metallic region is explained by the increase in the collective o bond.
Reactivity and Stability of Superionics MSnF4 at High Temperature in Various Media
Authors: Dénès Georges , Madamba M. Cecilia , Muntasar Abdualhafeed
Published: April 2011

Superionic MSnF4 are the highest performance fluoride ion conductors, with PbSnF4 being the best. Prototypes of devices using PbSnF4 have been constructed and tested. Since the fluoride ion mobility is thermally activated, some devices might be used more efficiently above ambient temperature. Therefore, it is of prime importance that the stability of these materials be tested under potential conditions of use, since thermal degradation and phase transitions are likely to alter the conducting properties. Tetragonal SrSnF4, α-PbSnF4 and BaSnF4, and orthorhombic o-PbSnF4, are stable at ambient conditions, even in air. However, all undergo significant deterioration when heated in air: the color changes from white to yellowish, and tin hydrolysis and oxidation takes place. They are much more stable under inert conditions (nitrogen or argon). However, PbSnF4 undergoes several phase transitions at high temperatures: o to α starting at ca. 100°C, α to β (reversible, but the reverse reaction is very sluggish) starting at 250°C, β to γ (reversible) at 390°C. β-PbSnF4 can be quenched to ambient temperature and is metastable for long times, however, eventually it starts changing to stable α-PbSnF4 and this change is uncontrollable and is faster above ambient temperature. Microcrystalline μγ-PbSnF4, obtained by ball milling any other phase of PbSnF4, gives rapidly a-PbSnF4 at 200°C. In addition, for all MSnF4, hydrolysis of the Sn-F bonds to Sn-O occurs with traces of moisture.
Reactivity of SnF2 with Fluorite Type MF2 Versus M: Synthesis of High Performance Fluoride Ion Conductors
Authors: Dénès Georges , Madamba M. Cecilia , Muntasar Abdualhafeed
Published: April 2011

The fluorite type MF2 materials react at high temperature with tin(II) fluoride SnF2 in the 1: 1 stoichiometry to give high performance fluoride ion conductors MSnF4. However, the reaction takes place only for the largest M cations (M = Sr, Pb and Ba). For the others (M = Cd and Ca), no reaction takes place. Furthermore, when the reaction occurs, it is observed that the reactivity of SnF2 with MF2 is highly dependent on M. The reaction with PbF2 is the easiest; it is complete at 250°C, whereas 500°C is required with SrF2 and BaF2. In addition, with SrF2, an incomplete reaction is observed very often. Moreover, PbF2 and SnF2 fully react at other stoichiometries to give other materials, whereas SrF2 and BaF2 do not, and with CdF2 and CaF2 not even MSnF4 is formed. A structural analysis based on bond angles and using the size of the M2+ cations is used in an attempt to explain the lack of reactivity for the smallest M2+ cations and the poor reactivity of SrF2. However, the relative cationic sizes cannot explain all the trends, inclusing the exceptionally high reactivity of PbF2 (lower reaction temperature, much richer source of materials). An explanation based on the electronic structure of tin(II) and lead(II) has been developped in order to account for the results.
Synthesis, Structure and Magnetic Properties of the Group IV Ternary Nitrides, AMN2 (A = Alkaline Earth Metal, M = Transition Metal)
Authors: Gregory Duncan H. , Barker Marten G. , Siddons Daniel J. , Edwards Peter P. , Slaski Marcin
Published: April 2011

The ternary transition metal nitrides of general formulation AMN2 (A = alkaline earth metal, M = transition metal) have been systematically studied. These compounds have been synthesised by high temperature solid state reaction from their component binary nitrides in sealed systems. The structures of these materials have been determined by powder X-ray diffraction (PXD) and two layered structure-types (α-NaFeO2-type and KCoO2-type) have been observed, thus far. Intriguingly, magnetic measurements performed on nitride samples indicate they may not be diamagnetic (d = 0, S = 0) as their nominal stoichiometry suggests.
Synthesis of Silicon Nitride Whiskers by Microwave Heating
Authors: Gedevanishvili S. , Cherian K. , Agrawal D. , Roy R.
Published: April 2011

