bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Silicon Dopant and Processing on Thermoelectric Properties of B4C Ceramics
Authors: Cai Ke-Feng , Nan Ce-Wen , Min Xin-Min
Published: April 2011

B4C ceramics doped with various content of Si (0 to 2.03 at%) are prepared via hot pressing. The composition and microstructure of the ceramics are characterized by means of XRD and EPMA. Their electrical conductivity and Seebeck coefficient of the samples are measured from room temperature up to 1500K. The electrical conductivity increases with temperature, and more rapidly after 1300K; the Seebeck coefficient of the ceramics also increases with temperature and rises to a value of about 320μVK−1. The value of the figure of merit of Si-doped B4C rises to about 4 × 10−4K−1 at 1500K.
Thermoelectric Properties of Doped Rhenium Chalcogenides Re6MxTe15 (x = 0, 1, 2; M = Ga, In, Ag)
Authors: Dalafave S. Kilibarda , Barcena H. , Henningsen D.
Published: April 2011

Temperature dependencies of the electrical resistivity, ρ, and the thermoelectric power, α, are reported for Re6 MxTe15 (M = Ga, In, Ag; x = 0, 1, 2) between 90–380 K. Theoretical discussion of the results is presented. The materials, synthesized by filling large voids in the Re6Te15 cluster system, may have potential thermoelectric applications around and below room temperatures. The samples are prepared by reacting 99.99% pure elemental powders in evacuated and sealed quartz ampoules at 1070 K for 170 hours. The resistivity data indicate semiconducting behavior for all samples. Possible hopping conduction is present at lower temperatures. The energy gap is observed at higher temperatures in all the samples.

Positive values of α in Re6(Ga,In)x Te15 (x = 0, 1, 2) indicate p-type semiconducting behavior in the studied temperature range. For these samples α increases initially with temperature, then levels off to a nearly constant value. The positions of the sharp peaks in a, observed at lower temperatures for x = 1, 2 only, depend on the Ga (In) concentration. High values of a (∼ 300 μV/K) are measured at room temperatures. In Re6AgTe15 α has small positive values (∼ 20–40 μV/K) between 185 K and 270 K. Outside this range α is negative. It reaches local maxima of -340 μV/K at 105 K and -350 μV/K at 370 K. In Re6Ag2Te15 α changes from positive to negative values above 295 K. A maximum positive value of +350 μV/K is reached at 250 K and maximum negative of -250 μV/K at 330 K. The power factor, α2/ρ, increases with temperature for all studied samples. Theoretical fits to α(T) for all samples are discussed. Also discussed is the effect of filling the voids in the rhenium-telluride system on the figure of merit.
Prospects for Bismuth Nanowires as Thermoelectrics
Authors: Dresselhausa M. S. , Zhang Z. , Sun X. , Ying J. Y. , Heremans J. , Dresselhaus G. , Chen G.
Published: April 2011

The small effective mass of Bi, high anisotropy of its Fermi surface, and the high aspect ratio (length/diameter) of Bi nanowires make this an excellent system for studying quantum confinement effects of a one-dimensional (ID) electron gas in relation to electrical conductivity, thermoelectric power, and thermal conductivity. A theoretical model based on the basic electronic band structure of bulk Bi is suitably modified to describe 1D bismuth nanowires and is used to predict the dependence of these transport properties on nanowire diameter, temperature and crystalline orientation of the bismuth nanowires. Experiments have been carried out on ultra-fine single crystal Bi nanowires (10–120 nm diameter) with a packing density as high as 7 × 1010 wires/cm2 to test the quantum confinement assumptions of the model and the occurrence of a quantum confinement-induced semimetal-to-semiconductor transition as the wire diameter becomes less than 100 nm. Prospects for the use of bismuth nanowires for thermoelectric applications are discussed.
Pressure-Tuning in the Search for Improved Thermoelectric Materials
Authors: Polvani D. A. , Meng J. F. , Jones C. D. W. , DiSalvo F. J. , Badding J. V.
Published: April 2011

The traditional approach to the search for improved materials, such as thermoelectric materials, involves the sequential synthesis and characterization of new compounds, followed by the investigation of their properties. Each single solid state compound has materials interaction parameters (e.g., degree of orbital overlap, orbital energy, band energies etc.) that determine its thermoelectric properties. These interaction parameters can be used to define a phase space, in which individual compounds are represented by a single point. Because this phase space can be rapidly explored with pressure, our efforts have focused on the synthesis of complex semiconductors and rare earth based materials, followed by pressure-tuning studies of their thermoelectric properties. This approach to exploring interaction parameter phase space potentially allows the thermoelectric power to be more rapidly and cleanly optimized than is possible with the traditional approach. Here we present some results for rare earth thermoelectric compounds that have been pressure-tuned. Demonstration of the existence of materials with improved ZT at high pressure can also provide insight into the structural and electronic parameters necessary to achieve high figures of merit at ambient pressure.
Properties of Novel Thermoelectrics from First Principles Calculations
Authors: Singh D. J. , Mazin I. I. , Feldman J. L. , Fornari M.
Published: April 2011

The use of first principles methods based on density functional theory to investigate novel thermoelectric materials is illustrated for several empty and filled skutterudite compounds, including CoSb3, COP3, La(Fe,Co)4Sb12 and La(Fe,Co)P12. Band structures and their relationship to transport properties especially as regards optimization of thermoelectric properties is discussed. Phonon models constructed from calculations and existing experimental data for CoSb3 are presented. These have been extended to the filled skutterudites, particularly LaFe4Sb12 using additional first principles calculations to fix the La related parameters in the model. This model allows an interpretation of neutron scattering data as well as an understanding of the low frequency phonon modes that transport heat in these compounds.
Thermoelectric Properties of Single-Wall Carbon Nanotubes
Authors: Grigorian L. , Sumanasekera G. , Eklund P. C
Published: April 2011

