bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal Structure Analysis in the Dehydrogenation Process of Mg(NH2)2-LiH System
Authors: Noritake Tatsuo , Aoki Masakazu , Towata Shin-ichi , Nakamori Yuko , Orimo Shin-ichi 
Published: April 2011

ABSTRACTMg(NH2)2-LiH system which have the properties of reversible hydrogenation and dehydrogenation is one of the promising candidates for new hydrogen storage materials. For understanding of the reversible reaction mechanism, we investigated the crystal structure changes in 3Mg(NH2)2-12LiH system using the pressure-composition (p-c) isotherm measurement and synchrotron X-ray diffraction. The sample was prepared by the hydrogenation of Mg3N2 + 4Li3N. At the several dehydrogenation stages of the p-c isotherm measurement at temperature 523 K, the sample was taken out and X-ray diffraction measurement was performed. By the amount of desorbed hydrogen, the reaction was expressed as the following formula, Mg(NH2)2 + 4LiH → LixMg(NH2)2-x(NH)x + (4-x)LiH + xH2 (x = 0∼2). The crystal structures of LixMg(NH2)2-x(NH)x, similar to CaF2-type one, formed during the dehydrogenation reaction were determined by Rietveld analysis. As a result, it is considered that the dehydrogenation process might relate to the diffusion of Li+ ion in cation sites of Mg(NH2)2.
Solid Oxide Fuel Cells based on Proton Conducting Electrolytes
Authors: Balachandran U. , Lee Tae H , Ma Beihai , Dorris Stephen E 
Published: April 2011

AbstractWe have fabricated a solid oxide fuel cell (SOFC) using BaCe0.8Y0.2Ox (BCY) proton conductor as the electrolyte. An ≈ 15-μm-thick dense BCY film was prepared on a porous Ni/BCY cermet (i.e., ceramic/metal composite) substrate by a colloidal spray deposition technique. The gas permeable Ni/BCY cermet substrate backed with nickel mesh was used as the anode, and platinum paste backed with platinum mesh served as cathode. The current-voltage characteristics of the BCY-based SOFC were measured in the temperature range 600-800°C using wet air on the cathode side and wet hydrogen on the anode side. The open circuit voltage was close to the theoretical value at all operating temperatures. The power density of the fuel cell was ≈240 and ≈875 mW/cm2 at 600 and 800°C, respectively.
Analysis of Composition and Valence States in Positive Electrode Materials (Fe-Substituted Li2MnO3) for Lithium Ion Batteries by Analytical Transmission Electron Microscopy
Authors: Kikkawa Jun , Akita Tomoki , Tabuchi Mitsuharu , Shikano Masahiro , Tatsumi Kuniaki , Kohyama Masanori 
Published: April 2011

AbstractAnalytical transmission electron microscopy (ATEM) was applied to investigate local variation of composition of transition metals in each particle of Fe-substituted Li2MnO3, which reveals high specific capacity and high voltage as a positive electrode. Crystal lattice images of primary particles were observed by means of high-resolution TEM (HRTEM), where local composition of Fe and Mn was determined by electron energy-loss spectroscopy (EELS). It was found that there exist both manganese (Mn)-rich and iron (Fe)-rich regions in a primary particle, where concentration of Fe and Mn fluctuates irregularly in nanometer scale. The relationship between composition and crystal structure in each local region is discussed.
Li Batteries with Porous Sol-Gel Cathodes
Authors: Dima Antonela , Casalino Maurizio , Della Corte Francesco , Rendina Ivo 
Published: April 2011