Whiskers of silicon nitride were synthesized by heating silicon powder compacts, silicon single crystal and polycrystalline silicon in microwave in the presence of flowing forming gas or nitrogen. Various gas compositions and form of silicon used resulted in different whisker morphologies. Silicon powder as starting material leads to the formation of needle-like whiskers while silicon single crystal and polycrystalline silicon led to the formation of wool-like and web-like structures respectively. Length of the whiskers apparently depends on the holding time at the optimum temperature ~1350°C; whiskers up to 250 micrometers in length may be grown in 30 minutes. Microstructural data suggest that the silicon nitride whiskers form through gas-solid reaction and vapor-solid mechanism.
Lone Pair Interactions in Zintl Phases and Intermetallic Compounds: Influence on Electronic Properties in Stannides and Plumbides
Authors: Fässler Thomas F.
Published: April 2011

The phases K6Sn23Bi2, K6Sn25, NaSn5, BaSn3, BaSn5, and K5Pb24 depict the structural transition from Zintl phases with localized chemical bonds to typical intermetallic compounds which may even have superconducting properties. The question of the nature of the chemical bond in these compounds is studied with the help of quantum mechanical calculations. Tight binding band structure calculations and real space representations using the Electron Localization Function (ELF) show that free electron pairs play a crucial role for the description of the chemical bond in polar intermetallic compounds. Interactions between lone pairs have a dominant influence on the electronic structures. The coincident appearance of quasi-molecular localized states in form of lone pairs and disperse delocalized bands at the Fermi level EF is discussed with respect to a ‘chemical view’ of the superconductivity observed for BaSn3, BaSn5, and K5Pb24.
Cryosol Synthesis of Nanocomposite Materials
Authors: Kalinin S.V. , Vertegel A.A. , Tretyakov Yu.D.
Published: April 2011

Formation of nanocomposites in the course of hydrolytic polycondensation processes is investigated. Depending on the order of particle-formation and matrix-formation steps three possible synthetic strategies are studied. The freeze-drying technique is used for dehydration of the gel precursor to avoid the redistribution of a soluble component. Heat treatment or chemical modification of the cryogel yields the desired nanomaterial.
Robust Microporous Molecular Frameworks Which Retain Structural Integrity Upon Template Loss
Authors: Kepert C. J. , Rosseinsky M. J. , Hesek D. , Beer P. D.
Published: April 2011

Retention of the void space upon loss of the solvent template is directly demonstrated using single-crystal X-ray diffraction for molecular frameworks constructed using both hydrogen and co-ordinate bonds. While the co-ordination polymer remains rigid upon desolvation, the extra flexibility in the hydrogen-bonded framework, due both to the large number of redundant hydrogen-bonding donor and acceptor groups and the possibility of significant φ-φ stacking interactions within the framework, lead to a significant structural and symmetry change while retaining significant void volume. Molecular modelling techniques are used to understand and predict the guest uptake chemistry of these host frameworks.
Graphite Intercalation Compounds Prepared in Hydrofluoric Acid
Authors: Zhang X. , Lerner M.M.
Published: April 2011

The graphite intercalation compounds CxC8F17SO3 · yF and CxN(SO2CF3)2 are readily prepared under ambient conditions in 48 % hydrofluoric acid, using the oxidant K2MnF6. The product compositions are evaluated by mass uptake, TGA, and elemental analysis. PXRD peak position and peak width analyses indicate that the stable product CxC8F17SO3 · yF is obtained after 50 h. (x ≅ 18, y ≅ 4) and is comprised of a solid solution of stage 2 and 3. This material can be obtained within 1 h. at 50 °C. The addition of up to 83 vol. % conc. HNO3 or 17 % fuming H2SO4 produces a stage 2 intercalation compound within hours. Stage 2 CxN(SO2CF3)2 (x = 37) is obtained within 15 minutes under ambient condition in HF. The anion orientations for these GICs are evaluated by structural refinement. Larger anions containing –SO2CnF2n+1 substitutents can also be intercalated, although the reaction rates are very slow.
Study of The Hydrothermal Synthesis of Gallium Phosphates Using in Situ Time-Resolved X-Ray Diffraction
Authors: Walton R.I. , Loiseau T. , Francis R.J. , O'Hare D. , Férey G.
Published: April 2011