Results of the temperature dependence of the thermoelectric power and fourprobe resistance of single wall carbon nanotube mats are presented. The data are interpreted in terms of the response of a percolating network of metallic nanotube bundles. To the best of our knowledge, the work represents the first systematic study of the transport properties of a series of samples prepared using different transition metal-Y growth catalysts. Although x-ray diffraction and Raman scattering data indicate these samples are nominally the same, we find that the identity of the catalyst has a pronounced effect on the electrical transport properties. The data are interpreted qualitatively in terms of a dilute Kondo system involving the coupling of the the localized magnetic moments of impurity atoms (derived from the catalyst), and the conduction electron spins in the nanotube walls.
Nickel Substituted Skutterudites: Synthesis and Physical Properties
Authors: Chapon L. , Ravot D. , Tedenac J. C.
Published: April 2011

Starting to CeFe4Sb12 and trying to obtain low gap semiconductors with very low thermal conductivity, we have performed in this compound the substitution of Ni for Fe.This substitution induces a reject of cerium from the structure. In this paper we present synthesis and physical properties of CeyFe4-xNixSb12 in which a relationship is existing between x and y to retain the electronic account giving semiconducting character.
Imaging of the Carrier Density of States in Low Dimensional Structures Using Electrostatic Force Microscopy
Authors: Gekhtman D. , Zhang Z. B. , Adderton D. , Dresselhaus M. S. , Dresselhaus G.
Published: April 2011

In this work we show that scanning probe electrostatic force microscopy (EFM) can be applied to low dimensional electronic nanostructures for imaging the density of states of quantum confined carriers. The results on EFM studies are presented for quasione- dimensional (ID) Bi quantum wire arrays and quasi-two-dimensional (2D) GaAs/AlxGa1-x As multiple quantum well structures.
Thermal Conductivity and Phonon Engineering in Low-Dimensional Structures
Authors: Chen G. , Volz S. G. , Borca-Tasciuc T. , Zeng T. , Song D. , Wang K. L. , Dresselhaus M. S.
Published: April 2011

Understanding phonon heat conduction mechanisms in low-dimensional structures is of critical importance for low-dimensional thermoelectricity. In this paper, we discuss heat conduction mechanisms in two-dimensional (2D) and one-dimensional (1D) structures. Models based on both the phonon wave picture and particle picture are developed for heat conduction in 2D superlattices. The phonon wave model, based on the acoustic wave equations, includes the effects of phonon interference and tunneling, while the particle model, based on the Boltzmann transport equation, treats the internal as well interface scattering of phonons. For 1D systems, both the Boltzmann transport equation and molecular dynamics simulation approaches are employed. Comparing the modeling results with experimental data suggest that the interface scattering of phonons plays a crucial role in the thermal conductivity of low-dimensional structures. We also discuss the minimum thermal conductivity of low-dimensional structures based on a generalized thermal conductivity integral, and suggest that the minimum thermal conductivities of low-dimensional systems may differ from those of their corresponding bulk materials. The discussion leads to alternative ways to reduce thermal conductivity based on the propagating phonon modes.
Carrier Pocket Engineering to Design Superior Thermoelectric Materials Using GaAs/AlAs Superlattices
Authors: Koga T. , Sun X. , Cronin S. B. , Dresselhaus M. S.
Published: April 2011

A large enhancement in the thermoelectric figure of merit for the whole superlattice, Z3DT, is predicted for short period GaAs/AlAs superlattices relative to bulk GaAs. Various superlattice parameters (superlattice growth direction, superlattice period and layer thicknesses) are explored to optimize Z3DT, including quantum wells formed at various high symmetry points in the Brillouin zone. The highest room temperature Z3DT obtained in the present calculation is 0.41 at the optimum carrier concentration for either (001) or (111) oriented GaAs(20 Å)/AIAs(20 Å) superlattices, which is about 50 times greater than the corresponding ZT for bulk GaAs obtained using the same basic model.
Thermoelectric Properties of the AIPdMn Quasicrystalline System
Authors: Pope A. L. , Tritt T. M. , Chernikov M. , feuerbacher M. , Legault S. , Gagnon R. , Strom-Olsen J.
Published: April 2011

We have begun a systematic investigation the electrical transport properties of the AlPdMn quasicrystalline system. Resistivity and thermopower measurements have been performed over a temperature range between 5K and 320K. In the pure, single phase Al70Pd20Mn10 we have observed thermopowers as high as +80 μV/K around room temperature with resistivities of 1.5 mΩ-cm. Thermal conductivity measurements have been performed yielding values less than 2 W/m-K for all the samples investigated to date. We will discuss how the thermopower and resistivity vary as a result of differing sample composition as well as different processing and annealing conditions. Several different preparation techniques have been employed to further understand how various factors affect the thermal and electrical properties of this quasicrystalline system and how these may be adjusted to optimize these materials for possible thermoelectric applications.
Hot Electron Effects on Thermionic Emission Cooling in Heterostructures
Authors: Zeng Taofang , Chen Gang
Published: April 2011

The energy conversion between electrons and phonons in a heterostructure is studied for thermionic cooling by using the hot electron approximation. Calculations show that the energy exchange rate between electrons and phonons should be small for a net cooling power, and the layer length should be in the range of submicron for effective cooling.
Anisotropic Thermal Conductivity of A Si/Ge Superlattice
Authors: Borca-Tasciuc T. , Song D. , Liu J. L. , Chen G. , Wang K. L. , Sun X. , Dresselhaus M. S. , Radetic T. , Gronsky R.
Published: April 2011

