bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improvement of Thermal Stability of Metal/Oxide Interface for Electronic Devices
Authors: Ichikawa Yo , Hiramoto Masayoshi , Matsukawa Nozomu , Iijima Kenji , Kitagawa Masatoshi 
Published: April 2011

ABSTRACTThe nano-meter controlled iron/iron-oxide multilayer materials have been successfully obtained by the pulse reactive sputtering method with high deposition rate. These multilayer demonstrated a good thermal stability of its structure and magnetic properties up to 500°C when a small amount of Si was doped in the structure, whereas the non-doped multilayer degraded at above 300°C. The difference of the oxidation energy between Fe and Si increases the thermal stability of the interface between Fe and Fe-O layer.
Crystallinity and Magnetoresistance in Calcium Doped Lanthanum Manganites
Authors: Gillman E. S. , Dahmen K. H. 
Published: April 2011

ABSTRACTThin films of calcium doped lanthanum manganites Lal-xCaxMnO3 (LCMO) with x ∼ 0.41 have been prepared on LaAlO3(001) (LAO) Y-stablized ZrO2(001) (YSZ), and Al2O3(0001) (SAP) substrates by liquid delivery metal-organic chemical vapor deposition (LD-MOCVD). The films on YSZ and SAP substrates have a textured, polycrystalline morphology with a preferred orientation of (110). The films on LAO show a single-crystalline morphology and a (100) orientation. Transport measurements show the polycrystalline films have a resistance peak approximately 60K lower than the films on LAO and, in general, have a much higher overall resistance. The magne-toresistance (MR) ratio ([R(H) - R(0)]/R(H)) is sharply peaked near the maximum in resistance for the films on LAO, while the polycrystalline films show a noticeable absence of this sharply peaked behavior and a flat, rather large (∼ 100%) MR ratio over a large temperature range. These results will be discussed in terms of grain boundary scattering, crystallite size, and magnetization.
Low Energy K-Dependent Electronic Structure of the Layered Magnetoresistive Oxide La1.2Sr1.8Mn2O7
Authors: Saitoh T. , Dessau D. S. , Park C.-H. , Shen Z.-X. , Villella P. , Hamada N. , Moritomo Y. , Tokura Y. 
Published: April 2011

ABSTRACTWe have studied the fc-dependent electronic structure of the layered colossal magnetoresistive manganite La1.2Sr1.8Mn2O7 using high-resolution angle-resolved photoemission spectroscopy. We found dispersive energy bands as a function of the crystal momentum k near the Fermi level (EF). We have also performed local spin density approximation (LSDA)+U band-structure calculations on the current system. The overall experimental dispersion relation is basically in agreement with the band-structure calculations yet close to EF there is a significant deviation from the predicted dispersions. Instead of clear Fermi-surface (FS) crossings, we observe a depression of the features as the FS is approached as if there is a “pseudo” gap in the excitation spectrum. The pseudogap continuously opens with temperature and does not show further significant opening above Tc, corresponding to the metal-insulator transition. Those unusual aspects of the spectra has been discussed from the viewpoint of the strong electron-lattice coupling model.
Observation of Growth-Related Magnetic Structures in La0.67Sr0.33MnO3
Authors: Hawley M. E. , Brown G. W. , Kwon C. 
Published: April 2011

ABSTRACTAmbient observation of magnetic structures by magnetic force microscopy (MFM) in La0.67Sr0.33MnO3 films has not yet been clearly correlated with stresses induced by the kinetic or thermodynamic growth processes or the compressive (LaAlO3) or tensile (SrTiO3) nature of the substrate lattice-mismatch. Although domain-like magnetic structures have been seen in some as-grown films on LAO and related to substrate-induced stress and film thickness, no magnetic structure has been seen for films on STO and other films grown under different kinetic conditions on LAO. In this study we have identified a set of pulsed-laser deposition conditions with the substrate temperature as a variable to determine the relationship between growth and stress-induced magnetic structures. Results from scanning tunneling, atomic force, and MFM microscopies, magnetization, and coercivity measurements will be presented.
Effects of Localized Holes on Charge Transport, Local Structure and Spin Dynamics in the Metallic State of CMR La1-xCaxMnO3
Authors: Heffner R. H. , Hundley M. F. , Booth C. H. 
Published: April 2011

