bluuebunny/crossref_metadata_2025 huggingface dataset:
Electromagnetic and Thermoelectric Characteristics of NaxCoO2 of Precisely Controlled Na Nonstoichiometry
Authors: Motohashi Teruki , Karppinen Maarit , Yamauchi Hisao
Published: April 2011

Electromagnetic and thermoelectric characteristics of a sodium-cobalt oxide, NaxCoO2, were investigated. A precise control of Na nonstoichiometry was successfully facilitated by an unusual synthesis method named “rapid heat-up” technique. With increasing x, the absolute value of resistivity (ρ) monotonically decreased, while the value of thermoelectric power (S) increased, giving rise to a drastic enhancement in the thermoelectric power factor, i.e. S2 / ρ. Simultaneously enhanced thermoelectric power and reduced resistivity of the present compound are difficult to be understood within the framework of a conventional band picture. Moreover, for samples with the solubility limit Na content, i.e. x = 0.75, we discovered an unconventional electronic transition at Tm = 22 K, which may be induced by the strong-correlation effect of 3d electrons.
Synthesis and Lattice Distortion of Ferroelectric/Antiferroelectric Bi(III)-containing Perovskites
Authors: Inaguma Yoshiyuki , Miyaguchi Atsushi , Katsumata Tetsuhiro
Published: April 2011

Bi(III)-containing perovskites Bi1/2Ag1/2TiO3and Bi(M1/2Ti1/2)O3(M= Co, Mg, and Ni) were synthesized under oxygen pressure as high as approximately 1 MPa and under a pressure as high as 6 GPa, and the lattice distortions were investigated. It was found that ferroelectric Bi1/2Ag1/2TiO3may be rhombohedrally distorted. In constrast, Bi(M1/2Ti1/2)O3(M= Co, Mg, and Ni), the structure of which is different from GdFeO3-type compound, is monoclinically distorted. The ratio of lattice parameters of the monoclinic perovskite-subcell for Bi(M1/2Ti1/2)O3(M= Co, Mg, and Ni),am/bmis larger than that of GdFeO3-type perovskites, though the tolerance factor is close. In addition, it was found that Bi(Ni1/2Ti1/2)O3undergoes a first-order phase transition from a GdFeO3-type phase(high-temperature phase) at around 490 K. These results indicate that the Bi3+character in Bi(III)-containing perovskites strongly influences the structure distortion.
Reinvestigation of the Incommensurate Structure of αPbO.
Authors: Baldinozzi Gianguido , Raulot Jean-Marc , Petricek Vaclav
Published: April 2011

Lead monoxide exists at room temperature in two forms, namely α-PbO, litharge (red, tetragonal) and β3-PbO massicot (yellow, orthorhombic). The weak bonds along the c axis and the ferroelastic nature of the incommensurate phase prevent the growth of single crystals suitable for high quality diffraction techniques (very small ferroelastic domains and frequent stacking faults in these layered structures). A structural determination of the incommensurate structure was proposed in the superspace group C2mb(0β;0) using the integrated intensities extracted from powder diffraction patterns. More recently an electron microscopy study suggested the existence of systematic extinctions affecting the satellite reflections and it supports the more symmetric space group Cmma(0β0)s. In this paper, high resolution powder diffraction patterns (synchrotron) were refined in the incommensurate phase using the Rietveld method. Various superspace groups and forms for the modulated displacements were tested. The consequences of this structural model on the electronic structure are analysed using also ab-initio calculations.
Commensurate-incommensurate phase transition in charge ordered La1-xCaxMnO3 by single crystal diffraction and electron imaging
Authors: Tao Jing , Murakami Y , Zuo Jian-min
Published: April 2011

Electron nanodiffraction from single crystal domain of La1-xCaxMnO3 with 0.5 ≤ × ≤ 0.8 is carried out to study the charge ordering phase transition in this system. The melting processes of charge ordering structure in samples with x = 1/2, 2/3 and 4/5 are observed in-situ by increasing temperature from 93K – 298K. During the phase transition, electron diffraction results show that the nearly commensurate low-temperature charge ordering structure continuously evolves to incommensurate structure with directly decreasing sizes of charge ordered area. The picture of this phase transition is confirmed by the real space imaging. The real space images clearly show the introduction of charge ordering defects during the melting process in this sample.
Epitaxial Growth of Magnetic Nickel Nanodots by Pulsed Laser Deposition
Authors: Zhou H. , Kumar D. , Kvit A. , Tiwari A. , Narayan J.
Published: April 2011

Epitaxial nickel magnetic nanodots were obtained by pulsed laser deposition (PLD) technique on Si (100) substrate using epitaxial TiN film as the template. Characterization methods include: high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) Z-contrast imaging, selected area electron diffraction (SAD), and X-ray diffraction (XRD) techniques. The results showed that as long as no coalescence between neighboring dots occurred, the dots are all single crystal. The predominant orientation relationship observed is Ni (100) // TiN (100) // Si (100), the so-called “cube-on-cube” orientation relationship. Other rotational orientation relationships, where the nickel crystal rotates an angle with respect to TiN (011) directions, were also observed. The dots are in faceted island shapes, bounded by (111) and (001) facets. The actual size of dots varies from a few nanometers to tens of nanometers, depending on the deposition time and temperature. The shape of a certain dot was found to be closely related to its epitaxial orientation. Effects of deposition temperature and template crystalline quality were studied. It was found that deposition temperature in a certain range does not have much influence on the epitaxial orientation of dots, while the crystalline quality of titanium nitride (the underlying template) is primarily responsible for the orientation variation. At the optimum condition, samples with a large fraction of cube-on-cube orientated nickel dots could be obtained in a rather wide temperature range (up to 250 °C), as evidenced by the strong reflections from both SAD and XRD. Samples containing more than one layer of nickel and titanium nitride matrix were also studied. The results showed that the degree of orientation perfection could be greatly improved by decreasing the size of dots.
Solid State Synthesis and Characterization of Tin-Based Low-Dimensional Materials
Authors: Salami Tolulope O. , Oliver Scott R. J.
Published: April 2011