AbstractLithium batteries have found a wide range of applications due to their very compact energy packing and effective cost. Theoretically Li-cells can hold up to 5V, however to date no mass-produced rechargeable battery surpasses 4 V. The structure here analyzed consists of: lithium porous cathode, solid electrolyte and silver anode. A spinel LiNi0.4X0.1Mn1.5O4 sol-gel layer was deposited on a porous substrate in order to obtain higher specific surface for single chips. The anode was thermally evaporated Ag. The electrolyte used was a sol-gel hybrid layer containing Li ions. The devices, fabricated on ceramic wafers, displayed high capacities.
Magnetic Studies of Layered Cathode Materials for Lithium Ion Batteries
Authors: Chernova Natasha A. , Ma Miaomiao , Xiao Jie , Whittingham M. Stanley , Cabana Jiménez Jordi , Grey Clare P. 
Published: April 2011

AbstractThe magnetic properties of layered LiNi0.5Mn0.5O2 and NaNi0.5Mn0.5O2 cathode materials are studied using AC susceptibility and DC magnetization techniques in order to elucidate magnetic interactions within transition metal (TM) layers and between them in samples with various TM distributions. In NaNi0.5Mn0.5O2 antiferromagnetic (AF) ordering transition is found at 60 K and a spin-flop transition at high magnetic field. In LiNi0.5Mn0.5O2 obtained by ion exchange from NaNi0.5Mn0.5O2 ferrimagnetic ordering is found at around 100 K. The saturation magnetization and the hysteresis loop size of ion-exchanged compounds vary from sample to sample, which implies that the Ni2+ ions migrate upon ion exchange process. Magnetic properties of high-temperature and ion-exchanged LiNi0.5Mn0.5O2 are compared; magnetic ordering models for all compounds are proposed based on experimental results and Goodenough-Kanamori rules.
A New Lithium Iron Phosphate LiFe2P3O10 Synthesized at 600 °C from Precursor Obtained by Wet Chemistry
Authors: Ait-Salah Atmane , Ramana Chintalapalle V , Gendron François , Morhange Jean-François , Mauger Alain , Selmane Mohamed , Julien Christian M 
Published: April 2011

AbstractWe present the synthesis and characterization of a novel lithium iron polyphosphate LiFe2P3O10 prepared by wet-chemical technique from nitrate precursors. The crystal system is shown to be monoclinic (P21/m space group) and the refined cell parameters are a=4.596 Å, b=8.566 Å, c=9.051 Å and β=97.46°. LiFe2P3O10 has a weak antiferromagnetic ordering below the Néel temperature TN=19 K. Electrochemical measurements carried out at 25 °C in lithium cell with LiPF6-EC-DEC electrolyte show a capacity 70 mAh/g in the voltage range 2.7-3.9 V.
Local Structure and Magnetic Properties of LixFePO4 Glasses
Authors: Jozwiak Pawel , Garbarczyk Jerzy , Gendron François , Mauger Alain , Julien Christian M 
Published: April 2011

AbstractA series of LixFePO4 samples (0≤x≤1) have been synthesized in the vitreous state by fast quenching technique. Characterization methods include XRD, TG, FTIR, magnetic susceptibility and electrical measurements. FTIR studies reveal that in the entire composition range the local structure is identical to the olivine lattice including PO43− oxo-anions linked to FeO6 octahedra. Magnetic susceptibility data show that the antiferromagnetic ordering does not exist so far and the paramagnetic behaviour follows the Curie-Weiss law above 30 K. Both the Curie parameter and the Weiss temperature suggest a strong weakness of the superexchange interactions that are consistent with the analysis of infrared spectra. Electrical conductivity shows an activated conduction mechanism with Ea=0.67 eV.
Preparation and Characterization of ALD TiN Thin Films on Lithium Titanate Spinel (Li4Ti5O12) for Lithium Ion Battery Applications
Authors: Snyder Mark Q. , Trebukhova Svetlana , Ravdel Boris , Wheeler M. Clayton , DiCarlo Joseph , Tripp Carl P. , DeSisto William J. 
Published: April 2011