ABSTRACTWe review resistivity, x-ray-absorption fine-structure (XAFS) and muon spin relaxation (μSR) data which provide clear evidence for localized holes causing polaron distortion and unusual spin dynamics below Tc in “colossal magnetoresistive” (CMR) La1-xCaxMnO3. Resistivity measurements for x=0.33 under an applied field H have shown that ln[ρ(H,T)] α -M, where M is the magnetization. The XAFS data show a similar functional dependence for the polaron distortions on M. The data from these two measurements are interpreted in terms of some fraction of the available holes x remaining localized and some increasing fraction becoming delocalized with increasing M. Finally, this polaron-induced spatial inhomogeneity yields anomalously slow, spatially inhomogeneous spin dynamics below Tc, as shown in the μSR data. These experiments individually probe the charge, lattice and spin degrees of freedom in this CMR system and suggest that the polarons retain some identity even at temperatures significantly below Tc.
The Effect of Radiation Induced Disorder on La0.7Ca0.3MnO3–δ Thin Films
Authors: Stroud R. M. , Browning V. M. , Byers J. M. , Chrisey D. B. , Fuller-Mora W. W. , Grabowski K. S. , Horwitz J. S. , Kim J. , Knies D. L. , Osofsky M. S. 
Published: April 2011

ABSTRACTThe effects of disorder on the transport and magnetic properties of pulsed laser deposited La0.7Ca0.3MnO3 thin films were studied. Ion irradiation with 10 MeV I and 6 MeV Si ions was used to produce controlled levels of defects ranging from 0.006 to 0.024 displacements per atom. The peak resistance temperature of the I-irradiated films decreased from 264K for the undamaged film to OK for the 0.016 dpa film. The magnetic ordering temperature decreased from 270K (undamaged) to 130K (0.011 dpa), and remained nearly constant at 130K for higher damage levels. This demonstrates a decoupling of the magnetic and metal-insulator transitions. A characteristic relationship between the peak resistance temperature and activation energy of resistance with the form Tp = 285(1-Δρ/115)0.13, was observed for all films. This characteristic relationship indicates that the range of resistivity and magnetoresistivity values for observed La0.7Ca0.3MnO3 can be explained in terms of disorder-limited polaron hopping.
Effects of Chromium Ion Implantation on the Magneto-Transport Properties of La0.7Ca0.3MnO3 Thin Films
Authors: De Silva P. S. I. P. N. , Malde N. , Hossain A. K. M. A. , Cohen L. F. , Thomas K. A. , Chater R. , Macmanus-Driscoll J. D. , Tate T. J. , Mathur N. D. , Blamire M. G. , Evetts J. E. 
Published: April 2011

ABSTRACTThin films of colossal magnetoresistance material La0.7Ca0.3MnO3 were implanted with different fluence 200keV Cr ions. Resistivity measurements in zero and applied fields of up to 8T were made in order to determine the effects of the implanted magnetic ions on the magnetoresistance (MR). As the Cr fluence was increased, the resistivity increased and the metal-insulator transition (MI) temperature was suppressed to values below the experimentally accessible temperature range as a result of oxygen loss and the creation of defects. However, for the highest fluence of 5×1015 ions/cm2, a re-entrant metal-insulator type transition was observed. Furthermore a significant improvement in the low field MR was observed for fields less than 500mT. These results are interpreted in terms of substitution of Cr ions onto Mn sites and the creation of a magnetically inhomogeneous material and the influence of oxygen deficiency.
Phase Diagram and Anisotropic Transport Properties of Nd1-xSrxMnO3 Crystals
Authors: Kuwahara H. , Okuda T. , Tomioka Y. , Kimura T. , Asamitsu A. , Tokura Y. 
Published: April 2011