We report the synthetic conditions, physical properties and potential applications of late group 14 metal (Sn) 0D, 1D, 2D and 3D extended materials. The structures are primarily neutral chain and anionic layered compounds. The latter are charge-balanced by ammonium cations, as in and BING-7 [Sn(C2O4)F-] [NH4+] and BING-8 [Sn(PO4H)F-] [NH4+]. The neutral layered compound and chain compounds BING-1 [Na4Sn4(C2O4)F6], BING-2 [KSn(C2O4)F] and BING-4 [Sn(C2O4)(C5H5N)] have also been synthesized solvothermally. Thermogravimetric analysis (TGA) under nitrogen and in-situ variable temperature X-ray diffraction show that the materials decompose in the 200°C to 300°C range to more stable phases. Nuclear magnetic resonance (NMR) was used to monitor the ion-exchange properties of some of the materials. The intercalation properties of these materials are still being investigated.
The Ternary System Li2O – Sb2O5 – CuO
Authors: Castellanos R María A. , Trujillo Tovar S.
Published: April 2011

Subsolidus compatibility relations in the ternary system Li2O – Sb2O5 – CuO have been determined. One new copper-rich phase, LiCu4SbO7, W, and one new solid solution series, Li1-xSb1-xCu3xO3, over the composition range 0 < × ≤ 0.077 have been prepared. Eight triangles of compatibility were determined at (approximately) 1000 °C.
Na+/H+ Topotactic Exchange on NaNbWO6 with TTB-like Structure: The series HxNa1-xNbWO6
Authors: Kuhn A. , García-Alvarado F. , Bashir H. , Dos Santos A. L. , Acosta J. L.
Published: April 2011

TTB-type NaNbWO6 has been used to perform sodium-proton exchange reactions by using nitric acid as an exchanging agent. The characterisation of the exchange reaction products, performed by means of chemical analysis, X-ray diffraction and thermogravimetric analysis, indicate that the exchange reaction takes place topotactically. The following formula is proposed for the obtained phase of variable composition: Na1-xHxNbWO6 (0<x<0.46).
Synthesis of a Metallic Ceramic -Ti3SiC2 by PDS Process and its Properties
Authors: Sun ZhengMing , Hashimoto Hitoshi , Zhang ZheFeng , Yang SongLang , Abe Toshihiko
Published: April 2011

Powder mixtures of Ti/Si/C, Ti/SiC/C, Ti/Si/TiC, Ti/SiC/TiC and Ti/TiSi2/TiC were used for the synthesis of Ti3SiC2 by using a pulse discharge sintering (PDS) process. The Ti/Si/TiC powder was found to be the best among the five powder mixtures for the Ti3SiC2 synthesis. The highest content of Ti3SiC2 can be improved to about 99wt% at the sintering temperature of 1300°C for 15 minutes. The relative density of all the synthesized samples is higher than 98–99% at the sintering temperature above 1275°C. The nearly single phase Ti3SiC2 was found to show plastic deformation at room temperature and a good machinability. Both electrical and thermal conductivity were found to be more than two times of the value of a control pure Ti sample. The high-temperature mechanical tests confirmed that the Ti3SiC2 samples synthesized by the PDS process displayed a comparable performance with those fabricated by the other techniques.
Thin Films of Titanium Dioxide Prepared by Chemical Routes using Novel Precursors
Authors: Shalini K. , Chandrasekaran S. , Shivashankar S.A.
Published: April 2011

Novel, volatile, stable, oxo-β-ketoesterate complexes of titanium, whose synthesis requires only an inert atmosphere, as opposed to a glove box, have been developed. Using one of the complexes as the precursor, thin films of TiO2 have been deposited on glass substrates by metalorganic chemical vapor deposition (MOCVD) at temperatures ranging from 400°C to 525°C and characterized by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. All the films grown in this temperature range are very smooth; those grown above 480°C consist of nearly monodisperse, nanocrystals of the anatase phase. Optical studies show the bandgaps in the range 3.4–3.7 eV for films grown at different temperatures. Thin films of anatase TiO2 have also been grown by spin-coating technique using another ketoesterate complex of titanium, demonstrating that the newly developed complexes can be successfully used for thin film growth by various chemical routes.
Designing Crystal Structures from Atoms up
Authors: Derakhshan Shahab , Dashjav Enkhtsetseg , Kleinke Holger
Published: April 2011

A novel structure map was developed for metal-rich pnictides and chalcogenides M2Q, with M being an element of groups 3 – 5, and Q of groups 15 – 16. To date, this family exhibits eleven different structure types, which are separated in well-defined domains in this structure map. The map comprises a combination of atomic factors as the abscissa, namely principal quantum numbers, valence-electrons, and radii, and a structural factor as the ordinate, which is the averaged coordination number of the Q atoms. We demonstrate in this contribution how this new map can be and has been used to predict crystal structures of new materials from atoms up. First attempts to expand this concept towards different stoichiometries are described.
Proton conductivity of functionalized zirconia colloids
Authors: Carrière D. , Moreau M. , Lahlil K. , Barboux P. , Boilot J.-P.
Published: April 2011

Colloidal 60 nm ZrO2 particles have been treated with aqueous solutions of phosphoric acid and sulphophenyl-phosphonic acid (SPPA). This leads to the covalent bonding of P-OH and C6H4-SO3H acid groups onto the surface of the particles. The resulting acidity yields a significant proton conductivity at the surface of the particles.