The hydrothermal crystallisation (130-180 °C) of three-dimensional open-framework gallium and aluminium oxyfluoro-phosphates with the ULM-3 and ULM-4 structures have been studied in situ for the first time. The in situ energy-dispersive X-ray diffraction method has allowed the formation of the crystalline products to be observed under hydrothermal conditions The integrated areas of the strongest Bragg reflections has allowed quantitative kinetic data to be extracted. The effect of temperature, phosphorus source, templating agent have been investigated. The nature of phosphorus source in the reaction mixture has been found to affect dramatically the course of reaction for certain combinations of amine and temperature. Previously unobserved transient crystalline phases have been seen during the production of ULM-3 gallium phosphates when P2O5 or polyphosphoric acid are used. The formation of these intermediates affects the kinetics of product growth. In the case of the aluminium ULM-3 materials reaction always proceeds via a crystalline intermediate whatever phosphorus source is used. The ULM-4 framework materials are found to always crystallise directly with no evidence for any intermediates. Kinetic data for each system have been modelled using standard solid-state chemistry expressions, and these calculations indicate the reactions to be diffusion controlled.
Redox Processes in Polynary Copper Oxides and Copper Oxide / Mesoporous Silica Composites
Authors: Reller A. , Ebbinghaus S. , Köhn R. , Fröba M. , Sazama U. , Fortunato P.
Published: April 2011

Dynamic redox processes in different complex copper oxides and oxide / mesoporous silica composites are characterized. In the spinel-type CuxMn3.xO4 the atomic and electronic structures are described with respect to the reversible process Cu2+ + Mn3+ ⇒ Cu3+ + Mn4+, the crucial dynamic equilibrium for the catalytic oxidation of CO to CO2 at ambient temperatures. A comparison with the perovskite-type LaCu1-xMnxO3-δ is presented. In the K2NiF4-type La2-xSrxCu1-yRuyO4-δ the electronic structure is characterized with respect to the equilibrium Cu2+ + Ru5+ ⇒ Cu3+ + Ru4+. Analogous redox processes are characterized in composite compounds made up of copper oxides inserted in mesoporous MCM-type silica. Due to their structural order in the nanoscopic range, the investigation of these materials required multiple, complementary characterization methods, i.e. X-ray diffractometry, thermal analysis, scanning and transmission electron microscopy, magnetic measurements, XPS, and particularly X-ray absorption spectroscopy (EXAFS / XANES) measurements.
The Hydrothermal Synthesis of KzMnO2 in the Presence of Citric Acid
Authors: Sharma Pramod K. , Moore Gregory J. , Whittingham M. Stanley
Published: April 2011

KxMnO2 exhibits a layered structure that provides attractive properties as a cathode material for secondary Li batteries. Therefore, in the present study, our attention was paid to the hydrothermal preparation of highly homogenous KxMnO2 in presence of citric acid. Out X-ray diffraction and SEM studies indicated that the final product markedly change the phase and morphology on vary the concentration of citric acid. The prepared products have also studied with the help of TGA and DTA. EDS and DCP made the chemical analysis of the compounds. The impedance data of the materials were explained in terms of the compounds formed.
First Principles Calculations for Lithiated Manganese Oxides
Authors: Prasad R. , Benedek R. , Thackeray M. M. , Wills J. M. , Yang L. H.
Published: April 2011

First principles calculations within the local-spin-density-functional theory (LSDFT) framework are presented of densities of electronic states for MnO, LiMnO2 in the monoclinic and orthorhombic structures, cubic LiMn204 spinel and λ-MnO2 (delithiated spinel), all in antiferromagnetic spin configurations. The changes in energy spectra as the Mn oxidation state varies between 2+ and 4+ are illustrated. Preliminary calculations for Co-doped LiMnO2 are presented, and the destabilization of a monoclinic relative to a rhombohedral structure is discussed.
Sulfone Containing Clay Electrolytes and Their Potential for Li-Rechargeable Batteries
Authors: Moore Gregory J. , Whittingham M. Stanley
Published: April 2011