Experimental evidence for a significant thermal conductivity reduction have been reported in recent years for GaAs/AlAs, Si/Ge, and Bi 2Te3/Sb2Te3 superlattices. In this work, we present preliminary experimental results on the reduction of the in-plane and cross-plane thermal conductivity for a symmetric Si/Ge superlattice. A differential 2-wire 3ω method is developed to perform the anisotropic thermal conductivity measurements. In this technique, a patterned heater with a width much larger than the film thickness yields the cross-plane thermal conductivity of the film. The in-plane thin film thermal conductivity is inferred from the temperature rise of a narrow width heater that can create more heat spreading in the in-plane direction of the thin film. A differential method to measure the temperature drop across the film is employed in order to increase the accuracy of the measurement.
Development of Thick-Film Thermoelectric Microcoolers Using Electrochemical Deposition
Authors: Fleurial J.-P. , Borshchevsky A. , Ryan M. A. , Phillips W. M. , Snyder J. G. , Caillat T. , Kolawa E. A. , Herman J. A. , Mueller P. , Nicolet M.
Published: April 2011

Advanced thermoelectric microdevices integrated into thermal management packages and low power, electrical source systems are of interest for a variety of space and terrestrial applications. By shrinking the size of the thermoelements, or legs, of these devices, it becomes possible to handle much higher heat fluxes, as well as operate at much lower currents and higher voltages that are more compatible with electronic components. The miniaturization of state-of-the-art thermoelectric module technology based on Bi2Te3 alloys is limited due to mechanical and manufacturing constraints for both leg dimensions (100–200 μm thick minimum) and the number of legs (100–200 legs maximum). We are investigating the development of novel microdevices combining high thermal conductivity substrate materials such as diamond, thin film metallization and patterning technology, and electrochemical deposition of thick thermoelectric films. It is anticipated that thermoelectric microcoolers with thousands of thermocouples and capable of pumping more than 200 W/cm2 over a 30 to 60 K temperature diffrence can be fabricated. In this paper, we report on our progress in developing an electrochemical deposition process for obtaining 10–50 μm thick films of Bi2Te3 and its solid solutions. Results presented here indicate that good quality n-type Bi2Te3, n-type Bi2Te2.95Se0.05 and p-type Bi0.5Sb1.5Te3 thick films can be deposited by this technique. Some details about the fabrication of the miniature thermoelements are also described.
Synthesis of New Thermoelectric Materials Using Modulated Elementary Reactants
Authors: Sellinschegg Heike , Williams Joshua R. , Maxwell Steven P. , Sillars Douglas , Johnson David C.
Published: April 2011

Modulated elemental reactants have been used to synthesize metastable ternary compounds with the skutterudite crystal structure. The initial reactants are made up of multiple repeats of a unit containing elemental layers of a ternary metal, iron or cobalt (or a combination of these two) and antimony. The elemental layers interdiffuse upon low temperature annealing and form amorphous reaction intermediates. In this paper we target the compounds PbxFe4−yCoySb12. On annealing at temperatures between 12° and 150° C (depending on the composition) crystallization of the skutterudite structure occurs. The compounds are only kinetically stable, decomposing into a mixture of binary compounds upon annealing past a temperature of about 600°C. Preliminary data for the Seebeck coefficient and the electrical conductivity was collected The thermoelectric properties of the lead cobalt antimony skutterudite - films were measured as a function of lead occupancy.
Chevrel Phases as Good Thermoelectric Materials
Authors: Roche C. , Pecheur P. , Riffel M. , Jenny A. , Scherrer H. , Scherrer S.
Published: April 2011

Chevrel phases have an open lattice with large voids in which cations can be inserted. These cations are good scattering centers for phonons. The thermal conductivity of these compounds must be low. Chevrel phases are generally metallic, but we calculated the density of states of several compounds and we found that Zn2Mo6Se8, Cd2Mo6Se8, TiMo6Se8 are semiconducting whereas SnMo6Se8, Cu2Mo6Se8 and CrMo6Se8 are metallic. We are currently trying to synthesize Zn2Mo6Se8 by different ways.
Extraction of the Coefficient of Thermal Expansion of Thin Films from Buckled Membranes
Authors: Ziebartl V. , Paul O. , Baltes H.
Published: April 2011

We report a new method to measure the temperature-dependent coefficient of thermal expansion α(T) of thin films. The method exploits the temperature dependent buckling of clamped square plates. This buckling was investigated numerically using an energy minimization method and finite element simulations. Both approaches show excellent agreement even far away from simple critical buckling. The numerical results were used to extract Cα(T) = α0+α1(T−T0 ) of PECVD silicon nitride between 20° and 140°C with α0 = (1.803±0.006)×10−6°C−1, α1 = (7.5±0.5)×10−9 °C−2, and T0 = 25°C.
Reliability and Properties of Pzt Thin Films for Mems Applications
Authors: Bahr D. F. , Merlino J. C. , Banerjee P. , Yip C. M. , Bandyopadhyay A.
Published: April 2011