The proton conductivity of the ZrO2-H3PO4 system is quite stable against a change of relative humidity and temperature. However, it remains limited by the low acidity of the POH group. On the contrary, the proton conductivity of the ZrO2-SPPA system is almost two orders of magnitude higher at high relative humidities due to the high acidity of the C6H4-SO3H group (1.10-3 S.cm-1 in the same conditions). But, it is much more sensitive to changes in relative humidity.

A mixed grafting of both H3PO4 and SPPA onto the zirconia particles allows to obtain a conductivity as high as in the SPPA case whereas it remains stable with humidity and temperature as for the phosphoric acid. This probably indicates that the conductivity arises from ionization of sulphonic acid but that the weaker phosphoric acid groups contribute to the conduction mechanism.
Electrical Conductivity in Praseodymium-Cerium Oxide
Authors: Stefanik Todd S. , Tuller Harry L.
Published: April 2011

The electrical conductivity of PrxCe1-xO2-δ (PCO) for 0 ≤ × ≤ 0.20 was examined over a wide range of temperatures and oxygen partial pressures. A defect model based on multiple Pr valence states was found to be qualitatively consistent with the observed data. A unique pO2-dependent ionic conductivity is observed at high pO2 values in compositions containing low levels of Pr (0 ≤ × ≤ 0.01). In compositions containing higher amounts of Pr (0.05 ≤ × ≤ 0.20), formation of a Pr induced impurity band results in a significant electronic conductivity at high pO2 values.
The Synthesis and Characterisation of Ge Containing Apatite-Type Oxide Ion Conductors
Authors: Slater P. R. , Sansom J. E. H. , Tolchard J. R. , Islam M. S.
Published: April 2011

Apatite-type oxides, La10-x(Si/Ge)6O26+z, have been attracting significant interest recently due to their high oxide ion conductivities. Most of the work so far has focused on the Si based systems, since the Ge based systems suffer from problems attributed to Ge loss. In this paper we show that doping divalent cations on the La site or B on the Ge site helps to stabilise the hexagonal apatite lattice for these Ge based systems. These doped phases show high oxide ion conductivities, although results from extended sintering studies suggest that Ge loss is still a problem. In order to limit Ge loss, we have also examined Bi doping to lower the sintering temperature and preliminary results for the novel Bi containing apatite-type phases, La6Bi2M2Ge6O26 (M=Mg, Sr, Ba) and La8-xBi2Ge5GaO26+y, are also reported.
Phase Stability of Beta-gallia Rutile Intergrowths: (Ga,In)4(Sn,Ti)n-4O2n-2
Authors: Charoenwongsa Malin , Edwards Doreen D.
Published: April 2011

Beta-gallia-rutile (BGR) intergrowths possess one-dimensional tunnels that are suitable hosts for small-to-medium cations, thereby making them potential candidates for ion conductors, ion separators, battery electrodes, and chemical sensors. The BGR intergrowths are a series of homologous compounds expressed generically as Ga4Mn-4O2n-2, where n is an integer; and M is a tetravalent cation that forms a rutile-type oxide. In an attempt to identify materials with high tunnel densities and higher contents of a reducible M4+ cation, we are mapping the compositional stability regions of intergrowths expressed as Ga4–4xIn4xSn(n-4)(1-y)Ti(n-4)yO2n-2 where n = 6, 7 and 9 and 0.15 < x < 0.30 and 0 < y < 1.0. Polycrystalline samples were prepared by solid-state reaction at 1250 – 1400 °C and characterized by X-ray diffraction. Factors that affect phase stability are discussed.
Study of bare and functionalized Zirconia Nanoparticles Filled Polymer Electrolytes Based on a Polyurethane
Authors: da Conceição Paulo V. S. , Faria Luiz O. , Santos Adelina P. , Furtado Clascídia A.
Published: April 2011

In this work, composite polymer electrolytes based on a thermoplastic polyurethane/LiClO4 amorphous system and on bare and functionalized zirconia nanoparticles as a filler are reported. The ceramic nanoparticles were synthesized via the sol-gel route using zirconium butoxide as the precursor for zirconium oxide nanoclusters and methacrylic acid as an organic modifier group. The salt concentration in the polymer phase was 17 wt% and fillers were added in the range between 2 and 10wt%. Scanning electron microscopy (SEM) was used to characterize the average size and the homogeneity of the nanoparticles in the polymer matrix, while impedance spectroscopy (IS) was used to evaluate the ionic conductivity of the composites. The addition of zirconia fillers results in an increase in ionic conductivity for all filled systems. The results also show that the functionalization of the zirconia nanoparticles promotes a significant increase in conductivity, suggesting that the interaction of the metracrylate-functionalized fillers with the polyurethane matrix was greatly improved. These results raise interest in the study of organically modified ceramic clusters as fillers for electrolyte polymers.
Cation Ordering in Substituted LiMn2O4 Spinels
Authors: Strobel P. , Ibarra-Palos A. , Poinsignon C.
Published: April 2011

In order to overcome the capacity fading of LiMn2O4 in lithium batteries, various substitutions for Mn have been proposed. The structural implications of substitution in LiMn2-xMxO4 with x = 0.5, i.e. with exactly 1/4 octahedral (16d-site) cations replaced, are investigated here. For this stoichiometry, cationic ordering was known previously for M = Mg and Zn, resulting in a superstructure with primitive cubic symmetry. Given the poor chemical contrast of X-ray diffraction between Mn and Co, Ni or Cu, LiMn1.5M0.5O4 samples were studied by neutron diffraction and IR spectroscopy. Both techniques show the occurence of cationic ordering for M = Ni and Cu, but not for Co or Ga. In the case of M = Zn, further complication due Li/Zn ordering on the tetrahedral (8a) site is well resolved by FTIR. This investigation shows that the main driving force for octahedral cation ordering is the charge difference between Mn and M atoms.
Enhanced Ionic Conduction Observed for Ordered-Mesoporous Alumina-Ionic Conductor Composites
Authors: Maekawa Hideki , Tanaka Ryo , Yamamura Tsutomu
Published: April 2011