Clays have been synthesized and several types of molecules have been intercalated into them to enhance their ionic conductivity. The clay has the molecular formula of Litaeniolite, Li(Mg2Li)Si4O10F2, and the inserted molecules include PEO and two varieties of sulfone, tetramethylene sulfone and ethylmethyl sulfone. These have been made in the interest of electrolytes in lithium secondary batteries in order to produce a truly solid state cell. The products have been thoroughly characterized by x-ray diffraction to verify the uptake of the molecules into the layers, thermal analysis to observe the stabilization of the intercalated molecules, along with impedance measurements to test their conductivity.
Direct Observation of Xrd Redox Processes in TMO'S
Authors: Björk H. , Gustafsson T. , Thomas J.O.
Published: April 2011

Accurate XRD, often in combination with ND, has long been used to study electron density features in crystalline compounds. The method is particularly successful for light-atom systems in which the valence-to-core electron ratio is high. The same method is clearly applicable to the study of (typically) lithium insertion/extraction processes in TMO compounds; the greatest hinder has been the availability of sufficiently large single crystals, which do not then disintegrate into micron-size particles during the reaction. The case of V6O13 is especially advantageous in this context, however: millimeter-size crystals can be grown by CVT methods, which do not then exhibit severe cracking on lithium insertion, probably as a result of the layer-like nature of the structure. A sequence of single-crystal phases have now been studied in this way (LixV6O13 for x= 0, 1.0, 2.0 and 3.0) following in situ electrochemical synthesis in the composite cathode of a  half-cell. The resulting structures have been solved, and their associated electron-density distributions carefully analysed by so-called Hirshfeld deformation electron density refinement. The method would appear to provide meaningful information relating to oxidation state changes occurring on lithium-ion insertion.
Manganese Dioxides: Chemical-Structural Disorder, Electronic Properties, Electrochemical Activity and Proton Diffusivity
Authors: Poinsignon C.J.
Published: April 2011

Several synthetic and natural manganese dioxides (MD) are characterized in terms of chemical composition, structural disorder and electrochemical activity; semi conducting properties are examined on pressed powdered samples. The reactivity scale established between structural disorder and electrochemical reactivity is paralleled by semi conducting properties and proton diffusivity. Conductivity values of 0.15 S.cm−1for stoechiometric β-MnO2, 1.3 10−2, 2.5 10−2 and 3.7 10−2 S.cm−1 for the defect dioxides, respectively Synthetic-Ramsdellite, CMD and EMD are measured. Proton diffusivity study by EIS provides, for low reduction rate, diffusion coefficient D values varying from 10–15 cm2/s value to 10−16 for the best reactive forms EMD and CMD; for NMD and β-MD, D is respectively 10−16 and 10−21 cm2/s. Redox reversibility is obtained around 1.3V (vs Hg.HgO) for EMD for a one electron reduction in [KOH] <IM; at -0.4V for a 2 electrons reduction in 9M KOH for Bi modified NMD.
Reactivity of Carbonaceous Anodes Used in Lithium-ion Batteries, Part I: Correlation of Structural Parameters and Reactivity
Authors: Nazri G. A. , Yebka B. , Nazri M. , Curtis D. , Kinoshita K. , Derwin Dave
Published: April 2011

Carbonaceous anodes are the most practical elecrode for application in lithium-ion battery, mainly due to their low cost, flexibility for modification to achieve high energy capacity and high rate capability, abundance and environmentally uniquencess. Despite superior advantages of carbonaceous anodes vs other alternative anode and metallic lithium, there is considerable reactivity of lithiated graphite with organic electrolytes, which is a major safety concern. In this work, we report the nature of gaceous species generated on various carbonaceous anodes during initial charge-discharge cycling. The correlation between structural parameters of carbonaceous materials and their irreversible capacity loss have been investigated. Structural parameters have been studied using x-ray diffraction, Raman spectroscopy, and scanning and transmission electron microscopy. We have found a direct correlation between crystal morphology, degree of disorder, degree of graphitisation and the irreversible capacity loss. There is also a direct correlation between the irrversible capacity loss and the volume of gas generated during initial charge- disharge cycling. Results also show the importance of removing adsorbed and trapped gases in addition to removal of bonded impurities, such as functional groups from carbonaceous electrode before fabrication of batteries.