AbstractLithium titanate spinel (Li4Ti5O12, or LTS) has received an increasing level of attention as a nanopowder lithium-ion battery anode. Nanopowder electrodes may provide a higher energy density than currently available. Furthermore, the surface of the spinel nanopowder has been studied in air, under vacuum, and at varying temperatures with diffuse reflectance infrared Fourier transform spectroscopy revealing surface hydroxyls, carbonates and water. Applying a TiN thin film, a film that is both conducting and chemically inert to harmful reactions with the solvent/electrolyte, by atomic layer deposition (ALD) may enhance battery cycle life. A 200-layer film was deposited at 500 °C. We have characterized the influence of a TiN thin film on Li-ion battery performance. Total nitrogen content and transmission electron microscopy were used to verify the presence of nitrogen and formation of a thin film, respectively, on LTS. Modifying the powder with an ALD thin film coating produced an anode material with a voltage profile that demonstrated longer charge maintenance with shorter transient periods. It also held a more consistent charge capacity over varying discharge rates in coin cell testing than unmodified LTS.
A Survey of Diverse Approximations for Microstructural Characterization using Powder Diffraction Data: β-Ni(OH)2, a Case Study
Authors: Casas-Cabanas Monste , Rodriguez-Carvajal Juan , Oro-Sole Judith , Palacin M. Rosa 
Published: April 2011

AbstractThe microstructural features of diverse samples are studied by powder X-ray diffraction using different methods for the analysis of the diffraction peak broadening. The results obtained are thoroughly analyzed taking into account the assumptions and simplifications done in each of the chosen methods (Scherrer, Stokes and Wilson, Williamson-Hall and Rietveld refinement) and direct observation of the studied specimens by transmission electron microscopy is used in order to contrast the results obtained. Classic simple methods that consider only size effects (Scherrer, Stokes and Wilson) or the combined effects of size and strains (Williamson-Hall) provide a rapid overview of the origins of line-broadening but the most reliable results are obtained when the whole diffraction pattern is taken into account (Rietveld refinement).
Intermediate Phases in LixFePO4
Authors: Yamada Atsuo , Nishimura Shinichi , Koizumi Hiroshi , Kanno Ryoji , Seki Shiro , Kobayashi Yo , Miyashiro Hajime , Dodd Joanna , Yazami Rachid , Fultz Brent 
Published: April 2011

AbstractRietveld analysis for the time of flight powder neutron diffraction profile for LiFePO4 at room temperature was performed. Refined tensor elements of the unisotropic thermal factor under the elliptic approximation showed the principal axis of the lithium vibration is toward the face shared vacant tetrahedral space and is consistent with the theoretical prediction; lithium ions diffuse along curved one-dementional chain along b-axis. Impact of temperature on the phase diagram of LixFePO4 with > 200nm particle size was slight under the unmixing line around 200 C. While the reduction in particle size down to <100 nm seems to have significant effect to the room temperature miscibility gap. The thermodynamic concepts for the extended solution in smaller particles are discussed, followed by a demonstration of very high rate capability observed for the small spherical particles < 80 nm.
Demonstration of a Novel Alkaline Battery Cathode Material: Periodate Salts
Authors: Licht Stuart , Yu Xingwen 
Published: April 2011

ABSTRACTAn unusual solubility domain for KIO4 in KOH solution is observed, which is consistent with a potential use of periodate as a cathode for alkaline batteries. With increasing alkalinity, the solubility of KIO4 first increases, then drops from 2.9 M to < 10−4 M with increase from 6 to 10 M KOH. The unusual rapid transition from high to low solubility with increasing KOH is attributed to the formation of insoluble periodate complex. Accompanying the favorable low solubility in concentrated KOH is a high degree of cathodic electroactivity in accord with two electron storage: IO4− ⊒ IO3−. Low cathode salt solubility minimizes interference with the anode. Zn anode alkaline batteries are studied with KIO4 and NaIO4 cathodes, have a potential of 1.4-1.5 V and discharge to over 95% of the intrinsic 2e− charge capacity. The cathode also exhibits good quasi reversibility (rechargeability) with an alkaline metal hydride anode.
Comparison of Techniques for Measuring Recombination Lifetime in Photovoltaic Materials: Trapping Effects
Authors: Ahrenkiel Richard K , Johnston Steven W. , Metzger Wyatt K 
Published: April 2011