Ordered-mesoporous Al2O3 was synthesized by the sol-gel method using neutral surfactants as templates. The pore size can be controlled over the range of 2.8∼12.5 nm by using different surfactant copolymers and by different synthetic conditions. By utilizing cyclohexane as a co-solvent, mesoporous Al2O3 having relatively mono-dispersed particle size was obtained. Composites composed of the synthesized mesoporous Al2O3 and the lithium ion conductor (LiI) was prepared. The dc electrical conductivity of 50LiI ·50(mesoporous Al2O3) was 2.6×10-4 S cm-1 at room temperature, which is more than 100 times higher than that of pure LiI. The pore size dependence of the conductivity of LiI-mesoporous Al2O3 composite was examined. A systematic dependence of conductivity upon pore size was observed, in which the conductivity increased with decreasing the pore size.
Ball-milling: an alternative way for the preparation of anodes for lithium-ion batteries
Authors: Guérard Daniel , Janot Raphaël
Published: April 2011

The preparation of new anodic materials for lithium-ion batteries is possible by ball-milling within liquid media. Those powders can be as diverse as: highly anisometric graphite particles (geometrical anisotropy around 100), graphite-maghemite (γ Fe2O3) composites and graphite-intercalation compounds with high lithium contents (e.g. LiC3 is obtained by ball-milling of Li + 2C powders). These phases are the first superdense graphite-lithium compounds stable under ambient pressure and lead to a capacity of 1 Ah/g as primary battery and 370 mAh/g as secondary one. The synthesis and characterizationschemical analysis, XRD, pycnometry, TEM, SEM, 7Li NMR, magnetic measurements) are presented for each materials as well as the electrochemical behavior.
Initial growth stages of CeO2 nanosystems by Plasma-Enhanced Chemical Vapor Deposition
Authors: Barreca Davide , Gasparotto Alberto , Tondello Eugenio , Polizzi Stefano , Benedetti Alvise , Sada Cinzia , Bruno Giovanni , Losurdo Maria
Published: April 2011

Nanocrystalline CeO2 thin films were synthesized by Plasma-Enhanced Chemical Vapor Deposition using Ce(dpm)4 as precursor. Film growth was accomplished at 150–300°C either in Ar or in Ar-O2 plasmas on SiO2 and Si(100) with the aim of studying the effects of substrate temperature and O2 content on coating characteristics. Film microstructure as a function of the synthesis conditions was investigated by Glancing Incidence X-Ray Diffraction (GIXRD) and Transmission Electron Microscopy (TEM), while surface morphology was analyzed by Atomic Force Microscopy (AFM). Surface and in-depth chemical composition was studied by X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectrometry (SIMS).
Enhanced Graphite Fiber Electrodes for a Microbial Biofuel Cell Employing Marine Sediments
Authors: Konesky Gregory
Published: April 2011

A microbial biofuel cell has been demonstrated utilizing organic material in the sediment as fuel and dissolved oxygen in the overlying seawater as the oxidizer. A graphite electrode placed in the sediment acts as the anode and collects electrons both by mediated and non-mediated processes. Another graphite electrode suspended in the seawater above the sediment acts as the cathode and transfers these electrons to oxygen in the seawater. The sediment serves as a natural permeable membrane that permits hydrogen ions to flow from within the sediment and combine with the oxygen to produce water. Electrons which flow from the anode to the cathode through an interconnecting wire are used to power external circuits. Both fuel and oxidizer are naturally present and self-renewing, and the graphite electrodes are inexpensive and non-toxic. Overall, this is a very “green” fuel cell. A significant improvement in collection efficiency is demonstrated by using graphite fiber electrodes.
Nucleation And Growth of Yttria-Stabilized Zirconia Thin Films Using Combustion Chemical Vapor Deposition
Authors: Xu Zhigang , Sankar Jag , Yarmolenko Sergey , Wei Qiuming
Published: April 2011

Liquid fuel combustion chemical vapor deposition technique was successfully used for YSZ thin film processing. The nucleation rates were obtained for the samples processed at different temperatures and total-metal-concentrations in the liquid fuel. An optimum substrate temperature was found for the highest nucleation rate. The nucleation rate was increased with the total-metal-concentration. Structural evolution of the thin film in the early processing stage was studied with regard to the formation of nuclei, crystallites and final crystals on the films. The films were found to be affected by high temperature annealing. The crystals and the thin films were characterized with scanning electron microscopy.
Metal Dusting Problem with Metallic Interconnects for Solid Oxide Fuel Cell
Authors: Zeng Z. , Natesan K.
Published: April 2011

Metallic interconnects in the solid oxide fuel cell (SOFC) are oxidized on the cathode side by air and carburized on the anode side by natural gas. Metallic alloys can be attacked by metal dusting corrosion in carbonaceous gases of high carbon activity in the temperature range of 350–1000°C. Under these conditions, pits form on the alloy surface and can become large holes through the alloy plate, with subsequent disintegration into a powdery mixture composed of carbon, fine particles of metal, and carbide. Fe and Ni-base alloys were tested in carbonaceous gases around the SOFC operating temperature. It was found that the oxide scales on the alloy surface prevent metal dusting corrosion. If the major phase in the oxide scale is chromic oxide, the alloys have good resistance to metal dusting corrosion. However, the alloys are easily attacked if the major phase is spinel.
Self-Assembly of Iron Nanoparticle Arrays
Authors: Majetich S. A. , Farrell D. F.
Published: April 2011