Particular attention is given on thermal analysis for different graphite compounds and the influence of different parameters and conditions: nature of graphite in term of specific surface area, degree of graphitization and the length of microcristallites, degree of intercalation, nature of electrolytes on irreversible capacity loss and volume of gases generated during the initial charge-discharge cycles.
Spectroscopic and Transport Properties of Lithium Salts in Ethylene Carbonate Based Mixed Solvents for Lithium Batteries
Authors: Nazri M. , Nazri G. A. , Aroca R.
Published: April 2011

Electrolyte solutions formed by the addition of lithium hexafluorophosphate (LiPF6) and lithium perchlorate (LiC104) to solvents obtained by mixing ethylene carbonate (EC) with propylene carbonate (PC) and dimethyl carbonate (DMC) were studied. The temperature dependence of conductivity, infrared and Raman spectra of the EC-DMC and PC-EC-DMC solvent electrolytes are discussed. The experimental and theoretical studies of characteristic vibrations of DMC are reported.
Use of Mössbauer Spectroscopy for the Characterization of Order/Disorder Phenomena in Tin(II) Containing Ionic Conductors and for Making Predictions Regarding Possible Electron Contribution to the Conduction
Authors: Dénès Georges , Madamba M. Cecilia , Muntasar Abdualhafeed , Peroutka Alena , Tam Korzior , Zhu Zhimeng
Published: April 2011

Mössbauer spectroscopy has been seldom used for the characterization of ionic conductors. However, since the introduction of divalent tin in MF2 fluorites (M = Sr, Pb and Ba) to form MSnF4, PbSn4F10 or the Pb1−xSnxF2 solid solution, all of which have structures closely related to the fluorite type, results in an enhancement of the fluoride ion conductivity by up to three orders of magnitude, and since 119 Sn is the second best Mössbauer nuclide, it seems that the Mössbauer technique could provide useful information about how tin(II) modifies the fluorite structure and leads to such a tremendous enhancement of the fluoride ion mobility. The MF2/SnF2 systems contain some number of materials that show order/disorder phenomena (between M and Sn, and also between different fluorine atoms) which make it difficult to understand them from diffraction data only. Mössbauer spectroscopy has been invaluable in helping understand the local structure at tin. By probing the valence electronic structure of tin, we can also make predictions on the possible long range mobility of the tin(II) non-bonded electron pair, which would make the material an electronic conductor or a mixed conductor.
Preparation and Electrical Conductivity of Bismuth-Doped Antimonic Acids
Authors: Ozawa K. , Sakka Y. , Amano M.
Published: April 2011

Bismuth-doped antimonic acids with the empirical formula Sb2O5·xBi2O3·nH2O (0 ≤ x ≤ 0.2) were prepared by reacting an H2O3, aqueous solution with Sb(O-i-C3H7)3and Bi(O-i-C3H7)3. X-ray diffraction confirmed that the anhydrous composites, Sb2O·xBi2O3(0 ≤ x ≤ 0. 1), are a single cubic Sb2O5phase, where the cubic cell parameter increases linearly from 10.277 to 10.380 Å with the bismuth content x. The electrical conductivity of the polycrystalline disks for Sb2O5·xBi2O3·nH2O (0 ≤ x ≤ 0.1) was evaluated by an ac impedance method at 19.5 °C under various conditions of relative humidity. The conductivity of Sb2O5·xBi2O3·nH2O with x = 0.1 was found to be high (1.0 × 10−3Scm−1) even at a relative humidity of 68.3%. There was a stronger humidity dependence than that of Sb2O5·xBi2O3·nH2O with x = 0.
Ionic Conductivities and Microstructures of CeO2:Y203 Solid Electrolytes
Authors: Tian Chunyan , Chan Siu-Wai
Published: April 2011