ABSTRACTWe have investigated electronic transport and magnetic properties of perovskite-type Nd1-xSrxMnO3 crystals with change of controlled hole-doping level (0.30≤x≤0.80). The electronic phase diagram of Nd1-xSrxMnO3 was obtained by systematic measurements of magnetization (magnetic structure), resistivity, and lattice parameter. We have also studied the anisotropie transport properties of x=0.50 and 0.55 crystals with different magnetic structures: CE-type antiferromagnetic (AF) structure for x=0.50 and A-type layered AF one for x=0.55. In the case of the x=0.55 crystal, the metallic behavior was observed within the ferromagnetic (F) layers, while along the AF-coupling direction the crystal remains insulating over the whole temperature region. The observed large anisotropy is due to the magnetic as well as orbital-ordering induced confinement of the spin-polarized carriers within the F sheets. The nearly isotropie transport behavior has been confirmed for the CE-type AF charge-ordered state in the x=0.50 crystal.
Stoichiometry and Magnetic Properties of Iron Oxide Films
Authors: Dimitrov D. V. , Hadjipanayis G. C. , Papaefthymiou V. , Simopoulos A. 
Published: April 2011

ABSTRACTThe stoichiometry, structural and magnetic properties, and Mössbauer spectra of reactively sputtered Fe-O films were studied as a function of the O2 partial pressure during the deposition. By increasing the amount of O2 films with the following crystallographic structures and stoichiometry were fabricated; amorphous Fe-O, mixture of Fe and FeO, offstoichiometric single-phase FexO, mixture of FeO and Fe3O4, single-phase Fe3O4, mixture of Fe3O4 and γ-Fe2O3, mixture of Fe3O4 and α-Fe2O3, and single-phase α-Fe2O3. The Verwey transition in Fe3O4 films was observed in the coercivity versus temperature curve and in the thermomagnetic data. FeO and α-Fe2O3 films showed anomalous ferromagnetic-like behavior, in contrast to their anti ferromagnetic nature in bulk. The unusual magnetic properties were attributed to the formation of clusters of tetrahedraly coordinated Fe3+ ions in FeO and to uncompensated surface spins, in α - Fe2O3 films.
Simulation Studies of Polymer Electrolytes for Battery Applications
Authors: Halley J. W. , Nielsen B. 
Published: April 2011

ABSTRACTWe report modeling studies of polyethylene oxide which are carried out with the goal of elucidating the mechanism of ion conduction in the temperature range of interest to battery applications. We review our previous work in which the amorphous regions of the polymer between its glass and melting temperatures is modeled by a molecular dynamics algorithm in which the model system is polymerized from a model monomeric liquid. We describe new work in which the hydrogen centers are added to the model in order to permit comparison with recent neutron work. We compare our simulations of frequency dependent conductivity with experiment and end with a brief discussion of possibilities for improved conductivity which our current understanding suggests.
A COMPOSITE ELECTROLYTE FOR AN SOFC CONSISTING OF A CERIA SHEET AND A ZIRCONIA FILM DEPOSITED BY THE SOL-GEL METHOD
Authors: Chiba Reiichi , Yoshimura Fumikatsu , Yamaki Junichi 
Published: April 2011

