The preparation of dense, high conductive electrolyte layers is important for the development of intermediate temperature solid oxide fuel cells and other devices based on oxygen-ion conductivity. Thus a number of techniques have been used to produce these structures. This study makes use of one of these methods to produce dense nanocrystalline 0.1 to 1 micron layers of zirconia.

Polymeric precursors were used to prepare zirconia films with different level of yttrium substitution. The films were annealed at a series of temperatures in the range of 400 to 1000°C and were characterized via scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that initially (after 400°C annealing) the films had cubic structure and grain size of ∼5 nm regardless of Y content. The situation changed when the annealing temperature was increased. Y (16mol %) stabilized zirconia (YSZ) did remain cubic over the entire temperature region investigated (up to 1000°C), but for compositions with lower Y content changes in crystal structure occurred. The samples with 4 and 8mol% Y transformed to the tetragonal phase at about 700°C, and undoped zirconia became monoclinic at the same temperature.

The results were compared with sintered zirconia and it was shown that the behavior of thin films is quite similar to that of the sintered material, if the annealing temperature was high enough (>700°C). The main differences between polymeric prepared films and sintered material are the existence of the cubic structure at low temperatures (< 600°C) and lower transition temperatures to the high temperature phase, which can be explained by small initial grain size in polymer-derived zirconia.

Germanium nitride (Ge3N4) was examined as a potential negative electrode material for Li-ion batteries. The electrochemistry of Ge3N4 versus Li showed high reversible capacity (500mAh/g) and good capacity retention during cycling. A combination of ex-situ and in-situ x-ray diffraction (XRD), ex-situ transmission electron microscopy (TEM) and ex-situ selective area electron diffraction (SAED) analyses revealed evidence supporting the conversion of a layer of Ge3N4 crystal into an amorphous Li3N+LixGe nanocomposite during the first lithiation. The nanocomposite was electrochemically active via a reversible Li-Ge alloying reaction while a core of unreacted Ge3N4 crystal remained inactive. The lithium/metal nitride conversion reaction process was kinetically hindered resulting in limited capacity. Mechanical milling was found to improve the material capacity.

The electrical conductivity and oxygen permeability of transition-metal-doped (Ba0.3Sr0.2La0.5)2(In1-xTMx)2O5+ö (TM = Fe, Co, Mn and Sn; 0 ≤ × ≤ 0.5) have been investigated. The X-ray diffraction analysis revealed that all the samples had a cubic perovskite-type structure due to La3+ doping on the alkaline earth site. For Fe-doped specimens, the lattice parameter of 0.414 nm for (Ba0.3Sr0.2La0.5)2In2O5+δ linearly decreased with increasing the Fe content, suggesting the incorporation of Fe into the matrix phase. Fe-doping for the In site enhanced the p-type conduction under a wide P(O2) range, and the p-type conductivity increased with increasing the Fe content without decreasing the ionic conductivity. The oxygen permeability was measured under the P(O2) difference between helium and air in the temperature range of 800 ∼ 1000 °C. For the Fe-doped specimens, the oxygen flux density of j(O2) increased with increasing the Fe content, and a maximum value of 0.5 μmol·cm-2·s-1 was attained at 1000 °C for the membrane thickness of 1.0 mm.

The effect of substitution on the intercalation properties of anatase-structured titania has been investigated in first principles calculations. Ti4+-ions were substituted by Zr4+, Al3+ and Sc3+ respectively and O2- -ions by N3-. For each compound the open circuit voltage profile (OCV) was calculated and compared to anatase. Lithium intercalation proceeds as in pure anatase through a phase separation into a Li-rich and a Li-poor phase in all cases examined here. The Li-content of the phases depends on the nature of the dopant and its concentration. Substitution by N3--ions does not lead to lower potentials, whereas doping with trivalent Sc3+- and Al3+- ions decreases the intercalation voltage. Substitution by tetravalent Zr4+-ions within the range of solubility does not significantly affect the OCV of anatase. A correlation is observed between the predicted equilibrium voltage and the participation of the Ti4+-ions in accommodating the donated electron density upon lithiation.

Results of a quasi-elastic incoherent neutron scattering study of the influence of confinement on polyethylene oxide (PEO) and (PEO)8Li+[(CF3SO2)2N]- (or (POE)8LiTFSI) dynamics are presented. The confining media is Vycor, a silica based hydrophilic porous glass. We observe a strong slowing down of the bulk polymer dynamics under presence of Li salt. The confinement also affects dramatically the apparent mean-square displacement of the polymer. As supported by DSC measurements, the PEO melting transition at 335 K is strongly attenuated under confinement, suggesting that confinement modifies the global structure of the system, increasing the fraction of amorphous PEO by respect to crystalline phase. Local relaxational PEO dynamics is successfully described by the DLM (Dejean-Laupretre-Monnerie) model usually used to interpret NMR spin-lattice relaxation time data. The scattering vector dependence of the correlation times deduced from inelastic neutron scattering data is found to obey a power-law dependence. DSC and preliminary ionic conduction measurements are also presented.