Thin films of PZT have been deposited using a solution deposition method onto platinized silicon substrates. The effects of process variables, including sintering time and solution molarity, have been investigated on the resulting microstructure and electrical properties. As utilizing piezoelectric thin films in geometries for MEMS applications requires load to be transferred between the film and an underlying membrane, the adhesion of these films has been examined using nanoindentation techniques. Delaminations occur at the PZT-Pt interface, suggesting that these films may be susceptible to interfacial failure with repeated bending. Longer firing times are shown to improve the adhesion of the films, but increase the surface roughness and grain size. Film hardnesses range between 4 and 6.8 GPa; for sintering times beyond 5 minutes at 700 °C the hardness appears relatively constant. Electrical properties are shown to degrade with tine at elevated temperatures.
Fullerene Derivatives as Novel Resist Materials for Fabrication of MEMS Devices by Electron Beam Lithography
Authors: Robinson A.P.G. , Palmer R.E. , Tada T. , Kanayama T. , Shelley E.J. , Preece J. A.
Published: April 2011

The fabrication of MEMS and electronic devices relies heavily on lithography. We have explored the application of derivatives of C60, as high resolution, high etch durability resists. Spin coating was used to produce films of various methanofullerenes on silicon substrates, with thickness ranging from 20 to 200 nm. These films behave as effective high resolution negative tone electron beam resists allowing sub 20 nm patterning of silicon which compares favorably with other negative tone resists. Organic solvents such as monochlorobenzene and chloroform can be used to develop the exposed films. The films have sensitivities of 4 × 10−3 to 8 × 10−4 C/cm2 for 20 keV electrons, more than an order of magnitude higher than the sensitivity of C60,. The dry etch durabilities of these compounds are considerably higher than those of conventional resists. A silicon grid with hole depth 160 nm and wall thickness 20 nm has been fabricated to demonstrate the high resolution and high etch durability of these resists.
The synthesis of novel polynuclear organogold complexes
Authors: Thomson J. , Fzea A. H. , Lobban J. , McGivern P. G. , Cairns J. A. , Fitzgerald A. G. , Berry G. J. , Davidson M. R. , Fan Y. C.
Published: April 2011

The synthesis and peirastic characterisation of two new organogold(III) complexes with a high molar ratio of gold content is described. The proposed formulae for the complexes in the present study are [C2H2Au4F8(PPh3)4]n and [C2H2Au4F8(NCCH3)4]n (Figure 1). These complexes were found to be stable to the atmosphere. The aim of this work was to demonstrate that such materials have a high metal to ligand ratio, suitable for physical vapour deposition process (PVD) and, hence, can be used as precursors for the deposition of pure metallic features. Physical and chemical characterisation methods were employed to obtain information about i) the structures, ii) the thermal and chemical stability, iii) the volatility and iv) the adhesion of these materials to specific substrates. These include n.m.r. (1H, 19F, 13C and 31P) IR spectroscopy, EDX (Energy Dispersive X-ray analysis), DSC ( Differential Scanning Calorimetry), TGA (Thermogravimetric Analysis), Powder X-ray Diffraction and Electron Microscopy (Scanning, Transmission and Atomic Force).
New Perovskite Oxide (Tl1/2Na1/2)TiO3
Authors: Shan Yue Jin , Nakamura Tetsuro , Miyata Mayuko , Kobashi Kazuhisa , Inaguma Yoshiyuki , Itoh Mitsuru
Published: April 2011

New perovskite-type oxide (Tl1/2Na1/2)TiO3 was synthesized by a cubic-anvil-type high pressure apparatus at 5.5 GPa and 1273 K for 30 sec. The perovskite-phase was found to have a tetragonal symmetry with space group P4/mmm. The lattice parameters a and c are 0.3811 nm and 0.3826 nm, respectively. An insulating skin covered the sample, but real resistivity is smaller and shows a metallic behavior.
Suppression of Exaggerated Grain Growth During Sintering of Nano-Sized Barium Titanate Powders
Authors: Meyers K.S. , Speyer R.F.
Published: April 2011

Rate controlled sintering (RCS) was used to sinter nano-sized BaTiO3 particles. A distinct shift in temperature slope above 1150-1200°C during RCS implied a change in sintering mechanism, and a corresponding exaggerated grain growth (grain size ~40-50 μm). By suppression of the exaggerated grain growth by firing a specimen packed in BaCO3, these phenomena were shown to be the result of a shift in phase equilibria from the volatilization of BaO from BaTiO3; the eutectic liquid which formed permitted rapid grain growth by a dissolution and precipitation process.
Effect of MnO on the Electrical Properties of Nb-Doped SrTiO3 Varistor
Authors: Kim S.-H. , Seon H.-W. , Kim Yoonho
Published: April 2011

The effect of MnO on the electrical properties of Nb-doped SrTiO3 was investigated to understand the electronic states of grains and grain boundaries. Grain size and dielectric constant were decreased with increasing Mn-doped content from 0 to 0.07 mol%. However, it was observed that the non-linearity coefficient of Nb-doped SrTiO3 was changed from 5 to 43 with Mn-doped content increasing from 0 to 0.03 mol%. Current-voltage (I-V) characteristics, capacitance-voltage (C-V) measurement, complex plane analysis and impedance spectroscopy were performed to obtain the information about the electrical properties of grains and grain boundaries. The potential barrier height increased and the donor concentration decreased with increasing Mn-doped content. This phenomena, that the electrical properties of Nb-doped SrTiO3 were changed with the addition of Mn, would be determined by the effect which Mn-2-3 substituted for Ti sites. It was observed that the breakdown voltage of single grain boundary was changed from 3.8 V to 8.9 V when measured by micro-electrode method.
Crystal Chemistry of New Calcium Tantalate Dielectric Materials
Authors: Grey Ian E. , Roth Robert S. , Mumme Gus , Bendersky Leonid A. , Minor Dennis
Published: April 2011