ABSTRACTWe investigated a composite electrolyte for solid oxide fuel cells prepared by coating a ceria sheet (Ce0.8Gd0.2O2-d or GDC ) with a scandia alumina doped zirconia (0.850ZrO2-0.110Sc2O3-0.04Al2O3) film by the sol-gel method. The sol-gel film annealed at 1200°C was examined by X-ray diffraction analysis and found to be in a cubic phase at room temperature. The ionic conductivity of this film is comparable to that of bulk sintered at 1620°C. Scanning electron microscope observations revealed that the film forms a good interface with the electrolyte of the ceria sheet, even though the annealing temperature is as low as 1200°C.We fabricated a single cell consisting of a composite electrolyte, a La0.8Sr0.2MnO3 cathode and a Ni-YSZ anode. The composite electrolyte consisted of zirconia film about one micron thick deposited by the sol-gel method and a 0.2 mm thick ceria sheet.A cell operated with moist H2 and O2 gas exhibited an open circuit voltage of 1.00 V at 800°C. This value is much closer to the value of 1.13 V expected from the Nernst equation than the value of 0.76 V for a cell with a ceria sheet but without the sol-gel film.
New Interconnections for Planar Alloy-Separator Sofc Stacks
Authors: Yamazaki Y.-T. , Namikawa T. , Ide T. , Oishi N. , Suzuki O. 
Published: April 2011

ABSTRACTA new design of interconnections between air electrodes and alloy separators in planar stacks is presented. The edges of the air electrodes supporting the electrolyte films are connected, through thin LaCrO3 layers, with the edges of adjacent alloy separators. The electric current in the cell flows radially in the porous thick air electrodes of LSM. The LaCrO3 layers are connected with the alloy separators through nickel felt in the fuel gas atmosphere. By using these interconnections, we can overcome the corrosion problems caused by contacting air electrodes with alloy separators in conventional planar stacks.
Benefits of Rapid Solidification Processing of Modified LaNi5 Alloys by High Pressure Gas Atomization for Battery Applications
Authors: Anderson I. E. , Pecharsky V. K. , Ting J. , Witham C. , Bowman R. C. 
Published: April 2011

ABSTRACTA high pressure gas atomization approach to rapid solidification has been employed to investigate simplified processing of Sn modified LaNi5 powders that can be used for advanced Ni/metal hydride (Ni/MH) batteries. The current industrial practice involves casting large ingots followed by annealing and grinding and utilizes a complex and costly alloy design. This investigation is an attempt to produce powders for battery cathode fabrication that can be used in an as-atomized condition without annealing or grinding. Both Ar and He atomization gas were tried to investigate rapid solidification effects. Sn alloy additions were tested to promote subambient pressure absorption/desorption of hydrogen at ambient temperature. The resulting fine, spherical powders were subject to microstructural analysis, hydrogen gas cycling, and annealing experiments to evaluate suitability for Ni/MH battery applications. The results demonstrate that a brief anneal is required to homogenize the as-solidified microstructure of both Ar and He atomized powders and to achieve a suitable hydrogen absorption behavior. The Sn addition also appears to suppress cracking during hydrogen gas phase cycling in particles smaller than about 25μm. These results suggest that direct powder processing of a LaNi5−xSnx alloy has potential application in rechargeable Ni/MH batteries.
High Performance Vanadium Oxide Thin Film Electrodes for Rechargeable Lithium Batteries
Authors: Zhang Ji-Guang , Liu Ping , Tracy C. Edwin , Benson David K. , Turner John A. 
Published: April 2011

ABSTRACTPlasma Enhanced Chemical Vapor Deposition (PECVD) was used to prepare vanadium oxide thin films as cathodes for rechargeable lithium batteries. The reactants consisted of a high vapor pressure liquid source of vanadium (VOCl3) and hydrogen and oxygen gas. Deposition parameters such as the flow rates of H2, O2 and VOCl3, the substrate temperature and the Rf power were optimized, and high deposition rate of 11 Å/s was obtained. Vanadium oxide films with high discharge capacities of up to 408 mAh/g were prepared. The films also showed a superior cycling stability between 4 and 1.5 V at a C/0.2 rate for more than 4400 cycles. The films were amorphous up to a deposition temperature of 300°C, however, deposition on to substrates with textured surfaces facilitated the formation of crystalline films. We demonstrate that both the vanadium oxide material and the PECVD deposition method are very attractive for constructing thin-film rechargeable lithium batteries with high capacity and long-term cyclic stability.
Magnetic and Transport Properties of Heat-Treated Polyparaphenylene-Based Carbons
Authors: Matthews M. J. , Kobayashi N. , Dresselhaus M. S. , Endo M. , Enoki T. , Karaki T. 
Published: April 2011