ABSTRACTHere we will compare four techniques that are commonly used for diagnosis of the lifetime of photovoltaic materials. The strengths and weaknesses of these techniques will be shown and discussed.
Optimization of Textured Photonic Crystal Backside Reflector for Si Thin Film Solar Cells
Authors: Zeng Lirong , Bermel Peter , Yi Yasha , Feng Ning-ning , Alamariu Bernard A. , Hong Ching-yin , Duan Xiaoman , Joannopoulos John , Kimerling Lionel C. 
Published: April 2011

ABSTRACTA new backside reflector, textured photonic crystal, is introduced into Si thin film solar cells. Scattering matrix method is used to systematically optimize all the parameters of the two components of the backside reflector, grating and distributed Bragg reflector, to achieve the highest power conversion efficiency for a given solar cell thickness. Experimentally, Si-on-insulator solar cells are being fabricated to verify the tremendous efficiency enhancement and optimal design. It is found that while the optimal period and etch depth of the grating, the Bragg wavelength of the distributed Bragg reflector, as well as the antireflection coating thickness all decrease as the cell becomes thinner, the optimum duty cycle of the grating remains almost constant at 0.5. For a 2 μm thick cell, the relative efficiency enhancement can be as high as 52% using the optimized design.
Solar Cells Using Solution-derived Oxide Films as Photoelectrodes
Authors: Gao Yanfeng , Nagai Masayuki 
Published: April 2011

ABSTRACTThis paper reports the development of morphology-tuned TiO2/ZnO films and their application to the electrode in dye-sensitized solar cells. Amorphous TiO2 precursor films with different morphologies can be synthesized under different processing conditions by our previously developed peroxotitanate-complex deposition process, which employs a supersaturated peroxotitanate aqueous solution. The ZnO nanowire aligns were grown by a two-step method, in which well oriented arrays of ZnO nanowires were prepared on a pre-prepared ZnO seed layer. The cell performance using the prepared TiO2/ZnO films shows the possibility to integrate these films into solar cells. However, the crystallization and morphology should be further optimized to improve the conversion efficiency to be a competitive level.
Photocatalytic Hydrogen Evolution over Tantalate Photocatalysts
Authors: Jitputti Jaturong , Pavasupree Sorapong , Suzuki Yoshikazu , Yoshikawa Susumu 
Published: April 2011

ABSTRACTTantalate and titanate photocatalysts were prepared by solid-state reaction at 1273 K using various ratios of SrCO3, Ta2O5, and TiO2 as starting materials. The prepared solid photocatalysts were characterized using XRD and SEM analysis. These prepared tantalate and titanate photocatalysts showed high photocatalytic H2 evolution activity by water splitting without co-catalyst loading. The highest H2 evolution rate of prepared photocatalysts was found to be 138 μmolh−1 with the starting materials ratio of 2/0.5/1.5 (Sr/Ta/Ti; mol). Furthermore, this photocatalyst showed photocatalytic activity for H2 evolution from distilled water.
Crystalline Titania Nanoplatelet Templated by Block Copolymer of PMMA-b-PEO and its Photophysical Properties
Authors: Cheng Yajun , Memesa Mine , Nett Sebastian , Gutmann Jochen Stefan 
Published: April 2011

ABSTRACTA Titanium dioxide ultrathin film composed of nanoplatelet structures was prepared and characterized with AFM, SEM, and GISAXS measurement, whose photophysical properties are also studied.
Spin Density in Thin Film Silicon Before and After Electron Bombardment
Authors: Astakhov Oleksandr , Carius Reinhard , Petrusenko Yuri , Borysenko Valeriy , Barankov Dmitry , Finger Friedhelm 
Published: April 2011

