In this paper, we report on the preparation of synthetic FeS2 and CoS2 using a relatively inexpensive aqueous process. This avoids the material and handling difficulties associated with a high-temperature approach. An aqueous approach also allows ready scale-up to a pilot-plant size facility. The FeS2 and CoS2 were characterized with respect to their physical and chemical properties. The synthetic disulfides were incorporated into catholyte mixes for testing in single cells and batteries over a range of temperatures. The results of these tests are presented and compared to the performance of natural FeS2 (pyrite) and a commercial source of CoS2.

A charge density study of boron carbide B12C3 single crystals at different temperatures allows a quantitative description of the electron density responsible for chemical bonding. These results, based on direct observations, are compared to previous models of bonding. This description points out that structural features are more complex than suggested by simple qualitative models. The effects of chemical substitution, the characteristics of the interatomic bonding, the charge transfer and the bond strength are discussed and compared to the information obtained from previous conventional refinements and ab-initio calculations in disordered B12C3.

A number of Sn/C composites were prepared for evaluation as anode materials for Li-ion cells. In one case, samples were prepared by incorporation of Sn species into organic precursors that were then pyrolyzed under an Ar/H2 cover gas to prepare the Sn/C composites. They were also prepared by decoration of various types of carbon with nanoparticles of Sn by electroless deposition using hydrazine. The carbons examined included a disordered carbon prepared in house from poly(methacrylonitrile), a mesocarbon microbead (MCMB) carbon, and a platelet graphite. The Sn/C composites were examined by x-ray diffraction (XRD) and scanning electron microscopy (SEM) and were also analyzed for Sn content. They were then tested as anodes in three-electrode cells against Li metal using 1M LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC) solution. The best overall electrochemical performance was obtained with a Sn/C composite made by electroless deposition of 10% Sn onto platelet graphite.

Chemical bath deposition of thin films of antimony selenide from aqueous solutions containing complexes of antimony with citrate, tartrate and thiosulfate as ligands and sodium selenosulfate as source of selenide is reported. The films obtained appear amorphous in the as-prepared form and become crystalline upon annealing at 300°C. The X-ray Diffraction (XRD) patterns of the annealed films show peaks attributable to Sb2Se3 and Sb2O3. Electron microprobe analyses have shown that the atomic ratio of Se/Sb is less than 1.5 in these films. The films are photoconductive and exhibit a high resistivity in the dark. Both direct (1.4 eV) and indirect (1.3-1.5 eV) band gaps are observed for the films.

Typically, useful thermoelectrics are small-gap semiconductors. Mo3Sb7 would be an interesting candidate, if it were not metallic. Electronic structure calculations reveal that metallic Mo3Sb7 can be made semiconducting by heavy doping, e.g., by replacing Sb in part with Te. We succeeded in the preparation of semiconducting Mo3Sb5-xTe2+x with enhanced thermoelectric properties. Furthermore, we incorporated small M atoms into the cubic Sb/Te cage in an attempt to create the rattling effect as found in the filled skutterudites that have attracted wide interest for their outstanding thermoelectric properties.

This paper deals with: i) the growth of LiMn2O4 crystals by electrocrystallisation; ii) the response of these crystals in lithium cells; and iii) a method to follow their structural and morphological changes while working as electrodes. The defects present in LiMn2O4 crystals are determined after refining the occupation at every site of the spinel structure by single-crystal Xray diffraction analyses, which lead to define two possible paths for the process of Li deinsertion-insertion. It is shown how the crystals studied follow one of these paths during cycling of the battery by virtue of a dynamic mechanism consisting in Mn migrations cooperatively induced by Li insertion and extraction.

ZnO with hexagonal wurzite structure is a wide band gap n-type semiconductor. ZnO films can be prepared to obtain high transparency in the visible range, low resistivity, chemical stability and stability in hydrogen plasma including many foreign materials such as Al, In. In this work, we prepared ZnO:Al thin film by Facing Targets Sputtering system with Zn metal target and ZnO:Al(Al2O3 2wt%, 4wt%) ceramic target at total working gas pressure 1mTorr, substrate temperature R.T.. We evaluated the crystallographic, electrical and optical characteristics of the ZnO:Al films.

Aluminum doped ZnO films are deposited on glass substrates at a temperature of 200°C by expanding thermal plasma CVD. Surface texture, morphology and crystal structure have been studied by AFM, SEM and XRD. A rough surface texture, which is essential for application as front electrode in thin film solar cells, is obtained during deposition. The addition of aluminum as a dopant results in distinct differences in film morphology, a transition from large, rounded crystallites to a more pyramid-like structure is observed. The structure of films is hexagonal with a preferred crystal orientation in the faces (002) and (004), indicating that films are oriented with their c-axes perpendicular to the substrate plane. In addition, spectroscopic ellipsometry is used to evaluate optical and electronic film properties. The presence of aluminum donors in doped films is confirmed by a shift in the ZnO band gap energy from 3.32 to 3.65 eV. In combination with reflection and transmission measurements in the visible and NIR ranges, film resistivities have been obtained from the free-carrier absorption. These results are consistent with direct measurements. Resistivities as low as 6.0 10-4 Ωcm have been obtained.