This paper describes the results of an investigation of the structure and composition of core-shell gold and alloy nanoparticles as catalytically active nanomaterials for potential fuel cell catalysis. Centered on the electrocatalytic methanol oxidation, we show three sets of results based on electrochemical, surface, and composition characterizations. First, electrochemical studies have revealed that the nanostructured catalysts are active towards the electrooxidation of methanol and carbon monoxide. Second, X-ray photoelectron spectroscopy (XPS) data have shown that the organic encapsulating shells can be effectively removed electrochemically or thermally, which involves the formation of oxides on the nanocrystals. Thirdly, direct current plasma - atomic emission spectrometry (DCP-AES) has revealed insights for the correlation of the composition of alloy nanoparticles with the catalytic activities. Implications of these results to the design of nanostructured catalysts will also be discussed.

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.

An intermediate temperature solid oxide fuel cell (SOFC) electrolyte film of La0.8Sr 0.2Ga0.8Mg0.2O2.8 (LSGM) was fabricated using a plasma spray process. The microstructure and phase were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical behavior of the thermal sprayed LSGM film was investigated using electrochemical impedance spectroscopy (EIS). The study indicates that thermal spray can deposit a dense LSGM layer. It was found that the rapid cooling in the thermal process led to an amorphous or poor crystalline LSGM deposited layer. This amorphous structure has a significant effect on the performance of the cell. Crystallization of the deposited LSGM layer was observed during annealing between 500–600 °C. After annealing at 800 °C, the ionic conductivity of the sprayed LSGM layer can reach the same level as that of the sintered LSGM.

Cost effective high volume manufacture (HVM) is a major challenge to the success of solid oxide fuel cells (SOFCs). More than fifteen processing methods have been reported in the literature many of which could be used in various combinations to create the desired product characteristics. Modeling tools are needed to aid in the selection of the appropriate process combination prior to making expensive investment decisions.

This paper describes the development of a multi-process cost model that permits the comparison of manufacturing cost for different processing combinations and various materials. Two specific processing methods are discussed, tape casting and screen printing.

The results are compared with data and experience from the fuel cell and electronic packaging industries. Initial comparisons show good agreement with this experience base. Sensitivity of manufacturing costs to SOFC performance requirements such as maximum power density and operation temperature is investigated.

In order to better understand the cycling mechanism of metal alloy anodes, and to mitigate the capacity fade observed in lithium battery use a study of simple systems was initiated. Tin foil and tin-bismuth mixtures were chosen because there is no need for conductive diluents or binders so that the intrinsic behavior could be observed. A pure tin foil was found to react rapidly with lithium, ≥ 3 mA/cm2, and with no capacity fade for over 10 cycles. This is better than tin powder or electrodeposited tin. After the first cycle, the foil reacts with Li following a stepwise formation of different alloys as dictated by the thermodynamics. Incorporation of bismuth into the foil increased the capacity fade after the first few cycles, with the eutectic composition Sn0.57Bi0.43 having better capacity retention than the Sn0.5Bi0.5 composition. XRD and SEM-EDS shows that bismuth is rejected from the tin rich phase during lithium insertion and is not reincorporated on lithium removal, just as expected from the phase diagram.

We describe the measurement of electronic conductivity of solid oxide electrolytes by a modified Hebb-Wagner technique based on the use of blocking microelectrodes. Results are presented for a couple of typical solid oxide electrolyte systems mainly derived from ceria and lanthanum gallate. The examples demonstrate a good resolution of the microelectrode technique in particular within the electrolyte domain, i.e. around the minimum of the electronic conductivity. This made possible the detection of deviations from the predicted oxygen partial pressure dependence of simple defect models for the concentrations of electrons and holes. The observed deviations from these defect models, at least partially, reflect the overemphasized ideality of the usually applied semiconductor model.

Whereas the effect of dissolved transition metals with variable valence states such as Fe, and Co on the electronic conduction is well known, it was unexpected to find a strong concentration dependent effect of dopants like Y3+ and Zr4+ in ceria or Mg2+ and Sr2+ in the gallates upon the electronic conductivity within the electrolytic domain. Ions like Y3+ and Zr4+ cause a shift and a partial broadening of electronic states in ceria based materials. Indications have been found for band tailing due to high defect concentrations. In some cases, the dopants cause the appearance of additional localized electron states in the gap which give rise to weak superimposed maxima of the electronic conductivity at a particular oxygen partial pressure within the electrolytic domain.