ABSRACTElectron spin resonance (ESR), magnetic susceptibility, and transport measurements were recently performed on a set of heat-treated polyparaphenylene (PPP)-based carbon samples, which are of significant interest as novel carbon-based anode electrodes in Li-ion batteries. Attention is focused on the evolution of the carbonaceous structures formed at low heat-treatment temperatures (THT) in the regime of 600° C ≤ THT ≤ 800° C, where percolative transport behavior is observed. At the percolation threshold, the coexistence of two spin centers with peak-to-peak Lorentzian linewidths of ΔHpp(300K) = 0.5 and 5.0 G is observed. The relatively high ratio of hydrogen. carbon (H/C) near is believed to influence the ESR results through an unresolved hyperfine interaction. Curie-Weiss temperaures are found from measurements of [Ipp(ΔHpp)2]–1, where Ipp is the peak-to-peak lineheight, yielding results that are in agreement with static susceptibility, χ(T), measurements. At low THT, PPP-based materials exhibit a large amount of disorder and this is evidenced by the high density of localized spins, Nc, which is obtained from a Curie-Weiss fit to χ(T) assuming a spin quantum number of S = ½. A model explaining the microstructure and high electrochemical doping capacity of PPP samples heat-treated to 700° C can be related to Li-ion battery performance.
A Novel Method for Obtaining a High Performance Carbon Anode for Li-Ion Secondary Batteries
Authors: Takamura T. , Sumiya K. , Nishijima Y. , Suzuki J. , Sekine K. 
Published: April 2011

ABSTRACTEntire surfaces of the pitch-based well graphitized and poorly graphitized carbon fibers were covered with an evaporated metallic film of Au, Ag, Sn, or Zn, whose thickness was varied from 100 to 600 Å. Li dope and undope characteristics as the anode of Li-ion secondary battery were compared for the samples with and without evaporated film. Not only high rate charge/discharge characteristics but cycleability have been realized to be improved remarkably for the sample whose surface was covered with a thin metal film.
Recent Studies of Interfacial Phenomena which Determine the Electrochemical Behavior of Lithium and Lithiated Carbon Anodes with the Emphasis on In Situ Techniques
Authors: Aurbach D. , Schechter A. , Markovsky B. , Cohen Y. , Weissman I. , Moshkovich M. 
Published: April 2011

ABSTRACTThis paper reports on some new results on the application of surface sensitive techniques for the study of the correlation of surface chemistry, morphology and electrochemical behavior of lithium and lithiated graphite as anodes for rechargeable batteries. Surface sensitive FTIR spectroscopy, atomic force microscopy (AFM), electrochemical quartz crystal microbalance (EQCM) were applied to Li and Li-graphite electrodes in a variety of electrolyte solutions of interest, in conjunction with standard electrochemical techniques. The similarity in the surface chemistry developed on Li and lithiated graphite in solutions is demonstrated and discussed. We demonstrate the strong impact of the surface chemistry on the morphology of Li deposition-dissolution processes, and the use of in situ EQCM measurements for the choice of optimal electrolyte solutions for rechargeable batteries with Li metal anodes.
Low Potential Li Insertion in Transition Metal Oxides
Authors: Leroux F. , Nazar L. F. 
Published: April 2011