Surfactant-coated spherical iron-based nanoparticles 3.0–9.5 nm in diameter were synthesized and dispersed in hexane. TEM images of dried particle assemblies were taken and analyzed to discover the structure of the assemblies, and to establish the relationship between particle concentration, surfactant type, and conditions of drying and array structure.
The Effect of a Non-Equipartition of Energy on Multi-component Flows
Authors: Galvin J. E. , Dahl S. R. , Hrenya C. M.
Published: April 2011

Rapid granular flows of two species with different material densities are examined via three-dimensional, hard-sphere simulations of simple shear flow. Simulation results are compared with existing theories for binary systems based on the kinetic theory analogy. The comparison between simulation data and theoretical predictions indicate that although non-equipartition is observed and well-predicted by the theory which accounts for its effects, the influence of non-equipartition on stress predictions is fairly small. The influence of non-Maxwellian effects, however, are critical for accurate stress predictions.
Development of shear bands in annular shear granular flows
Authors: Jalali Payman , Li Mo
Published: April 2011

Using hard-disk simulations of relatively dense packs of mono-sized system in an annular Couette geometry the formation of dilute regions inside the granular media, namely shear bands, are investigated. The results represent the influence of entire system characteristics such as solid area fraction and shear rate on the development of shear bands as well as the local properties of grains that cause them to participate in the formation of a shear band. Moreover, simulations have been performed for binary-sized system, which revealed that the formation of such diluted shear bands is unlikely.
Mechanical Behavior Of Energetic Materials During High Acceleration
Authors: Lanzerotti Y. , Sharma J.
Published: April 2011

The mechanical behavior of explosives subjected to high acceleration has been studied in an ultracentrifuge at –10°C and 25°C. Melt-cast TNAZ and pressed TNAZ, LX-14, Composition A3 Type II, PAX-2A, and PAX-3 have been studied. Failure occurs when the shear or tensile strength of the explosive is exceeded. The fracture acceleration of melt-cast TNAZ is greater than that of pressed TNAZ at –10°C and 25°C. The fracture acceleration of PAX-3 is greater than that of Composition A3 Type II at –10°C and 25°C. The fracture acceleration of melt-cast TNAZ and pressed TNAZ at –10°C is about 10% less than at 25°C. The fracture acceleration of PAX-3 at –10°C is about 2.6 times that at 25°C. The fracture acceleration of Composition A3 Type II at –10°C is about 1.7 times that at 25°C.
Managing Student Group Projects in an Introductory Materials Science Course
Authors: Isaacs Jacqueline A.
Published: April 2011

In an introductory materials science course for mechanical and industrial engineering sophomores, a term-long student team project is included as a graded activity. Successful completion of the project fulfills three course objectives where students learn 1) to compose professional reports in teams and demonstrate effective communication skills, 2) to apply introductory concepts of materials science well enough to follow technical articles on various topics, and 3) to locate resources to gather additional information related to a topic. To help students learn to research a topic, to write, to work in teams, and to speak publicly, the course includes guest lectures with various instructors with expertise in library research skills, technical writing, and communication studies. Course assessment indicates that sophomores find their projects interesting and they report learning a lot about the topics they selected. Interventions in the early stages of the curriculum allow the students to perform better during their senior year Capstone Design Project. The details of how the projects are managed will be described.
A Multi-functional Introductory Materials Science Course: Emphasizing Engineering and Achieving Accreditation Objectives
Authors: Chen Katherine C. , Vanasupa Linda S. , Orling Timothy T.
Published: April 2011

In efforts to serve more engineering students and to achieve accreditation objectives, we have redesigned our introductory materials course to be more engineering-oriented and relevant to other disciplines. The fundamental materials science concepts have been regrouped into five, 2-week sections that emphasize applications: Materials Basics; Mechanical Strength; Thermo-mechanical Treatments; Electrical Properties; and Economic, Environmental and Societal Issues. Although the topics that are covered are similar to those in most introductory materials science courses, the presentation of the topics has been re-arranged to create clearer links between materials science and materials engineering. We have also identified accreditation criteria within each section and have built in mechanisms for providing feedback for accreditation processes. In addition, learning objectives for each section ensure standardization among different sections and instructors. Results on students' performances are reported.
Microscopic study of electrical transport through single molecules with metallic contacts: Organic molecules and finite carbon nanotube
Authors: Xue Yongqiang , Ratner Mark A.
Published: April 2011

We present microscopic study of electronic and transport properties of single molecules sandwiched between two metallic contacts using Green's function based modeling approach within both ab initio and self-consistent semi-empirical framework. The methods are applied to thiol-based organic molecules and finite-size single-wall carbon nanotubes respectively. Results on electrostatics, transmission and current-voltage characteristics are presented.
Conductance Microscopy for Electric Conduction Study of Bio-Inspired Hybrid Nanostructures under Ambient Conditions
Authors: Setyawan Wahyu , Rao Saleem , Hong Seunghun
Published: April 2011

Electrical conductance of single stranded DNA (5′-TTT TTT TTT T/3 Thio MC3-D/-3′) monolayer patterns on Au surface is compared with those of various organic molecular patterns via the conductance microscope (CM) technique that allows one to take nanoscale conductance images utilizing a conducting AFM tip in contact mode AFM. In the experiment, reference molecules and ssDNA are patterned on the same substrate via direct deposition methods such as dip-pen nanolithography and microcontact printing. Then, conductance microscope image is recorded revealing the relative conductivity of ssDNA patterns relative to various reference molecules. 16-mercaptohexadecanoic acid and 2-mercaptobenzimidazole patterns are found conducting better than the ssDNA patterns. This result indicates that the ssDNA with 10T bases is a relatively poor electrical conductor. The capabilities of CM technique are also tested on various nanostructures including the single wall carbon nanotube junction.
Focused Ion Beam Nano-Machined Structures For Strain Analysis By A Moiré Technique
Authors: Li Biao , Xie Huimin , Zhang Xin
Published: April 2011