Studies related to the effects of grain size (30nm – 5.0μm) on the electrical conductivity of undoped CeO2 and Ce0.90Gd0.10O1.95 were performed. A series of impedance spectra as a function of temperature and grain size were analyzed. It was found that the ratio of the grain boundary resistance to the total resistance became lower with decreasing grain size, increasing temperature or increasing Gd content. For the case of Gd doped CeO2, the source of the grain boundary resistance may be due to the trapping of oxygen ions in the grain boundary area.

The ternary chalcopyrite semiconductors I-III-VI are currently used for photovoltaic solar cell applications. In this study, AgIn5S8 thin films were prepared from a series of single-source bimetalorganic precursors, e.g. [(PPh3)2AgIn(SC{O}R)4] (R = alkyl) by aerosol assisted chemical vapour deposition (AA-CVD). The compounds can be used as single-source precursors for the deposition of ternary compounds (I-III-VI) by one-pot reaction using CVD process and they are found to be air stable, which is favourable in comparison with metal alkyl compounds, which are found to be pyrophoroic. The optimum growth temperature for the preparation of these films on glass and Si(100) substrates, was found to be above 350°C in terms of crystallinity, although deposition occurred at low temperatures. The films have been investigated using XRD, SEM and EDS. SEM analysis shows that all films are microcrystalline but have different morphologies depending on the growth temperatures. XRD results show evidence of the crystalline nature of these films. The results of this comprehensive study are presented and discussed.

A remarkable reduction in reaction temperature was found for the hydrogenation of Li metal in Li-C mixture. H2 uptake started at 50°C, became vigorous at 150°C and slowed down at temperatures above 200°C. In-situ XRD characterizations revealed that Li-C intercalation compounds such as LiC6 and LiC12 existed in the Li-C samples, and LiH formed after the hydrogenation taking place. Increasing the carbon content in the Li-C mixture, from Li/C = 10:1 to 5:1 and then to 2:1, would enhance the reactivity of hydrogenation accordingly. Carbon nanotubes, with smaller size and larger specific area, showed even greater enhancement of the hydrogenation of lithium metal than graphite. The mechanism for the low temperature hydrogenation of Li-C samples was studied and discussed.

CuxGaySe2 MOCVD and PVD grown films were structurally and optically characterized by Raman, Micro-Raman and photoluminescence spectroscopy. Defect related photoluminescence excitation with wavelengths varying across the material band gap reveals: a) in Cu-rich CuGaSe2 films, three band edge splitting due to the spin-orbit interaction and the crystal field, and donor-acceptor pair recombination between a shallow donor and two different acceptor levels, and b) in Ga-rich CuGaSe2 films, donor-acceptor pair transitions between quasi-continua of donor and acceptor levels related to potential fluctuations. Raman spectra of CuxGaySe2films, excited by laser light near and below the material band gap, show intense modes at 197cm-1, 187cm-1, and 277cm-1, which can be used as indicators of crystallinity and Ga-content of the films. Polarization- and angular- dependent micro-Raman spectra of MOCVD CuGaSe2 indicate that CuxSey-crystallites, dispersed on the surface of Cu-rich films, are grown oriented with their c-axis perpendicular to the film surface.

Thin films of CdS and CdSe have been deposited on glass substrates by low pressure metal-organic chemical vapour deposition (LP-MOCVD) using Cd[(EPiPr2)2N]2 (E = S, Se) as single-source precursors. These air-stable precursors are volatile, making them suitable for the deposition of thin films. As-deposited films were crystalline metal chalcogenides, as confirmed by X-ray powder diffraction (XRD), and their morphologies were studied by scanning electron microscopy (SEM).

The P3 Micro Heat Engine relies on a thin film PZT based transducer to convert mechanical energy into usable electrical power. In an effort to increase process yield for these were used on sputtered Ti/Pt bottom electrodes to compare roughness, grain size, and diffusion for annealing temperatures between 550 and 700 °C. For an optimized bottom electrode, process yield for various sized top electrodes were then studied for PZT thickness between 0.54 and 1.62 for reducing stress concentrations. Two PZT etching geometries on 2.3 μm thick Si/SiO2 membranes, with 1.5-3.5 mm side-lengths, were examined and one was used to increase the strain at failure by at least 40%. Integrating improvements in process yield and strain at failure, single PZT based MEMS devices capable of generating power of up to 1 mW and in excess of 2 volts have been demonstrated operating at frequencies between 300 and 1,100 Hz.

