A comparison of calculated and experimental temperature variation of elastic constants were used to predict types of oxygen—vacancy dopant clusters in yttria stabilised cubic zirconia, which serves as an electrolyte in solid oxide fuelcells. Such clusters were incorporated in supercells set up for molecular dynamics studies, where oxygen transport properties were investigated at concentrations of 9.4 and 24 mol % of yttrium oxide and up to 1600K.

The thin films of 4% Y2O3 doped CeO2 have been deposited on different substrates of Pd film/(001) LaAlO3, Pd film/r-cut sapphire, and Pd film/Quartz using an e-beam deposition technique. The microstructures and electrical properties of the films were investigated by means of x-ray diffraction, transmission electron microscopy, and ac impedance spectroscopy. Both textured and polycrystalline films were produced on different substrates. A brick layer model was adopted to correlate the micro structure and electrical property of the films. Only the grain boundary arc was observed in the film complex impedance plots. The conductivities of the films were similar to the conductivity of 6% Y2O3 doped CeO2 bulk grain boundary because of lower preexponential factor, although the activation energies were smaller than that of bulk grain boundary. The resistive gram boundaries were found to dominate the conductivities of the films.

In this study, mechanochemical milling (also known as mechanical alloying), has been used as an alternative means of synthesis of ceramic metal oxide electrolytes at room temperature and compared to the conventional calcination methods. The oxide electrolytes prepared by mechanical milling, were, the lanthanide-doped fcc Bismuth Oxides and Cerium Oxides, both of which are oxygen deficient. Conductivities for some of these milled oxides, measured by the four probe technique, were found to be enhanced when compared to those for conventionally prepared materials.

The A3+2B4+2O7 pyrochlores have fast-ion conduction properties that make them attractive candidates for applications in fuel cells. Rietveld powder-profile analysis of x-ray diffraction data has been used to determine structural parameters for Gd2(Ti1-ySny)2O7 solid solutions (y = 0.20, 0.40, 0.60, and 0.80) for correlation with composition-dependence of the specimens' electrical conductivity. In accord with Vegard's law, the lattice constants increase linearly with y as the larger Sn ion replaces Ti4+. The structures in the system remain remarkably ordered in view of the fact that it had been suggested that increasing the average radius of the ions that occupy the B4+ site relative to A3+ drives the system toward a disordered defect-fluorite state. A small but significant increase in mixing of the occupancy of the cation sites was found with increasing y to a maximum of [GdB] = 0.05. We could detect no significant disorder in the anion array. The activation energy and pre-exponential term for oxygen ion conduction were found to increase linearly and exponentially with y, respectively, such that at a given temperature, the ionic conductivity changes by less than an order of magnitude across the system. The behavior is in marked contrast to other systems where the substitution of a larger cation in the B site increases conductivity by up to three orders of magnitude as a consequence of substantial disorder that is introduced in both the cation and anion arrays.

The high protonie conductivities of barium cerium gadolinium perovskites (Ba(Ce1-xGdx)O3-x/2, O < x < 0.2) has led to their incorporation as electrolytes in fuel cells operating at 873–1073K. In an effort to develop new mixed-conducting electrodes that are compatible with the cerate electrolyte, we have examined the electrochemical properties of Pr-doped barium gadolinium cerate. The Pr doping increases the electronic contribution to the total conductivity and for Ba(Ce0.5Pr04Gd0.1)O2.95, a conductivity exceeding ≈ 0.1 S/cm at 1173K in dry air has been obtained. EMF measurements indicate the presence of both protonie and oxygen ionic contributions to the conductivity in the Pr substituted samples. The cathodic overpotentials of Ba(Ce1-(x+y)PryGdx)O3-x/2 mixed conductors on a Ba(Ce0.8Gd0.2)O2.9 electrolyte have been measured. Ba(Pr0.8Gd0.2)O2.9 has the best cathodic performance and could be a viable alternative to Pt cathode for a barium cerate based fuel cell.

Electrical conductivity of the mixed-conducting Sr-Fe-Co-O system was investigated at elevated temperatures and various oxygen partial pressures (pO2). The system exhibits not only high combined electrical and oxygen ionic conductivities but also structural stability in both oxidizing and reducing environments. The conductivity of SrFeCo0.5Ox increases with increasing temperature and increasing pO2, within our experimental pO2 range (1 ≥ pO2 ≥ 1O-18 atm). p-type conduction behavior was observed. The activation energy of which increases with decreasing pO2. A model of the defect chemistry in the Sr-Fe-Co-O system is proposed. The pO2-dependent conducting behavior can be understood by considering the trivalent-to-divalent transition of the transition metal ions in the system.