The accurate determination of residual stress/strain in thin films is especially important in the emerging field of MicroElectroMechanical Systems (MEMS). In this article, a focused ion beam (FIB) moiré method is proposed and demonstrated to measure the strain in MEMS structures. This technique is based on the advantages of the FIB system in nano-fabrication, imaging, in-situ deposition, and fine adjustment. Nano-grating lines with 70 nm width and 140 nm spacing are directly written on the top of the MEMS structures by ion milling without the requirement of an etch mask. The FIB moiré pattern is formed by the interference between a prepared specimen grating and FIB raster scan lines. The strain of the MEMS structures is derived by calculating the average spacing of moiré fringes. Since the local strain of a MEMS structure itself can be monitored during the process, the FIB moiré technique has many potential applications in the mechanical metrology of MEMS. As an example, the strain distribution along the sticking MEMS structures, and the contribution of surface oxidization and mass loading to the cantilever strain is determined by this FIB moiré technique.
High-Q integrated RF passives and RF-MEMS on silicon
Authors: van Beek Joost T.M. , van Delden Marc H.W.M. , van Dijken Auke , van Eerd Patrick , Jansman Andre B.M. , Kemmeren Anton L.A.M. , Rijks Theo G.S.M. , Steeneken Peter G. , den Toonder Jaap , Ulenaers Mathieu J.E. , den Dekker Arnold , Lok Pieter , Pulsford Nick , van Straten Freek , van Teeffelen Lenhard , de Coster Jeroen , Puers Robert
Published: April 2011

A technology platform is described for the integration of low-loss inductors, capacitors, and MEMS capacitors on a high-resistivity Si substrate. Using this platform the board space area taken up by e.g. a DCS PA output impedance matching circuit can be reduced by 50%. The losses of passive components that are induced by the semi-conducting Si substrate can effectively be suppressed using a combination of surface amorphisation and the use of poly crystalline Si substrates. A MEM switchable capacitor with a capacitance switching factor of 40 and an actuation voltage of 5V is demonstrated. A continuous tuneable dual-gap capacitor is demonstrated with a tuning ratio of 9 using actuation voltages below 15V.
Passive Isolators Based On Barium Ferrite Sputtered Films
Authors: Le Berre M. , Capraro S. , Chatelon J. P. , Joisten H. , Rouiller T. , Bayard B. , Barbier D. , Rousseau J. J.
Published: April 2011

Ferrites have magnetic properties suitable for electronic applications, especially in the microwave range (circulators and isolators). Hexagonal ferrite, such as barium ferrite (BaFe12O19 or BaM), are of great interest for microwave device applications because of their large resistivity and high permeability at high frequencies.

This contribution focuses on BaM films, 1 to 10 microns thick, which were deposited under optimized conditions by RF magnetron sputtering on alumina or silicon substrates. In order to crystallize the films that were amorphous after deposition, a post deposition annealing at 800°C was implemented. Optimized samples presented a good crystallization, a smooth surface and no cracks. The films were either randomly oriented or showed slight preferential orientations among the crystallographic planes (101), (200), (206), (102), (110) and (205) when the substrates were heated up to 400°C during the deposition. Ba, Fe and O depth profiles obtained by Secondary Ion Mass Spectroscopy (SIMS) showed that the films have a good in-depth uniformity. The magnetic properties of BaM films determined by VSM, showed that the optimized coercive force and the saturation magnetization reached 330 kA/m and about 500 mT respectively. These values are closed to that of the bulk BaM.

Isolators were then realized using patterning of coplanar metallic lines with standard lift-off technique. The slots and the central width were set to 300 μm, gold was used for the lines. First results on transmission coefficients showed a non reciprocal effect, which reaches 3.3 dB/cm at 50 GHz. This proved that such a component behaves like an isolator in the 50 GHz band.
Pulsed DC Reactive Magnetron Sputtering of AlN Thin Films on High Frequency LTCC Substrates
Authors: Lee Jung W. , Cuomo Jerome J. , Moody Baxter F. , Cho Yong S. , Keusseyan Roupen L.
Published: April 2011

This preliminary work reports the preparation of AlN thin films on an LTCC (low temperature co-fired ceramics) substrate by pulsed dc reactive magnetron sputtering and the limited characterization focusing on microstructure and crystal orientation. The main focus will be placed on the effects of changing pulsed frequency. The AlN thin film showed good adhesion with the substrate and columnar structures having small grains regardless of pulsed frequency. The crystal orientation of AlN thin films was dependent on pulsed frequency according to the result of XRD patterns. The preferred (002) orientation was obtained at a pulsed frequency of 100 kHz. The broad band of 300 to 650 nm observed in photoluminescence spectrum was believed due to defects associated with the presence of oxygen impurities.
The Microstructures and Grain Boundary Segregations of Ceramic Barium Titanate Processed in Microwave Field
Authors: Liu Hanxing , Tian Zhongqin , Zhou Jian , Yu Hongtao , Zou Long , Ouyang Shixi
Published: April 2011