Doping of calcium tantalate, Ca2Ta2O7, with small amounts (<5 mole%) of Ca2Nb2O7 results in a 50% increase in the dielectric constant, K (from 23 to 35 at 1 MHz), and a zero temperature coefficient of K is achieved at about 18 mole% of Ca2Nb2O7. This opens up the possibility of applications in microwave communication devices. Crystallographic information needed to understand the structure/property relationships in this system is lacking. We have prepared samples of calcium tantalates doped with different elements including Nb, Sm, Ti, Nd and Zr, and have structurally characterised them using X-ray diffraction and transmission electron microscopy. The diffraction patterns of the tantalates all display strong subcell reflections characteristic of the trigonal weberite structure together with complex distributions of superlattice reflections that depend on the nature and concentration of the dopant and on the reaction temperature. The diffraction patterns were indexed using related trigonal or pseudo-trigonal unit cells with a ~7.3 Å, c ~ n × 6 Å. Polytypes with n = 3, 4, 5, 6 and 7 were prepared as single crystals by the flux method. Single crystal X-ray data was used in conjunction with high resolution electron microscope images to solve the structures. Details are given for a 6M polytype (M=monoclinic). A characteristic structural feature of the polytypes is a fluorite-type cation array which is periodically twinned on (111)f to give mixed cubic-hexagonal stacking of the cation layers. The structure relations with the pyrochlore and weberite structures are discussed.
Synthesis and Characterization of New Composite Oxides Related to the 2H-Perovskite Structure Type
Authors: Claridge J. B. , zur Loye H.-C.
Published: April 2011

The synthesis, structural characterization, and magnetic properties of three strontium rhodium oxides Sr6Rh5O15, Sr4Rh3O9+δ, and Sr9Rh7O21+δ, is presented. While Sr6Rh5O15 is an example of a commensurate n = 1 member of the A3n+3A'nBn+3O6n+9 family of oxides, Sr4Rh3O9+δ, and Sr9Rh7O21+°, are examples of incommensurate n =2 and n = 3 members. Sr6Rh5O15 crystallizes in space group R32, a = 19.3197(2) Å, c = 13.0418(1) Å. The Sr6Rh5O15 structure is a superstructure of the Ba6Ni5O15 structure type. Sr4Rh3O9+δ, and Sr9Rh7P21+δ crystallize in the superspace group with lattice parameters of a = 9.6007(6), c1 = 2.6881(2), c2 = 4.2373(3), and a = 9.6127(6), c1 = 2.6769(2), c2 = 4.252(1), respectively. Their magnetic data are consistent with antiferromagnetic coupling between the chains leading to an ordered state at low temperature.
A Coupled Compressible and Polarizable Ionic Model Applied to Oxide Crystal Structures
Authors: Marks N. A. , Fabris S. , Finnis M. W.
Published: April 2011

Compressible and polarizable ion models parametrized by ab initio calculations represent a promising technique for simulating challenging materials such as oxides. We present a new form of such a model in which the compression and polarization effects are coupled, and the anion-anion interaction is not fixed but dependent on the ion size and polarization. These two effects provide a more physically realistic description of a system, and significantly improve the predictive power of the method. Calculations on magnesium oxide show the elastic constants and other properties to be in good agreement with experiment. The new functional form is part of an ongoing project to develop an empirical model of zirconia, an important oxide for which a satisfactory model has yet to be determined.
A New Allotropic Form of Bi2O3
Authors: Kumada N. , Kinomura N.
Published: April 2011

Single crystals of a new allotropic form of bismuth sesquioxide, Bi2O3 were prepared by low temperature hydrothermal reaction using hydrated sodium bismuth oxide, NaBiO3·nH2O, as a starting material. This bismuth oxide crystallized in the orthorhombic space group Pccn with a=12.732(2), b=4.955(2) and c=5.582(2)Å, z=4, and the R-factors were R=0.030 and Rw=0.030 for 1702 unique reflections. The crystal structure is built up by corner- and edge-sharing of irregular BiO5 polyhedra and the tunnel is running along the c-axis.
Effect of Potassium Carbonate Additive on CO2 Absorption in Lithium Zirconate Powder
Authors: Ohashi T. , Nakagawa K.
Published: April 2011

Lithium zirconate, which reacts with CO2 reversibly at temperatures over 500°C, is expected to find wider application than conventional CO2 absorbents, as the latter can be used only at room temperature. We examined the effect of potassium carbonate, which had usually been added to facilitate the formation of lithium zirconate in the past, on the kinetics of CO2 absorption reaction. The result shows that the CO2 absorption rate of lithium zirconate powder is extremely accelerated by the potassium carbonate additive. We conclude that this acceleration results from the formation of a eutectic carbonate composed of Li2CO3 and K2CO3.
Synthesis of Epitaxial Thin-Films of Tetragonal Perovskites Via a Solution Technique
Authors: Beach David B. , Morrell Jonathan S. , Xue Ziling B. , Specht Eliot D.
Published: April 2011

Solution chemistry has been used to synthesize epitaxial films of SrLaGaO4, SrPrGaO4, SrLaAlO4, and SrPrAlO4 on single crystal substrates of [100] SrTiO3 and [100] LaAlO3. Precursor solutions were prepared from metal methoxyethoxides in 2-methoxyethanol. Films were prepared by spin-casting from partially hydrolyzed solutions followed by firing for 20 minutes in air at 850°C. The structure of the films was determined using X-ray diffraction. Theta/2-theta scans and omega scans (rocking curves) indicated that the films were c-axis aligned. Phi scans proved that the films were also aligned in-plane.
Preparation of YSZ Thin Film on Porous Electrode of SOFC
Authors: Nagamoto H. , Ikewaki H.
Published: April 2011