Accordingly, one cannot expect that electronic conductivities of solid electrolytes are insensitive to a changing concentration of stabilizers such as Y, Ca, etc. For instance, even a moderate doping of ceria by zirconia leads to a considerable electronic excess conductivity in the electrolytic domain.

The dynamics of the mobile ions in materials with disordered structures are a challengingly complicated many-particle process. In this paper, we consider characteristic frequency-dependent conductivities and permittivities of such materials and show that they can be well reproduced within the framework of the MIGRATION concept. The meaning of the acronym is MIsmatch Generated Relaxation for the Accommodation and Transport of IONs. In the MIGRATION concept, we attempt to grasp the essence of the ion dynamics in a simple set of rules which convey a physical picture of the most relevant elementary processes. The rules are expressed in terms of three coupled rate equations which then form the basis for deriving frequency-dependent model conductivities and permittivities.

A statistical model has been employed to determine the optimal sintering times and temperatures for Bi2Sr2Nb2TiO12. The phase of interest was made in pure form by solid-state synthesis. Bi2O3 was used as a sintering aid to decrease sintering temperatures and increase densification. The amount of Bi2O3 added and the sintering temperature had a statistical impact on density, while the heat treatment time did not.

A ramsdellite with composition LiCrTiO4 has been obtained by heating the spinel of same composition to high temperature. The new ramsdellite has been investigated in view of its possible use as an electrode material in lithium rechargeable batteries. Lithium can be partially extracted from ramsdellite LiCrTiO4 and further intercalated into, by contrast to the spinel of same composition. The average operating voltage during lithium extraction is 4 Volts vs. lithium, and the process produces a specific capacity of 90 mAh/g at 0.1 mA/cm2. On the other hand, upon reduction from open circuit voltage, lithium can be reversibly intercalated into the ramsdellite polymorph at ca. 1.5 V vs. lithium yielding a rechargeable capacity of 110 mAh/g at 0.1 mA/cm2.

Experimental results from electrical conductivity relaxation (ECR) measurements on SrFeO3-x are described. Values of Dchem and kchem were obtained by monitoring the variation of the time dependence of the electrical conductivity after an abrupt change in the oxygen partial pressure. Values for the oxygen ion and vacancy diffusion coefficients were calculated from the measured thermodynamic factors and compared with those of other compositions in the series La1-xSrxFeO3-x. The surface exchange coefficients, kchem and kex were also determined.

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.

As interest in high temperature electrochemical membrane devices for energy and gas generation has intensified, it has become apparent that developing an appropriate method of hermetically joining the ceramic and metallic components in these devices will be critical to their success. A recently developed technique referred to as reactive air brazing (RAB) has shown promise in the joining of components for planar solid oxide fuel cells (pSOFC) and oxygen generators. In the study described below, the relationship between braze composition, substrate wetting, and joint strenth was investigated to gain further understanding of the RAB process. It was found that braze wettability and joint strength are inversely related for the simple binary Ag-CuO braze system.

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.

Novel lithium ion battery anode materials consisting of carbon-coated silicon were prepared. Chemical vapor deposition (CVD) methods were used in the syntheses of these composite materials with toluene being used as the precursor for carbon coatings on silicon powder. The temperature of carbon deposition was 950°C and the deposition time was 30 min for powdered substrates. Carbon-coated silicon powders were analyzed by HRSEM, TEM, and Raman spectroscopy. Coin cells were made and cycled to evaluate the electrochemical performance of carbon-coated silicon powders. Coated materials performed well during the initial coin cell testing. Silicon wafers (orientation <111>) were also used as the substrates for carbon coatings. Silicon wafers were coated for 40 seconds at 950°C. Auger spectroscopy and XPS depth profiling were used to analyze the thin films of toluene-derived carbons on silicon wafers.

We investigated the dielectric properties of La0.53Na0.41-xLixTiO3 (x<0.26) and 7Li NMR for La0.53Na0.34Li0.17TiO3 (x=0.17). As results, relaxation process were observed at 40 K and 225 K for La0.53Na0.34Li0.17TiO3 (x=0.17). The activation energy of the dielectric relaxation at 40 K is in accordance with the that obtained by NMR measurement. On the other hand, the activation energy of the relaxation at 225 K accords with that of the Li ion conduction in the low temperature region for (La,Li)TiO3. These results indicate that different transport mechanisms intrinsically exist in (La,Li)TiO3 and one of reasons for the non-Arrhenius behavior of (La,Li)TiO3 is that the transport mechanism mainly related to the dc conductivity varies with the temperature.