Ionic conductivities of solid CeO2:Y203 electrolytes were systematically investigated as a function of dopant concentration and sintering temperatures. The highest lattice conductivity occurred at 6–8% dopant concentration, and maximum grain boundary conductivity was observed at 10% dopant concentration. The sintering temperature was found to have a significant effect on the conductivities of the pellets. The samples sintered at lower temperatures (T≤140°C) showed higher grain boundary conductivity than those sintered at 150°C; this was found to be related to size-dependent-impurity segregation and precipitation at grain boundaries. The grain boundary conductivities as related to the microstructure are discussed by adopting different grain boundary models. Solute segregation and oxygen depletion at grain boundaries, which have been suggested to be responsible for the grain boundary resistivities in these samples, were examined by a microanalytical technique for small-grain-size samples.
Copper-Conducting Nasicon-Type CuTi2(PO4)3 Glass-Ceramics for Application to a Novel O2 Sensor
Authors: Yamamoto K. , Kasuga T. , NOGAMI M.
Published: April 2011

Fast Cu+-conducting ceramics containing NASICON-type CuTi2(PO4)3 and Cu3 (PO4)2 phases, which three-dimensionally interlock with each other, has been successfully prepared by the controlled crystallization of glass in the Cu-Ti-P-O system. The electrical conductivity of the glass-ceramic was ∼3×10−4Scm−1 at 300°C. The obtained glass-ceramics was applied to an oxygen-concentration cell operating at low temperature such as 100°C. The electromotive force (EMF) of the sensor showed good Nemstian response. The mechanism for O2 sensing is discussed in terms of the redox reaction between Cu+ ion in the dense glass-ceramic and O2 gas.
Trivalent Ion Conduction in the Scandium Tungstate-Type Structure
Authors: Imanaka N. , Kobayashi Y. , Tamura S. , Fujiwara K. , Asano T. , Okazaki Y. , Adachi G.
Published: April 2011

The realization of a trivalent ion conduction in solids was successful by selecting the Sc2(WO4)3-type structure from the consideration of the mobile trivalent cations and the structure which decreases the electrostatic interaction between the migrating trivalent ionic species and the framework structure as much as possible. Among the rare earth tungstates, Sc2(WO4)3 (σ600°C=6.5× 10−5 S'cm−1, Ea=44.1 kJ.mo−1) was found to hold the most suitable size for the trivalent ion migration in the relation between the mobile ion size and the lattice volume. The ion conducting characteristics of rare earths were studied by means of both the polarization and dc electrolysis techniques. The mobile species was demonstrated to be the trivalent ions in the Sc2(WO4)3-type structure. By the dc electrolysis, the mobile ion species was definitely identified to be the trivalent ions in the Sc2(WO4)3-type tungstates. In addition, the demonstration of a macroscopic Al3+ ion conduction in the tungstate structure was directly accomplished.
High Reflectivity Modulation Electrochromic Windows
Authors: Gerouki A. , Goldner R.B.
Published: April 2011

In this paper we report the fabrication of high reflectivity modulation electrochromic Windows (ECW's) which have exhibited a colored state reflectivity of more than 50% for the wavelength range of 1 to 2.5 µm with an average bleached state reflectivity of 20%. The transmissivity of these ECW's in the colored state was less than 5% and in the bleached state it averaged 60%. The materials employed were tungsten oxide (nominally WO3) for the first electrochromic electrode, lithium cobalt oxide (nominally LiCoO2) for the second, complementary, electrochromic electrode, lithium phosphorus oxynitride (Lipon) for the ionic conductor (electrolyte), and indium tin oxide (ITO) and indium oxide (In2O3) for the two transparent electronic conductors. The predicted and measured reflectivity of the ECW's were influenced by the first transparent conductor (TM) in relation to its thickness and optical properties. Devices without a TC1 exhibited the highest reflectivity modulation, It was also concluded that two of the main limitations to the degree of reflectivity modulation attainable with the ECW's were lithium insertion into TC1 and electronic transport through the electrolyte.
Light Emitting Electrochemical Cells as Mixed Ionic Electronic Conductors
Authors: Riess I. , Cahen D.
Published: April 2011

Polymer electrochemical cells have been reported to emit light. The current and light output increase rapidly with voltage, apparently beyond 2V. The polymer is an ionic conductor as well as an electronic (electron/hole) conductor, i.e. a mixed ionic-electronic conductor (MIEC).