Porous electrode substrate of La0.7Sr0.2MnO3 was used as the support for the deposition of YSZ thin films. The porosity of the electrode substrate was controlled by sintering temperature and particle size of powders. Thin films of YSZ were fabricated on the electrode by sol-gel method. The YSZ film fabricated by 10-fold coating with 0.05M YSZ sol containing TEA was continuous and crack-free one of 5 mm in thickness. However, hydrogen permeation measurement showed that there was a very small leakage of hydrogen in the fabricated film. In addition to sol-gel method, another technique such as EVD should be employed to make the film completely gas-tight.
Factors Influencing the Electrochromic Properties of Nickel Oxide Thin Films Derived from Sol-Gel Method by Dip Coating
Authors: Sharma Pramod K. , Mracia M.C.A. , Fischer H. , Craievich A. F. , Gorenstein A.
Published: April 2011

The synthesis of thin film of nickel oxide is important due to their potential application in eletrochromic displays which can be used in optical displays and as windows controlling the light intensity. Dip coating through sol-gel method is a possible low energy method of coating. Hence this method of film growth has been chosen under various concentration of water, catalyst (acetic acid) and precursor. The films were characterized by XRD, FTIR, thickness profiler and SEM. The films which were synthesized with the concentration of Ni=0.005 molar were found to have low positive current density while the coloration was getting dark when concentration of Ni was increased to 0.015 molar. Increase in concentration of acetic acid decreases the positive current density. Small-Angle X-ray Scattering (SAXS) and density measurements were carried out for the structural characterization of the xerogels. A denser material was obtained at high concentration of acetic acid. The physical and chemical properties of the films and xerogels are well correlated with the electrochemical properties of the films.
Solid-State Heteronuclear-Correlation NMR Studies of Multicomponent Phosphate Glasses
Authors: Prabakar S. , Egan J.M. , Wenslow R.M. , Mueller K.T.
Published: April 2011

The correlation between 23Na and 31P nuclei in alkali phosphates has been investigated by cross-polarization MAS NMR spectroscopy. Connectivity between sodium ions with various phosphorus tetrahedra has been demonstrated in a variety of crystalline-and amorphous alkali phosphates. CPMAS NMR experiments were also performed on sodium aluminophosphate glasses from both quadrupolar nuclei (23Na and 27Al) to the phosphorus nuclei to establish connectivity of sodium and phosphorus as well as aluminum and phosphorus nuclei in these systems.
Variable Dimensionality in The Uranium Fluoride / 2-Methyl-Piperazine System: Syntheses and Structures of UFO-5, 6, and 7; Zero, One, and Two Dimensional Materials with Unprecedented Topologies
Authors: Halasyamani P.S. , Francis R.J. , Bee J.S. , O'Hare D.
Published: April 2011

The hydrothermal syntheses and structures of a new series of organically templated UIV materials are presented. The materials, UFO-5 (C5NH14)2(H3O)U2F13, UFO-6 (C5N2H14)2U2F12H2O and UFO-7 (C5N2H14)(H3O)U2F11, exhibit unprecedented topologies as well as represent 0-D (UFO-5), 1-D (UFO-6), and 2-D (UFO-7) phases. By systematic experimentation and utilizing a composition prism, wherein the reagents including H20 are graphically depicted. we have determined stability regions in which UFO-5, 6, and 7 can be synthesized as phase pure products. In addition, through pH measurements we observe a direct relationship between the acidity of the reaction and the dimensionality of the product. We suggest that the increased acidity facilitates condensation of the molecular uranium units in UFO-5. to produce the 1-D UFO-6 and at higher acidity the 2-D UFO-7.
Commensurate and Incommensurate Oxide Structures Related to 2H Perovskite
Authors: Battle P. D. , Blake G.R. , Burley J.C. , Cussen E. J. , Sloan J. , Vente J. F. , Darriet J. , Weill F.
Published: April 2011

The magnetic structures of Ca3LiRuO6 and Ca3NaRuO6 have been deduced from powder neutron diffraction data. In each case successive Ru5+ cations in the [001] chains of the Sr4PtO6-like structure are antiferromagnetically coupled, and nearest-neighbour Ru5+ cations in adjacent chains are also antiferromagnetically coupled.
Rational Synthesis of The Metastable Compounds BixCo4-xFexSb12
Authors: Williams Joshua R. , Hass Joanna , Sellinschegg Heike , Johnson David C.
Published: April 2011

The synthesis of many targeted ternary compounds using conventional synthesis approaches has been unsuccessful because the ternary compounds are thermodynamically unstable with respect to disproportionation to a mixture of binary compounds. Typically these compounds have been synthetic targets based on predictions of enhanced properties. The ternary skutterudites with formula M'xM4Sbl2 (where M' = La, Lu, Y) are prime examples. Compounds with this structure have been found to be very promising thermoelectric materials having both good electrical properties and low thermal conductivities. Inserting heavy M' atoms into this crystal structure has been predicted to further decrease the thermal conductivity by increased phonon scattering. Attempts to make the title compound using conventional synthesis approaches failed due the formation of binary compounds as reaction products. Using modulated elemental reactants we were able to prepare the title compound at 160°C. Annealing at temperatures above 500°C resulted in exothermic decomposition into binary compounds. The Bi containing compounds are therefore thermodynamically unstable with respect to disproportionation at all temperatures. The amount of Bi can be varied by varying the composition of the starting modulated elemental reactant. Preliminary measurements to determine the variation of electrical conductivity and Seebeck coefficient as a function of bismuth content are presented.
New Hydrides of Zr-Based Intermetallic Compounds
Authors: Zavaliy I. Y.
Published: April 2011