ABSTRACTLow-potential Li insertion materials comprised of molybdenum oxides (AxMoO3) have been prepared by a “chimie douce” route. Li insertion below 200 mV is associated with dramatic transformation of the structure, leading to a material which displays good cyclability with a high reversible specific capacity of 940 mA/g in the voltage window 3.0–0.005V (volumetric capacity of 4000 mAh/cc), albeit with notable polarization on charge. The structural and compositional changes on discharge to 200 mV have been studied by a combination of XRD, and XAS. The interlayer ions have also been exchanged for Sn, and the electrochemical characteristics of these materials are compared with the alkali derivatives.
Improved Carbon Anode Materials for Lithium-Ion Cells
Authors: Flynn J. , Marsh C. 
Published: April 2011

ABSTRACTSeveral carbon materials have been studied for suitability as anode materials in lithium-ion cells. Carbons that have been included in this evaluation are three grades of commercially available mesophase carbon microbeads (MCMB) 6–28, 10–28 and 25–28, two specially prepared mesophase fibers (Amoco), a foreign mesophase fiber and KS-15 graphite (Lonza). Differences in cycling behavior between the three types of MCMB material are shown. Data of full lithium-ion cells demonstrate the effect that the choice of carbon material has on the cell discharge voltage and capacity. Lithium reference electrode experiments in full cells (3.0–4.0Ah capacity), elucidate the dynamics under several charge/discharge regimes and provide a comparison between the performance of carbon fiber and graphite anode materials. These test results indicate that the fibers can be charged at significantly higher rates than graphite without showing polarization at the anode. Full and half cell data also demonstrates the high coulombic efficiencies of the mesophase materials and first cycle efficiencies as compared to graphite. A comparison of two mesophase materials with different textures in full cells under strenuous cycling conditions shows significant differences in capacity retention. SEM photos of fibers showing the different textures are also presented.
The Effects of Near Surface and Bulk Microstructure on Lithium Intercalation of Disordered, “Hard” Carbons
Authors: Even William R. , Peng Lawrence W. , Yang Nancy , Guidotti Ronald , Headley Thomas 
Published: April 2011

ABSTRACTDisordered carbons were synthesized at 700°C from methacrylonitrile-divinylbenzene precursors. The disorder, even at the free surface, was confirmed with TAM. These powdered carbons were subjected to rapid surface heating by a pulsed infrared laser. While the bulk structure remained essentially unchanged, there was substantial surface reconstruction to a depth of 0.25μm after heating (5.9 W average power at 10Hz, 10 ns pulse width, 1064nm wavelength). The surface ordering appears similar to the bulk microstructure of carbons isothermally annealed at 2,200°C (i.e., turbostratic). Improvements were observed in first cycle irreversible loss, rate capability, and coulombic efficiencies of the reconstructed carbons, relative to the untreated carbon.
Application of Ab Initio Methods to Secondary Lithium Batteries
Authors: Aydinol M K. , Van Der Ven A. , Ceder G. 
Published: April 2011

ABSTRACTAb initio methods have started to be widely used in materials science for the prediction of properties of metals, alloys and compounds. These methods basically require only the atomic numbers of the constituent species. Such methods not only provide us with predictions of some of the properties of the material (even before synthesizing it) but also help us in understanding the phenomena that control those properties.The use of ab initio methods in the field of electrochemistry is, however, quite recent and rare [1–4]. In this study, we demonstrate how ab initio methods can be used to investigate the properties of secondary lithium batteries. Particular examples will be given in predicting average insertion voltages in spinel Li-Mn and Li-Co oxides and in layered LiMO2 (M = Ti, V, Mn, Fe, Co and Al) compounds. Additionally, the stability of these compounds to metal reduction and structural stability of LiCoO2 upon lithium removal is investigated. We find that the oxygen anion plays an active role in the electrochemical intercalation of lithium. The amount of electron transfer to oxygen occurring upon lithium intercalation correlates strongly with the cell voltages. The more electron transfer to oxygen occurs, the higher lithium intercalation potential is obtained.