Ceramic sintering in microwave field is a new ceramic processing method. In present paper, we detected the microstructures and boundary segregation of BaTiO3 ceramics which were sintered in microwave field. Scanning electron microscopy(SEM), and transmission electron microscopy(TEM), and chemical analysis methods were employed to detect the microstructure of BaTiO3, element distribution near the boundary of BaTiO3 ceramic. The results shown growth of grain of the ceramic was influenced by impurities such as acceptor, benefactor et al, and the element distribution near the grain boundary of BaTiO3 sintered in microwave field were different with that sintered in conventional method. The boundary segregations of BaTiO3 sintered in microwave field were not obvious as compared to the conventional method because the diffusion was enhanced due to the microwave field.
Growth Model of Epitaxial Pb(Zr0.52Ti0.48)O3 Nanoislands
Authors: Chu Ming-Wen , Szafraniak Izabela , Scholz Roland , Hesse Dietrich , Alexe Marin , Gösele Ulrich
Published: April 2011

Single-crystalline, single-c-domain Pb(Zr0.52Ti0.48)O3 nanoislands (truncated-pyramid in shape) with an average height of ∼9 nm and a base length of ∼50 nm were grown on compressive niobium-doped SrTiO3(001) substrates using chemical solution deposition. Cross-sectional highresolution electron microscopy investigations allowed to propose a growth model of the islands, and they proved the existence of edge-type misfit dislocations at the interface.
Shape of piezoelectric hysteresis loop for non-ferroelastic switching
Authors: Tagantsev A. K. , Muralt P. , Fousek J.
Published: April 2011

A simple theory for the shape of the piezoelectric hysteresis loops (piezoelectric coefficient d vs. applied electric field E) is developed for the case of non-ferroelelastic 180° switching in ferroelectrics. The theory provides explanations for specific features of piezoelectric hysteresis loops, which have been observed in single crystals, thin films and in ceramics in particular. The piezoelectric coefficient may show a “hump”, i.e. when E decreases from the tip of the loop down to zero, d passes through a maximum, and a “nose”, i.e. a self-crossing of the loop close to its tips. The theory also explains the difference in the coercive fields seen in the polarization and piezoelectric loops.
Local Hysteresis Behavior of Ferroelectric Thin Films of Si added PbTiO3
Authors: Palkar V. R. , Higgins M. , Purandare S. C. , Pinto R. , Bhattacharya S.
Published: April 2011

We report ferroelectric properties and local hysteresis behavior of 2 mole percent Si added PbTiO3 thin films grown on Pt/TiO2/SiO2/Si substrate by using pulsed laser deposition technique. The ferroelectric hysteresis loop and scanning piezoresponce images obtained on these films by using AFM with conducting tip demonstrate excellent properties, which are equivalent to any other established ferroelectric material like PZT. Si segregating at the grain boundaries controls grain growth. The grain size and grain boundaries play a crucial role in determining ferroelectric hysteresis properties. The presence of Si in the matrix can be useful in tuning the properties.
Comparison of Titanium Precursors in the Sol-Gel Synthesis of Pb0.5Ba0.5TiO3 Powders and Thin Films
Authors: Boland Stacey W. , Haile Sossina M.
Published: April 2011

Two sol-gel processes for producing Pb1-xBaxTiO3 (PBT), a ferroelectric material of interest for sensor and actuator applications, are investigated. Each system incorporates lead nitrate and barium acetate as metal sources and ethylene glycol as a solvent. Diethanolamine is used as a chelating agent for titanium isopropoxide or titanium butoxide. Precursor chemistry was systematically varied and the resulting sols and powders were studied using TGA/DSC, FTIR, and XRD. Thin films were prepared using both precursor sources by spin coating onto single crystal (100) MgO. Spin speed and pyrolysis temperature were optimized to produce oriented thin films with thicknesses of up to approximately 500nm. Sols incorporating titanium isopropoxide and a large excess of diethanolamine were particularly stable against hydrolysis.
Laser Annealing of Ferroelectric SrBi2Ta2O9, Pb(ZrXTi1-X)O3 and CeMnO3 Thin Films
Authors: Sbrockey N. M. , Cuchiaro J. D. , Provost L. G. , Rice C. E. , Sun S. , Tompa G. S. , DeLeon R. L. , Kalkur T. S.
Published: April 2011

Excimer laser annealing studies were conducted of SrBi2Ta2O9, Pb(ZrxTi1-x)O3 and CeMnO3 thin films. The main incentive was to develop a low temperature process for SrBi2Ta2O9 thin films, which typically require a 750 C anneal to crystallize and achieve optimum ferroelectric properties. The results show that room temperature laser annealing can crystallize SrBi2Ta2O9, with a strong (200) preferred orientation. The Pb(ZrxTi1-x)O3 and CeMnO3 thin films investigated in this study were crystalline as deposited. Laser annealing of the Pb(ZrxTi1-x)O3 and CeMnO3 films did not result in a significant increase in crystallinity, as evidenced by the intensities of the x-ray diffraction peaks. Electrical characterization of laser annealed SrBi2Ta2O9 thin films showed good dielectric properties and the onset of ferroelectric behavior. Low temperature laser annealing is shown to be a viable approach to enable integration of ferroelectric SrBi2Ta2O9 films with silicon based micro-electronics, for ferroelectric memory applications.
Effect of Deposition Parameters on the Microstructural Evolution and Electrical Properties of Charge-Balanced Barium Strontium Titanate Ferroelectric Thin Films Deposited on Ceramic Substrates by Pulsed Laser Deposition
Authors: Fountzoulas Costas G. , Tidrow Steven C. , Hatzistergos Michael , Efstathiadis Harry
Published: April 2011