The promising hydrogenation properties of oxygen-stabilised qr-phases with filled-Ti2Ni structure type in Zr-M-O systems (M - V, Cr, Mn, Fe, Co, Ni) are shown in this work. Hydrogenation capacity of the representative examples of compounds with 1:1 and 2:1 metal/metal ratio – Zr3V3O and Zr4Fe2Ox – are presented on the dependence of oxygen content in order to discuss its influence on the hydrogen storage capacity of Zr-based η-phases. The hydrogen disproportionation of η-Zr4Fe2Ox as well as oxygenless pseudobinary (Zr0.6Hf0.4)2Fe compounds with the same structure was studied. The reducing of metal matrix stability with the decrease of oxygen content is shown and explained by the increase of the total energy of crystal lattice.
Iron (III) Oxide within Mesoporous MCM-48 Silica Phases: Synthesis and Characterization
Authors: Köhna R. , Bouffaud G. , Richard O. , van Tendeloo G. , Fröba M.
Published: April 2011

Using multiple cycles of wet impregnation, drying and calcination procedures it was possible to form haematite nanoparticles within the pore system of mesoporous MCM-48 silica phase. A decoration/coating of the inner surface of the silica walls was indicated by a reduction of the BET surface area, the pore radius as well as HRTEM and EDX investigations. Existence of small, slightly disordered iron (III) oxide nanoparticles was proved by X-ray absorption spectroscopic measurements.
Synthesis and Characterization of Nickel and Manganese Vanadium Oxides
Authors: Zhang Fan , Zavalij Peter , Whittingham M. Stanley
Published: April 2011

We have synthesized novel nickel and manganese vanadium oxides using the hydrothermal reactions of vanadium(V) pentoxide, Ni(CH3COO)2, and MnSO4 with an organic templating cation at 165°C. The [NH2(CH2)2NH2]2NiV6O14 has a monoclinic structure. It has some disordered V and 0 atoms in the V6014 layer, which appear to be very close to each other with occupation factor around 0.5. The disordered model was decomposed for two ordered configurations, which differ in the stacking of the layers. The (Mn+2)6(Mn+3)l−2/3z(OH)3(1−Z)(VO4)3[(VO4)l−2z(v207)z] (Z≈0. 1) phase has a hexagonal pipe morphology. These compounds were also characterized by electron microprobe, FTIR and TGA. They reacted readily with lithium, and their electrochemical behavior in lithium cells was determined.
Electron Microscopy Investigation of the Cycling-Induced Phase Transformation in LiMnO2 Compounds
Authors: Wang H. , Jang Y.-I. , Chiang Y.-M.
Published: April 2011

Lithium transition metal oxides used as intercalation electrodes for rechargeable lithium batteries are widely studied in search of structural stability and improved electrochemical performance. Recent studies showed that the orthorhombic and monoclinic LiMnO2 compounds, unlike LiMn204 spinels, could be cycled on both the 4 V and 2.9 V plateaus with high and stable discharge capacity. In this study, we have performed direct high resolution observations of electrochemically cycled LiMnO2 particles in the fully discharged state. Extensive damage including local strain variation, nanodomain formation, and changes in cation ordering, has been observed. Individual particles retain overall single crystallinity despite having differing structures at the nanodomain level. While cycling causes a macroscopic transformation to spinel cation ordering, the formation of nanodomains differing in cation ordering and/or composition appears to accommodate or prevent the destructive Jahn-Teller distortion that normally occurs at high lithium concentration, thereby resulting in cycling stability.
In situ Synchrotron X-ray Studies on Novel Mn Oxide Spinel Cathodes for Li-ion Batteries: Influence of Other Transition Elements
Authors: Mukerjee S. , Yang X. Q. , Sun X. , Lee S. J. , Mcbreen J. , Ein-Eli Y.
Published: April 2011

Partial substitution of Mn in lithium manganese oxide spinel materials by Cu and Ni greatly affects the electrochemistry and the cycle life characteristics of the cathode. Substitution with either metal or a combination of both shortens the 4.2 V plateau associated with the conversion of Mn3+ to Mn4+. A higher voltage plateau associated with oxidation of the substituted transition element is also observed. These substituent also significantly alter the onset of Jahn Teller distortions in the 3 V plateau. Synchrotron based in situ x-ray absorption (XAS) is used to determine the exact nature of the oxidation state changes in order to explain the overall capacities at the different voltage plateaus. Synchrotron based in situ x-ray diffraction (XRD) studies on LiCu0.5Mn1.504 shows single phase behavior in the 4-5 V region and a good cycle life. Lower cycle life characteristics for LiNi0.5Mn1.504 and LiNi0.25Cu0.25Mn1.504 are accounted for on the basis of several phase coexistence in this potential region. In the 3 V plateau however, the LiCu0.5Mn1.504 shows onset of the Jahn Teller distortions, in contrast to the LiNi0.5Mn1.504 and LNi0.25Cu0.25WMn1.504.
Electrochemical Feature of Hydrated Molybdenum Oxides in Lithium Batteries
Authors: Yebka B. , Julien C. , Nazri G.A.
Published: April 2011

