In-situ XAS studies have been carried out on PEM fuel cells in methanol and hydrogen operation. This has become possible due to a recently developed PEM fuel cell (single cell) equipped with inherent carbon fibre windows to allow x-ray studies in transmission geometry. The set-up chosen allows the in-situ monitoring of the structural changes of the Pt-Ru catalyst, utilised as electrode active material, during cell operation. The analysis of the white line intensities, edge shifts of the Pt-Lш edge and the XAFS signal, which was modelled for the first co-ordination shell around Platinum, exhibited no significant changes during operation in terms of the first neighbouring shell. Nevertheless, the white line intensity decreased comparing the ex-situ to in-situ measurements. From the latter, can be concluded that the catalyst is reduced during operation and further, the redox behaviour of the catalyst does not change the local environment of the Pt-centres in the first co-ordination shell to a measurable extend.

Tracer diffusion experiments were carried out in synthetic air at 1573 K in SrTiO3(100) and (110) single crystals, which were either undoped or doped with up to 1 at.% La, respectively. Tracer sources of 139La and 142Nd were applied by ion implantation. The resulting depth profiles were measured by SIMS. The reconstruction of the surface was monitored ex-situ using microscopic and spectroscopic methods including SEM, EPMA, and AFM. The measured tracer diffusivities show no dependency on orientation. The tracer diffusion takes place via cation vacancies. Under oxidizing conditions the dopant is compensated by Sr vacancies. Hence the diffusion is increasing strongly with La concentration. The observed time dependency of the diffusivities may be related to a space charge layer postulated by the current defect chemistry model for donor doped SrTiO3. At high dopant concentrations annealing leads to segregation of bulk La to the surface. La is not significantly incorporated into the secondary crystallites at the surface which consist almost entirely of Sr and O.

Progress has been made in designing an anode electrode that can tolerate CO levels of several thousand ppm which are a typical output of a fuel processor consisting of a reformer and water-gas-shift unit only. The combination of a PtMo catalyst that is capable of electrochemically oxidising CO and a PtRu catalyst that can tolerate high levels of CO2 arranged in a bilayer configuration, has been shown to tolerate 2000 ppm CO in H2 with a relatively small loss in fuel cell performance. Further improvements in the ability to tolerate higher levels of CO with lower performance losses are expected due to improved PtMo catalyst design.

The performance of the langasite-based crystal microbalance is limited due to reductions in its resistivity at high temperatures and reduced oxygen partial pressures. In this work, we utilize a recently developed defect model to predict the dependence of the ionic and electronic contributions to the total conductivity of langasite on temperature, oxygen partial pressure and acceptor and donor dopants. These results are used to select the type and concentrations of dopants expected to provide extended operating conditions for langasite-based gas sensors and crystal microbalances.

Through the use of nanostructures and nanocomposites, the electrochemical activity of metal fluoride materials was opened as potential candidates as next generation high energy density positive electrodes for Li batteries. This class of materials, utilizing FeF3 as an example, is shown to exhibit good reversible behavior of approximately 200 mAh/g in the 3V region. The specific capacity is extended to 600 mAh/g when the discharge is extended to take into account the additional specific capacity associated with a 2V plateau. Through the use of XRD, SAED and high resolution TEM, the 2V reaction mechanism was associated to a reversible metal fluoride conversion mechanism. It is shown that LiF + Fe nanocomposite can be utilized as initial components in order to make the technology suitable for Li-ion applications. Although exhibiting relatively poor rate capabilities at this initial stage, reversible conversion metal fluorides enable for the first time the utilization of all the redox states of the constituent metal in a reversible manner in the positive electrode. This translates to 4X the specific capacity and double the energy density of today's state of the art LiCoO2.

In this work we have shown the influence of the microstructure and nanochemistry on the transport properties of Y2O3-(9mol%) stabilized zirconia and Gd2O3 (10 mol%)-doped ceria. Zirconia (YSZ) samples show transport properties (DO, σgb) which increase with the grain size, while they decrease in ceria (GSC). This difference was attributed to the presence of glassy grain boundary precipitates in YSZ. On the other hand, it was shown that kinetic demixing processes during cooling, at the end of sintering, play an important role on the grain boundary properties of these oxides.

X-ray absorption spectroscopy (XAS) measurements were performed to thoroughly understand lithium insertion mechanism in Li1.2V3O8. The evolution of the absorption pre-edge and edge corresponding to the local environment of the vanadium in the bulk has been examined by ex-si tu XAS measurement at the vanadium K edge, during the first discharge-charge cycle. The results show a regular and reversible evolution of the pre-edge intensity, the edge position and the vanadium environment toward nearly perfect VO6 octahedra.