AbstractThe defect density in thin film silicon was increased using low temperature 2MeV electron irradiation up to a factor of 1000. More than 30 samples of different structure from highly crystalline to amorphous were prepared with PECVD and irradiated to study the dynamics of defect accumulation and role of the material structure in this process.
Light Soaking and Thermal Annealing Effects on the Micro-Electrical Properties of Amorphous and Nanocrystalline Mixed-phase Silicon Solar Cells
Authors: Jiang Chunsheng , Yan B. , Moutinho H. R. , Al-Jassim M. M. , Yang J. , Guha S. 
Published: April 2011

AbstractWe report on the measurement of local current flow in hydrogenated amorphous and nanocrystalline mixed-phase n-i-p silicon solar cells in the initial, light-soaked, and annealed states using conductive atomic force microscopy (C-AFM). The C-AFM measurement shows that the nanometer-size grains aggregate, and the local current densities in the nanocrystalline aggregation areas decreased significantly after light soaking and recovered to values similar to the initial state after annealing at a high temperature in a vacuum. This result supports the model of two parallel-connected diodes for explaining the light-induced open-circuit voltage increase in the mixed-phase solar cells.
High Open-Circuit Voltage in Silicon Heterojunction Solar Cells
Authors: Wang Qi , Page Matt R. , Iwancizko Eugene , Xu Yueqin , Roybal Lorenzo , Bauer Russell , Levi Dean , Yan Yanfa , Wang Tihu , Branz Howard M. 
Published: April 2011

AbstractHigh open-circuit voltage (Voc) silicon heterojunction (SHJ) solar cells are fabricated in double-heterojunction a-Si:H/c-Si/a-Si:H structures using low temperature (<225°C) hydrogenated amorphous silicon (a-Si:H) contacts deposited by hot-wire chemical vapor deposition (HWCVD). On p-type c-Si float-zone wafers, we used an amorphous n/i contact to the top surface and an i/p contact to the back surface to obtain a Voc of 667 mV in a 1 cm2 cell with an efficiency of 18.2%. This is the best reported p-type SHJ voltage. In our labs, it improves over the 652 mV cell obtained with a front amorphous n/i heterojunction emitter and a high-temperature alloyed Al back-surface-field contact. On n-type c-Si float-zone wafers, we used an a Si:H (p/i) front emitter and an a-Si:H (i/n) back contact to achieve a Voc of 691 mV on 1 cm2 cell. Though not as high as the 730 mV reported by Sanyo on n-wafers, this is the highest reported Voc for SHJ c-Si cells processed by the HWCVD technique. We found that effective c-Si surface cleaning and a double-heterojunction are keys to obtaining high Voc. Transmission electron microscopy reveals that high Voc cells require an abrupt interface from c-Si to a-Si:H. If the transition from the base wafer to the a-Si:H incorporates either microcrystalline or epitaxial Si at c Si interface, a low Voc will result. Lifetime measurement shows that the back-surface-recombination velocity (BSRV) can be reduced to ~15 cm/s through a-Si:H passivation. Amorphous silicon heterojunction layers on crystalline wafers thus combine low-surface recombination velocity with excellent carrier extraction.
Low Temperature Epitaxy of n-Doped Silicon Thin Films Using Plasma Enhanced Chemical Vapor Deposition
Authors: Farrokh Baroughi Mahdi , El-Gohary Hassan G. , Cheng Cherry Y. , Sivoththaman Siva 
Published: April 2011

AbstractHighly conductive epiraxial silicon thin films, with conductivities more than 680 ¥Ø-1cm-1, were obtained using plasma enhanced chemical vapor deposition (PECVD) technique at 300¢ªC. The effect of hydrogen in growth of low temperature extrinsic Si thin films was studied using conductivity, Hall, and Raman measurements, and it was shown that epitaxial growth was possible at hydrogen dilution (HD) ratios more than 85%. The epitaxial growth of the extrinsic Si thin films at high hydrogen dilution regime was confirmed by high resolution transmission electron microscopy (HRTEM).
Boron Doping Effects in Microcrystalline Silicon
Authors: Beyer Wolfhard , Niessen Lars , Pennartz Frank 
Published: April 2011