Oxide-hydrates of molybdenum [OHM] are investigated as 3-volt cathode materials for rechargeable lithium batteries. The oxides and oxide-hydrates of molybdenum have been prepared at various degrees of heat treatment. The oxide-hydrates of molybdenum with different water content showed a much better performance as cathode of the rechargeable lithium battery than that of MoO3. From these results, it was found that the crystalline-bonded water molecules play an important role for the high discharge capacity and high cyclability. We report the electrochemical characteristics of Li/OHM batteries using the oxides and oxide-hydrates of molybdenum which have been prepared with various degrees of heat treatment of molybdic acid. The oxide has a corrugated layer structure consisting of corner-shared MoO6octahedra. This structure provide electronic conductivity within a layer and high lithium ion mobility between layers. The mechanism of dehydration and structural rearrangement of molybdic acid during heat treatment were studies by thermal analysis, X-ray diffraction, Raman and infrared spectroscopy. Thermal analysis indicates a two-step dehydration and formation of orthorhombic α-MoO3and monoclinic β-MoO3. Discharge profiles and kinetics of the materials are dependent on the amount of “structural water” into the host lattice. The electro-insertion of Li ions occurs mainly in two steps in the potential range between 3.0 and 1.5 V (compositional range 0<xLi<l.5). Kinetic measurement show that Li ions are highly mobile in the OHM framework. The partial molar quantities δGx, δSx, and δHx, estimated from EMF-temperature measurements and coulometric titration.
A Study of The Li|LixV2O4 Cell
Authors: Koval Eugen P. , Reshetnyak Olexander V. , Whittingham M. Stanley , Zavalij Peter Y. , Zavaliy Ihor Yu.
Published: April 2011

The studies of the Li | 1M LiClO4 in propylene carbonate | LixV2O4 cell were carried out. The results of the electrochemical and X-ray investigations indicated that the cathode reaction in this cell proceeds as an intercalation process. Cycling test shows the reversibility of this cell along 35 charge/discharge cycles. However X-ray diffraction of the electrode material shows partial oxidizing of the LixV2O4 phase yielding γ-LiV2O5. The kinetic parameters of this process such as the chemical diffusion coefficient and mobility of lithium in the LixV2O4 were calculated.
Hybrid Materials Based on Conducting Organic Polymers and Electroactive Inorganic Molecules and Oxides. Application as Lithium-Insertion Electrodes
Authors: Lira-Cantu M. , Torres-Gomez G. , Gomez-Romero P.
Published: April 2011

The synthesis, spectroscopic and electrochemical characterization of a series of hybrid organic-inorganic materials are reported. The hybrids are formed by conducting organic polymers (polyaniline, polypyrrole) and electroactive inorganic species. The latter can be either molecular anions (polyoxometalates, hexacyanoferrates) or extended oxide (V205), leading to different host-guest combinations. We have carried out a systematic study of the synthesis of the hybrids and determined key parameters for the reproducibility of the materials obtained. We have determined under what conditions the molecular species stay anchored in the polymer contributing to the overall electrochemical activity of these materials and turning the polymers from anion-insertion electrodes into cation-insertion electrodes. In the PAni/V2O5 system we have established the existence of two phases corresponding to the intercalation of one and two monolayers of PAni into V2O5 and have carried out their electrochemical characterization and their optimization as insertion cathodes in reversible lithium cells.
Investigation of Lithiated Carbons by Transmission Electron Microscopy and X-Ray Diffraction Analysis
Authors: Tran T. D. , Song X. Y. , Kinoshita K.
Published: April 2011

The microstructures of lithiated synthetic graphite and carbon black were studied by high- resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analysis. Information about the crystal structure of carbon containing various Li compositions can provide useful insights to our understanding of the Li storage mechanism in carbonaceous materials. Samples with compositions of Li0.93C6or Li0.45C6 were found to contain both stage-one and stage-two compounds. These observations are consistent with XRD data. The changes in sample microstructure as the results of lithiation and exposure to electron irradiation were observed by TEM and recorded over several minutes in the microscope environment. Selected area electron diffraction patterns indicated that the lithiated samples quickly changed composition to LiC 24, which appeared to dominate during the brief analysis period. The layer planes in the lattice image of a disordered carbon black after Li insertion are poorly defined, and changes in the microstructure of these lithiated carbons was not readily apparent. Observations on these lithium intercalation compounds as well as the limitation of the experimental procedure will be presented.
Concept of Mismatch and Relaxation Derived from Conductivity Spectra of Solid Electrolytes
Authors: Funke K. , Wilmer D.
Published: April 2011

Crystalline ion conductors like RbAg4I5 and others display a characteristic shape of their dispersive conductivities at frequencies below the microwave regime. As the temperature is decreased, the onset of the dispersion is shifted to lower frequencies and thus the characteristic shape of the dispersion becomes visible in an increasingly broad frequency range. In a log-log plot of the frequency-dependent conductivity, the slope is found to increase continuously, but not to surpass unity. For the first time, this behavior is now consistently explained. The particular shape of the dispersion is shown to be equivalent to a proportionality of the rates of relaxation via the singleand many-particle routes. This is the essence of the concept of mismatch and relaxation (CMR). Model conductivity spectra based on the CMR include the UDR (universal dynamic response) as well as the NCL (nearly constant loss) behavior. Both universalities are thus traced back to a common dynamic origin.
Thermal and Electrical Properties of Li20-V205-TeO2Glassy System
Authors: Sanchez E. , Angell C. A.
Published: April 2011

Oxide glasses had receive a great deal of attention on the last couple of years because of their potentially high cationic transport. Interesting features have been found on Li20-V205-TeO2glassy system. Such materials were prepared under open air at 800°C and traditional quenching. Glass formation was been found up to 45% alkali concentration on the V205-TeO2binary system. Upon addition of Li20 the glass transition temperature lowered systematically up to values near 175°C. Structural correlation between glass transition and structure are made. Those materials show high promise as electrolytes for solid-state batteries applications.