The I-V relations are explained here to be those of an MIEC of a particular defect model placed between two ion blocking electrodes. This MIEC defect model assumes a large concentration of mobile ions and small concentrations of electrons and holes. A p and an n region are formed in the MIEC. However, there is no space charge within the MIEC and it stays neutral. The resulting I-V relations are exponential. A good fit to the experimental data is obtained when electrode over-potential and heating of the polymer under current are taken into consideration.
Pd, Pt and ZrO2-Pt Films Prepared by Mocvd and Their Electrochemical Properties
Authors: De Oca J.A. Montes , Vargas J.R. , Godinez J.
Published: April 2011

Pd, Pt and ZrO2-Pt films were prepared by metal organic chemical vapor deposition (MOCVD) as electrodes for zirconia solid electrolyte and their electrochemical properties were examined by impedance spectroscopy. Carbon containing films (Pt-C and Pd-C) consisted of agglomerated fine particles (2-5 nm in diameter) exhibit higher electrode conductivities than that of conventional Pt paste electrodes at temperatures below 873 K. The sintering of the fine particles and/or oxidation of impurity carbon or Pd spoil their electrochemical performance. On the other hand, two-phase ZrO2-Pt films show promise as electrode material for zirconia electrolyte at low temperatures (below 973 K) because of their higher conductivity than Pt paste electrodes and their thermal stability.
General Overview of Vibrational Spectroscopy of Layered Transition-Metal Oxides
Authors: Julien C. , Nazri G.A.
Published: April 2011

We report the vibrational spectra of various layered transition-metal oxides, which are potential cathode materials for advanced Li-ion batteries. They provide high specific energy density, high voltage, and remarkable reversibility for lithium intercalation-deintercalation process. Studies were carried out by Raman and FTIR spectroscopies. Oxides such as LiMO2 (M=Co, Ni, Cr) layered compounds and their mixed compounds have been investigated. The local environment of cations against oxygen neighboring atoms has been determined by considering polyhedral units building the lattice. Structural modifications induced by intercalation-deintercalation process, by cation substitution, or by low-temperature preparation route are examined.
Synthesis and Chemical Properties of Dye-Doped Mesoporous Transition Metal Oxides
Authors: Honma I. , Zhou H.S. , Moon S.C.
Published: April 2011

Self-assembled functional dye molecules in mesoporous transition metal oxides have been synthesized directly by Pc (phthalocyanine) molecules doped within hexadecyltrimethylammonium bromide (C16TMA) micelles assembled with oxide frameworks such as Vanadia (VOX), FeOx, MoO3and WO3to produce Pc-doped mesostructured materials. The Pc molecules were heavily doped inside the mesoporous channels and dye's optical absorption were measured. Pc molecules in contact with mesoporous transition metal oxides interfaces are optically excited and provide reductive electrons to water molecules to decompose into hydrogen by visible light exposures.
Platinum Supported Catalysts Prepared from Metal Carbonyl Clusters for Hydrocarbons Conversion
Authors: Kolosov P.E. , Shitova N.B. , Smolikov M.D. , Drozdov V.A. , Moroz E.M.
Published: April 2011

The investigation of surface Pt/alumina, Pt/ carbon (Sibunit) and Pt/SiO2 species prepared by anchoring of Pt carbonyl clusters of various nuclearity as precursors for high dispersive and thermostable platinum supported catalysts for hydrocarbons conversion, using RDF (radial distribution functions) and chemisorption methods, has shown strong metal-support interaction with formation of Pt/alumina phase with highly dispersed (practically monoatomic) and homogeneously distributed Pt atoms onto alumina surface. The catalytic properties were studied in methane oxidation and cyclohexane dehydrogenation reactions.
Heteropoly Acids Supported on Sol-Gel Matrices and Their Catalytic Activity and Selectivity
Authors: Grandstaff D.E. , Paciolla M. D. , Sein L.T. , Jacob R. , Narielwala K. , John S. , Patel N. , Kashani M. , Doll K. , Wei Y. , Jansen S. A.
Published: April 2011