AbstractConditions leading to high conductivities (up to 300 S/cm) in chlorosilane-based boron-doped microcrystalline Si:Cl:H films are investigated. It is found that the high conductivity originates primarily from the growth of highly crystalline material with a high concentration of boron. Furthermore, these films grow with relatively low chlorine and hydrogen concentrations of a few percent and, according to effusion measurements of hydrogen and implanted helium, in a relatively compact structure. At a boron doping level of 1%, admixture of 10% silane to the tetrachlorosilane results in the growth of amorphous material of low conductivity while for admixture of up to 90% of silicontetrafluoride, microcrystalline Si films with high conductivities can be grown.
Optical Readout in Pinpi'n and Pini'p Imagers: A Comparison
Authors: Louro P. , Vieira M. , Vygranenko Y. , Fernandes M. , Garção A. 
Published: April 2011

AbstractOptimized a-SiC:H multilayer devices based on two different tandem configurations (TCO/pinpi'n/TCO and TCO/pini'p/TCO) are compared and tested for proper image recognition and color separation process using an optical readout technique. In both configurations the doped layers are based on a-SiC:H to increase image resolution and to prevent image blurring. To profit from the light filtering properties of the active absorbers, the intrinsic layer of the front diode (i layer) is based on a-SiC:H and the back one (i'layer) on a-Si:H.The effect of the applied voltage on the color selectivity is discussed. Results show that the relative spectral response curves demonstrate rather good separation between the red, green and blue basic colors. Combining the information obtained under positive and negative applied bias a colour image is acquired, using the same optical technique either in pinpi'n or in the pini'p configuration, without colour filters or pixel architecture.
High Rate Deposition of Amorphous Silicon Based Solar Cells using Modified Very High Frequency Glow Discharge
Authors: Yue Guozhen , Yan Baojie , Yang Jeffrey , Guha Subhendu 
Published: April 2011

AbstractWe report our recent progress on high rate deposition of hydrogenated amorphous silicon (a-Si:H) and silicon germanium (a-SiGe:H) based n-i-p solar cells. The intrinsic a-Si:H and a-SiGe:H layers were deposited using modified very high frequency (MVHF) glow discharge. We found that both the initial cell performance and stability of the MVHF a-Si:H single-junction cells are independent of the deposition rate up to 15 Å/s. The average initial and stable active-area cell efficiencies of 10.0% and 8.5%, respectively, were obtained for the cells on textured Ag/ZnO coated stainless steel substrates. a-SiGe:H single-junction cells were also optimized at a rate of ~10 Å/s. The cell performance is similar to those made using conventional radio frequency technique at 3 Å/s. By combining the optimized component cells made at 10 Å/s, an a-Si:H/a-SiGe:H double-junction solar cell with an initial active-area efficiency of 11.7% was achieved.
Modeling the Laser Scanned Photodiode S-shaped J-V Characteristic.
Authors: Fernandes Miguel , Vieira Manuela , Martins Rodrigo 
Published: April 2011

AbstractThe devices analyzed in this work present an S-shape J-V characteristic when illuminated. By changing the light flux a non linear dependence of the photocurrent with illumination is observed. Thus a low intensity light beam can be used to probe the local illumination conditions, since a relationship exists between the probe beam photocurrent and the steady state illumination. Numerical simulation studies showed that the origin of this S-shape lies in a reduced electric field across the intrinsic region, which causes an increase in the recombination losses. Based on this, we present a model for the device consisting of a modulated barrier recombination junction in addition to the p-i-n junction. The simulated results are in good agreement with the experimental data.Using the presented model a good estimative of the LSP signal under different illumination conditions can be obtained, thus simplifying the development of applications using the LSP as an image sensor, with advantages over the existing imaging systems in the large area sensor fields with the low cost associated to the amorphous silicon technology.