The isothermal conductivity of natural stilbite single crystals depends on water content, polar organic molecule concentration and charge compensating cation species. The observed interaction processes are almost completely adsorptive at temperatures below 110°C; catalytic oxidation of the organic molecules is taking place at much higher temperatures, where zeolitic water is almost completely desorbed. A schematic model describing the observed conductivity modifications is developed.

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.

Aurivillius phases of the type Bi2Sr2Nb2TiO12 and Bi1.6Pb0.4Sr2Nb2Ti1-xAlxO12 (0.0 ≤ × ≤ 0.8) were synthesized by the polymerized complex method involving an organometallic precursor. The effect of raising the pH of the solution was investigated through the addition of ammonium hydroxide. Infrared spectroscopy was taken at various points in the reaction to generate a mechanism. The IR data showed the formation of an ester as well as an amide with the addition of ammonium hydroxide. Pure Bi2Sr2Nb2TiO12 was formed after heat treatment for 5 hours at 900°C for the unaltered solution and 5 hours at 700°C when the solution pH was raised to 9.00. A solubility limit of aluminum was determined for Bi1.6Pb0.4Sr2Nb2Ti1-xAlxO12 when x ≥ 0.4. Conductivity measurements at 1123 K of Bi1.6Pb0.4Sr2Ti1-xAlxO12 range from 4.76 × 10-3 S•cm-1 at x = 0.8 to 1.74×10-4 S•cm-1 at x = 0.1.

A carbon composite bipolar plate for PEM fuel cells has been developed that has high electrical conductivity, high strength, light weight, is impermeable, and has the potential for being produced at low cost. The plate is produced by slurry molding short carbon fibers into preform structures, molding features into the green body, and using chemical vapor infiltration to strengthen the material, give it high conductivity, and densify the surface to make it impermeable. Current efforts have focused on optimizing the fabrication process and characterizing prototypical components.

Tantalum is a tough, corrosion resistant metal, which would be suitable for use as bipolar plates for proton exchange membrane (PEM) fuel cells, if it was not for its high weight and price. Relatively thin tantalum coatings, however, can be deposited on other inexpensive and lighter weight metals, such as aluminum and steel, providing a passive protection layer on these easily formed substrates. We have successfully deposited, high quality α (body-centered-cubic, bcc) and β (tetragonal) phase tantalum coatings that were a few micrometers thick by dc magnetron sputtering on steel and aluminum. The growth of the thermodynamically preferred body-centered-cubic (bcc) tantalum phase was induced by a choice of deposition conditions and substrate surface treatment. The microstructure and corrosion resistance of the α-phase in an environment approximately simulating the electrochemical conditions used in a PEM fuel cell were investigated under potentiodynamic conditions. Preliminary potentiostatic measurements of a β-phase sample are also presented.

Oxygen-ionic and electronic conductive thin films with the composition of La0.6Sr0.4Co0.5Fe0.5O3-α (LSCF) were prepared on a porous alumina substrate by a chemical solution deposition (CSD) process and their oxygen permeating flux densities were measured. Thickness of the LSCF layer on the substrate was about 0.4 μm. Oxygen flux density of the LSCF sample was found to be 0.6 μmol·cm-2·s-1, however, time-dependent degradation of oxygen flux was observed. The CeO2 barrier layer between the LSCF layer and the substrate was effective in order to improve time-dependent degradation of oxygen flux.

Ternary oxides with general formula MMoO4 (where M is a 3d-transitional metal) were characterized as cathode materials for lithium rechargeable batteries by galvanostatic charge-discharge technique and cyclic voltammetry. The significant capacity fading after the first cycle of lithium insertion/removal takes place for different copper molybdates (standard a-CuMoO4and high-pressure modification CuMoO4 –III) corresponding to the irreversible copper reduction and formation of Li2MoO4 during the first discharge. X-ray powder diffraction data reveal the decomposition of pristine ZnMoO4 by electrochemical reaction, lithium zink oxide with the NaCl-type structure and Li2MoO3 seem to be formed.

The activation energies for poly(ethylene oxide) motion in a polymer clay composite are reported for the polymer intercalated and external to the clay. PEO intercalated into the clay is found to have a lower activation energy for motion but also a larger Arrhenius prefactor, by almost two orders of magnitude, than for PEO found external to the clay. Neutron scattering measurements confirm the presence of two environments and the effects of confinement on the mean square displacement of the PEO.