Several iron phosphates were synthesized by solution-based techniques and tested as cathodes in non aqueous lithium cells. The addition of phosphate ions to a solution of iron (II) produced crystalline Fe3(PO4)2. This material is easily oxidized by air to form an amorphous phase that is able to reversibly intercalate lithium. The amorphous compound was identified to be a mixture of FePO4 and Fe2O3. A new synthetic route was developed to prepare pure amorphous FePO4. Amorphous LiFePO4 was obtained by chemical lithiation of FePO4. The material was heated at 500°C under reducing atmosphere to obtain nano-crystalline LiFePO4. This latter material showed excellent electrochemical performance when used as cathode of lithium cells.

Recently discovered borates, LiMBO3 (M=Fe, Mn), share similarities with LiFe(Mn)PO4. They are polyanion structures, contain extractable lithium and suffer from low electronic conductivity. They are attractive to replace expensive, less abundant redox metals in current use in cathodes with environmentally friendly iron or manganese. Phosphate or borate groups adjacent to the redox active metal increase the voltage of the redox couple through an inductive effect. The LiFeBO3 discharge curve shows a pseudo-plateau around 2.6 V for the Fe(II) / Fe(III) couple. This study brings to bear techniques to improve electrode conductivity to produce LiMBO3 composite electrodes thus allowing access to some of the high, theoretical specific capacity. At low current, up to 70 percent of lithium could be extracted from LiFeBO3 that was prepared in the presence of high surface area, highly electrically conductive carbon black. Attempts to improve the cathode properties of LiMnBO3 were less successful.

β-FeSi2 was firstly formed by implanting Si wafers with Fe ions at 50 kV to a dose of 5×1017/cm2in a strong current Metal Vapor Vacuum Arc (MEVVA) implanter. Secondly, Ti implantation was performed on these Fe as-implanted samples. The Fe + Ti implanted samples were furnace annealed in vacuum at temperatures ranging from 650 to 975°C. The XRD patterns of the annealed samples correspond to β-FeSi2 structure (namely β-Fe(Ti)Si2). When annealing was done above 1050°C, the β-Fe(Ti)Si2 transformed into α-Fe(Ti)Si2. This implies that introducing Ti stabilizes the β-FeSi2 phase. Resistance measurements were also performed.

Results for solar cells with high specific power (W/kg) using amorphous silicon alloy technology are reported. Currently available roll-to-roll production technology capable of high volume has been used to form cells on thinned stainless steel with high specific power. Results of cells on thinned stainless steel formed in batch mode in research and development (R&D) machines are also presented. Cells on polyimide in the early R&D stage have also been formed and are described. An analysis of cell component material and dimension changes to increase specific power shows that specific power ∼2000 W/kg is possible as a long-term goal. Cells with specific power ranging from 300 to 400 W/kg for production cells with 8.5 % beginning of life AM0 efficiency to over 1200 W/kg for R&D cells on polyimide substrates are presented.

Significant effort to develop a robust rechargeable battery has been put in the past two decades. The efforts were mainly focused on developing rechargeable battery systems which exhibit high capacity, long cycle life and high discharge rate capabilities. LiMn2O4 based cathodes have been researched extensively as they are not only economical but also environmentally desirable. Research includes composition and doping variation, formation of novel phases and microstructural tailoring, but none of the material modifications have successfully satisfied all the above mentioned performance criteria. In this paper we show a correlation between processing parameters, microstructure and electrochemical performance of Li-Mn-O cathode films. In addition we discuss the formation of metastable oxygen-rich lithium manganospinels, using a unique ultraviolet assisted deposition process. These defective films exhibit high capacity (> 230 mAh/gm), long cycle life (less than 0.05 % capacity loss per cycle for the first 700 cycles), and high discharge rates (> 25 C for 25 % capacity loss). The long cycle life and high capacity was attributed to the ability to cycle the Mn+ valence to less than 3.5 without onset of Jahn-Teller structural transformation, while the high discharge rate was attributed to the extremely high diffusivity of Li+ in the defective Li1-δMn2-2δO4 phase.

Bismuth sulfide (Bi2S3), a direct band gap material with Eg ñ 1.3 eV, attracts high interest in thermoelectric investigations. In this work, nanometer-sized bismuth sulfide with unique morphology has been successfully prepared by a precipitation between bismuth 2-ethylhexanoate and thioacetamide in high-temperature organic solution with presence of proper capping/ stabilizing agents. By employing this technique, we are able to produce nanobeads of bismuth sulfide with an aspect ratio of ∼ 5, typically ~10 nm wide and ∼50 nm long according to the TEM observation. Characterization of XRD and TEM/HRTEM reveals that the as-prepared particles exist in single orthorhombic phase and possess high crystallinity. The composite ratio between Bi and S can be adjusted by varying the ratio between two precursors and was determined by using EDS (TEM) technique. Thermoelectric properties of these bismuth sulfide nanobeads were also investigated and will be discussed comparatively with those from commercial bulk materials.