Barium strontium titanate (Ba0.60Sr0.40TiO3) thin films are the main materials of interest in tunable phase shifter for microwave antenna applications. Ba0.60Sr0.40Y0.05Ta0.05Ti0.90O3 thin films, of nominal thickness ranging from 1.7 μm to 2.3 μm, were synthesized on MgO (100) substrates, at substrate temperatures ranging from 500°C to 900°C, at oxygen partial pressures 20 and 50 mTorr, at 500 mJ energy fluence on 3 mm x 1 mm spot size and 10 pulses per second using the pulsed laser deposition technique. All film synthesized at temperatures greater than 500°C were crystalline. The effect of the ionic substitution and substrate temperature in conjunction with the effect of the oxygen partial pressure on the microstructure, and mechanical and electrical properties of the thin films have been studied using shallow angle x-ray diffraction, SEM, nanoindentation, atomic force microscopy (AFM), and focused ion beam analysis (FIB) and are reported in detail. We are currently in the process of measuring the capacitance of these films by various methods.
Ferroelectric and Ferromagnetic Properties of BiFeO3 Thin Films Deposited by Pulsed Laser Deposition
Authors: Yun Kwi-Young , Noda Minoru , Okuyama Masanori , Saeki Hiromasa , Tabata Hitoshi
Published: April 2011

BiFeO3 thin film has been prepared on Pt/TiO2/SiO2/Si substrate at a temperature as low as 450°C by pulsed-laser deposition. The BiFeO3 thin film is perovskite single-phase, while any nonperovskite phase, such as orthorhombic Bi2Fe4O9, is not included. Dielectric constant of the film is 87, dielectric loss is 0.03, and leakage current density is low. The coexistence of ferroelectricity and ferromagnetism has been confirmed by means of the P-E and M-H hysteresis characteristics. The BiFeO3 thin film shows a well-saturated hysteresis loop with twice the remanent polarization 2Pr = 54 μC/cm2 and coercive field 2Ec = 100 kV/cm for a maximum applied electric field of 100 kV/cm, and also shows a saturated weak ferromagnetic hysteresis loop, as well as a small remanent magnetization with 2Mr = 0.6 emu/cm3 and 2 Hc = 200 Oe for a maximum magnetic field of 10 kOe at room temperature.
First-principles study of the electronic structure of Pb(ZrTiNb)O3 (PZTN) systems
Authors: Miyazawa Hiromu , Higuchi Takamitsu , Aoyama Taku , Kijima Takeshi , Natori Eiji , Shimoda Tatsuya , Oguchi Tamio
Published: April 2011

Using first principles calculations, we have investigated the electronic structure of Pb(ZrTiNb)O3 (PZTN), a system with a low leakage current and high reliability in thin films. We proposed that in PZTN, the oxygen vacancy is suppressed due to the addition of a Nb atom at the B site and that this change prevents a bandgap narrowing which would enhance the leakage current. The oxygen vacancy in the perovskite structure reduces the bandgap because it lowers the d orbital energy of the nearest-neighbor transition metal through the Madelung potential; this bandgap narrowing induces the leakage current in conventional Pb(ZrTi)O3 (PZT) systems with the Shottky type Pb-O deficit. In contrast, the PZTN systems, which also have the Pb deficit but lack the oxygen vacancy, can maintain the bandgap, and attain a low leakage current.
Effect of Cationic Substitution on Raman Spectra of SrBi2Ta2O9Ceramics and Thin Films
Authors: Perez W. , Das R. R. , Dobal P. S. , Yuzyuk Y. I. , Bhattacharya P. , Katiyar R. S.
Published: April 2011

In the present work micro-Raman spectroscopy has been used to understand the lattice dynamics of cation substituted SBT ceramics and thin films. Different concentrations of Ca and V were introduced into SBT lattices. Incorporation of Ca ion at Sr-site was confirmed by decrease in the lattice parameters calculated from x-ray diffraction data. The lowest Raman modes at 27 cm-1and 58 cm-1showed upward shift with increasing Ca concentration and was attributed to the lower mass and lower ionic radii of Ca. The temperature dependant Raman studies revealed the increase of the phase transition temperature with increased Ca content, and was attributed to the decrease in tolerance factor. Substitution of smaller cation at Sr site in SBT compound has increased lattice mismatch between SrO and TaO2planes inside the stable perovskite unit of SrTa2O7which has pronounced influence on ferroelectric properties of SBT. Substitution of vanadium at Ta-site of SBT did not influence the low frequency Raman modes of SBT. However, it showed a pronounced influence on the O-Ta-O stretching modes by splitting the mode frequency at 810 cm-1. The transition temperature of SBT was reduced with increasing vanadium contents.
Effect of Thermal Strain on Domain Fraction in a-/b-axis-oriented Epitaxial Bi4Ti3O12 Films
Authors: Watanabe Takayuki , Morioka Hitoshi , Okamoto Shoji , Takahashi Masatake , Noguchi Yuji , Miyayama Masaru , Funakubo Hiroshi
Published: April 2011

a-/b-axis-oriented epitaxial Bi4Ti3O12 and neodymium-substituted Bi4Ti3O12 films with a different a-domain fraction, V(100)/[V(100)+V(010)], were grown by metalorganic chemical vapor deposition above the phase transition temperature. It was demonstrated that the saturation polarization observed for the a-/b-axis-oriented film is proportional to the a-domain fraction estimated by x-ray diffraction. The liner relationship passing through the origin revealed that the 90° domain switching by an external electric field hardly occurred. The extrapolation gave spontaneous polarization of 58 μC/cm2 for a pure a-axis-oriented (Bi3.5Nd0.5)Ti3O12 film. The domain fraction was investigated as a function of thermal strain originated from a difference in thermal expansion coefficient between the film and substrates. The domain fraction of the films changed with the thermal strain along the in-plane [010] in tetragonal a-axis-oriented films as well as epitaxially grown tetragonal Pb(Zr,Ti)O3 films.