The preparation and oxygen permeability of composites of Ce0.8Gd0.2O2-ö (GDC) and spinel-type ferrites, MFe2O4 (M = Co and Mn) have been investigated. The composites of GDC -x vol% MFe2O4, where x ranged from 5 to 65, were prepared by a citrate-based liquid-mix technique. The composites were found to be almost fully densified by sintering at 1300 °C for 2 h. From TEM observations, the grain size of GDC and spinel-type phases was found to be less than 0.5 μm. In the case of M = Co, GDC - 25 vol% CoFe2O4 with a membrane thickness of 1.0 mm exhibited an oxygen flux density of 0.21 μmol·cm-2·s-1 under the P(O2) difference between He (20 sccm) and air at 1000 °C. Under reducing atmosphere of Ar-5%H2, the oxygen flux density of this composite increased up to 1.3 μmol·cm-2·s-1. Moreover, under Ar-10%CH4 gas flow, GDC - 15 vol% MnFe2O4 with a membrane thickness of 0.24 mm exhibited the oxygen flux density of 2 and 7 μmol·cm- · s- at 800 and 1000 °C, respectively.

The ionic conductivity and microstructure of selected compositions of the solid solution La1-xSrxCoO3-δ (LSC) were examined with respect to possible vacancy ordering phenomena. Homogeneous samples of LSC were prepared by the glycine nitrate process. The ionic conductivity was obtained as a function of the oxygen partial pressure (-3.5 ≤ log[p(O2)/atm] ≤ 0.5) using a recently developed galvanostatic polarization technique. At 825°C the p(O2)-dependence of the ionic conductivity of La1-xSrxCoO3-° (x = 0.4 and 0.6) shows a distinct maximum. Although this behavior has yet to be explained unambiguously it is indicative of decreasing mobility of ionic charge carriers, e. g. due to cooperative vacancy ordering. From the temperature dependence of the ionic conductivity of La1-xSrxCoO3-° (x = 0.6) activation energies at constant nonstoichiometry (0.20 ≤ ° ≤ 0.28) were obtained. As vacancy association and microstructure are presumed to play a significant role we combined the results of ionic conductivity measurements and electron microscopical investigations. HRTEM images revealed a superstructure within microdomains of about 100 nm in size.

Lithium ionic conductor, (La, Li)TiO3, has synthesized with La/Li-TiO2 amorphous spheres that were obtained by sol-gel and ion-exchange method, and succeeding La3+/Li+ partial ion exchange. In this work, La /Li ion exchange conditions were mainly investigated in order to obtain dense (La, Li)TiO3 ceramics that have highly ionic conductivities. La +/Li+ ion exchange behavior was changed with ion-exchange solutions, and the Li/Ti ratio was increased with an increase in ethanol/water ratio in the solvent used for La3+/Li+ partial ion exchange. The use of an adequate ethanol/water ratio resulted in La/Li-TiO2 amorphous spheres with the composition of La/Li/Ti=0.54/0.34/1.00, and sintering of the spheres at 1200°C for 5 h in air led to dense (La, Li)TiO3 ceramics which exhibit the conductivity of 4.0 × 10-3 S cm-1 at 25°C.

The dependence of ionic transport on structure and composition of perovskites LiyLa0.66-y/3TiO3 (0.09 ≤ y ≤ 0.5) and Li0.5-xNaxLa0.5TiO3 (0 ≤ x ≤ 0.5) has been analyzed by means of Neutron Diffraction, NMR and Impedance Spectroscopy. In the first series, ion conductivity displays a non-Arrhenius behavior, decreasing activation energy at increasing temperatures. Li mobility is accompanied by a considerable increase of Li thermal factor deduced from ND data. In the second series, local lithium mobility decrease monotonously with the sodium content at room temperature; however, long-range dc conductivity decreases sharply at x = 0.2 more than six orders of magnitude. This decrease on dc conductivity is discussed in terms of a three-dimensional percolation theory of vacant Asites. In this model, the number of vacant sites is controlled by the amount of Na and La of the perovskite.

Metastable CaSn2F6 has been prepared for the first time and characterized. It is a well crystalline material that leaches SnF2 in water to give the microcrystalline fluorite-type Ca1-xSnxF2 solid solution. In both materials, tin(II) is covalently bonded to fluorine, and thus carries a stereoactive non-bonding electronic pair. The electrical conductivity of CaSn2F6 was measured by the complex impedance method. The CaSn2F6 material was found to be a mixed conductor (τi = 0.50), with a F- conductivity a little below that of α-SnF2. On heating to 250°C, it decomposes irreversibly to give SnF2 and probably amorphous CaF2 (undetected).