Heteropoly acids (HPA) are well known solid acids as well as oxidation catalysts. They find application in both homogeneous and heterogeneous reactions. As catalysts, problems associated with surface area and instability are diminished by supporting the HPA. It has been reported that supporting these materials on oxide substrates or porous carbon materials has resulted in some degree of instability. It has also been shown that encapsulating HPA in sol-gel silica matrices has produced an increase in catalytic performance without compromising the catalytic activity of the HPA. In this work, we analyzed the activity of a silica sol-gel supported HPA catalyst. The reaction which was chosen to illustrate such issues was the oxidation/dehydration of 1-butanol. In addition, the specific role of the support in the catalytic process is described. In this work, we characterized the silica-sol gel supported HPA catalyst to try to understand the effect of preparation in the overall catalytic selectivity and activity.
Potential of Monolithic Reactors in Catalysis; Multiphase Applications
Authors: Moulijn Jacob A. , Kapteijn Freek
Published: April 2011

Several aspects of the application of monolithic catalysts in multiphase reactions are highlighted: why, hydrodynamics and preparation. A bright future for monolithic systems in this area is predicted for application in chemical industry.
Activation of Alkanes by Transition Metal Nitrides and Carbides
Authors: Bennett C. A. , Neylon M. K. , Kwon H. H. , Choi S. , Curry K. E. , Thompson L. T.
Published: April 2011

Group V and VI nitrides and carbides were synthesized by the temperature programmed reaction of metal oxides with ammonia or an equimolar mixture of methane/hydrogen. The synthesis protocols were developed using thermogravimetric techniques. The resulting nitrides and carbides were primarily mesoporous and possessed surface areas in the range of 11 – 81 m2/g. Their alkane activation rates were comparable to a Pt-Sn/AL20 3 dehydrogenation catalyst and the surface area normalized reaction rates decreased in the following order: Mo2N > W2C > WC > W2N > WC1−x > VCoa0.05N > MO2C > VN = VC > NbMo0.01 N > NbMo0.05 > NbN = NbC. The activities measured at 450°C ranged between 1011 – 1013 molecules/cm2/s for n-butane and 1012 – 1013 molecules/cm2/s for n-hexane. The Group VI nitrides and carbides were far more active than the Group V materials. The Group VI materials catalyzed the hydrogenolysis and dehydrogenation reactions with similar activities whereas the Group V materials were more than 98% selective to dehydrogenation. While the metal atom type had the most significant effect on the catalytic properties, the lattice structure of the material also played a role. In particular, we observed that WC (hex) was almost twice as active as WC1-x (fcc). Nitrides and carbides of the same metal and lattice structure possessed similar catalytic properties, implying that the effect of the non-metal atom type was minimal. The W2N catalyst was found to be highly selective towards n-butane isomerization. The multimetallic nitrides each demonstrated some form of synergy.
Synthesis Of Highly Ordered Macroporous Minerals: Extension of the Synthetic Method to Other Metal Oxides and Organic-Inorganic Composites
Authors: Blanford C.F. , Do T.N. , Holland B.T. , Stein A.
Published: April 2011

The facile synthesis of three-dimensional macroporous arrays of titania, zirconia and alumina was recently reported [1]. The synthesis of these materials has now been extended to the oxides of iron, tungsten, and antimony, as well as a mixed yttrium-zirconium system and organically modi- fied silicates. These materials were characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray energy dispersive spectrometry (EDS), and powder X-ray diffraction (XRD). Ordered structures of iron, tungsten, and antimony were formed from alkoxide precursors as in the originally reported synthesis, but the template was removed at a lower temperature. Samples of vinyl- and 2-cyanoethyl-modified silicates were formed from a mixture of organotrialkoxysilane and tetraalkoxysilane precursors; the polystyrene template was removed by extraction with a THF/acetone mixture. These results show the ease of extending the original syn- thesis to a wide range of systems. Also, the ability to form homogenous mixed-metal oxides will be important for tailoring the dielectric and photonic properties of these materials.