Superionic PbSnF4 can be prepared using a variety of different methods. It crystallizes in various different unit-cells. All structures are closely related to that of the fluorite type structure, with various degrees of order/disorder and different types of superstructures. Reaction of lead(ll) nitrate and stannous fluoride in water gives highly stressed and highly oriented tetragonal α-PbSnF4, however, in HF/H2O, it gives orthorhombic O-PbSnF4, which is also stressed but less. Reactions of solid α-PbF2 with an aqueous solution of SnF2, in excess SnF2, also gives stressed α-PbSnF4. Solid state reactions of SnF2 and PbF2 give unstressed and much less oriented α-PbSnF4 at 250°C, whereas tetragonal β-PbSnF4 is obtained above 270°C and is quenchable to ambient temperature. At 390°C, cubicy-PbSnF4 is obtained, however, this is not quenchable. Ball milling of o-PbSnF4 gives stressed α-PbSnF4, and ball milling of a- and β-PbSnF4 gives microcrystalline γ-PbSnF4. Annealing the latter gives unstressed and non oriented α-PbSnF4. Stirring a slurry of microcrystalline γ-PbSnF4 in water gives α-PbSnF4 except the one originating from o-PbSnF4, which gives back o-PbSnF4. The texture of these phases, and therefore the macroscopic properties related to it, can be drastically modified by modifying the method of preparation.

Galvanostatic polarization of a mixed conductor located between an ionically blocking electrode and an electronically blocking electrode in an asymmetric electrochemical cell is treated in detail. Evaluation formulae for the determination of the chemical diffusion coefficient of mixed conductors with comparable ionic and electronic transport numbers are introduced. They allow the determination of the chemical diffusion coefficient of Ag1.92Te as a function of composition at 160°C from galvanostatic polarization and depolarization experiments on the asymmetric cell Ag | AgI | Ag1.92Te | Pt. The chemical diffusion coefficient shows composition dependent values between 0.002 and 0.004 cm2s-1. The electronic transport numbers are obtained independently from four-point van der Pauw measurements with typical values around 0.8–0.9.

The exchange current observed at porous metal electrodes on sodium or potassium beta"-alumina solid electrolytes in alkali metal vapor is quantitatively modeled with a multi-step process with good agreement with experimental results. No empirically adjusted parameters were used, although some physical parameters have poor precision. Steps include: (1) diffusion of Na+ ions to the reaction site; (2) stretching of the Na+ ionic bond with the β3"-alumina surface to reach a configuration suitable for accepting an electron to form a surface bound Na0 atom; (3) electron tunneling from the Mo electrode to the ions; and (4) desorption of Na0 atoms weakly bound at the reaction site on the β"-alumina surface; (5) electron tunneling between Na0 or Na+ on the defect block and (6) Na0 and/or Na+ mobility on the spinel block surface may extend the reaction area substantially.

The rate is increasingly dominated by the region close to the three-phase boundary as temperature increases and the rate near the three-phase boundary increases fastest, because desorption has a higher energy than reorganization. At high temperatures, surface diffusion of Na+ ions from the defect block edges to the spinel block edges is responsible for an increase in the total effective reaction zone area near the three-phase boundary.

Structure of β"-alumina has been studied through atomistic simulation. Distribution of Mg2+ in the spinel blocks, Na+ as well as Nd3+ in the conduction planes have been calculated and compared with the structure models derived experimentally. Mg2+ ions, as the stabilizer of β"-alumina structure, prefer to occupy the tetrahedral Al(2) sites in the spinel block. Two configurations for Mg2+ distribution are proposed. Due to the presence of Mg2+, oxygen ions in or adjacent to the conduction plane, O(5), O(4) and O(3), are slightly displaced from their original sites, leading to the removal of the local symmetry at the mO site. Strongly affected by the Mg2+ distribution, Nd3+ions, originally introduced into the BR site in the conduction plane, are found to move towards the distorted mid-oxygen sites, which is in excellent agreement with the previous estimate from spectroscopie study.

The glass-ceramics of the phosphorus containing Na5RSi4O12type (R=rare earth) Na+-superionic conductors (Narpsio-V) in the system Na2O-Sm2O3-P2O5-SiO2 were prepared by crystallization of glasses with the composition Na3+3x-ySm1-xPySi3-yO9. The optimum conditions for crystallization were discussed with reference to the conduction properties and the preparation of uncracked bulky glass-ceramic Narpsio-V. The ionic conductivity of the glass-ceramic Na3.9Sm0.6P0.3Si2.7O9 at 300°C was drastically enhanced from 2.38×10-2 S/cm to 7.15×10-2 S/cm upon implantation of 200 keV Na+ ions to a fluence of 1 × 1015 cm-2.

LiSbO3 thin films have been prepared by the sol-gel process with metal alkoxides using a spin-coating method. The (Oll)-oriented and randomly oriented LiSbO3 thin films are obtained by the precursor film crystallizing under an atmosphere of a flowing mixture of water vapor and oxygen, and an air atmosphere, respectively. The two different atmospheres also affect the crystallization temperature of the films. The electrical conductivity of the (Oll)-oriented LiSbO3 thin film is approximately one order of magnitude larger than that of the randomly oriented LiSbO3 thin film in the temperature range of 380 to 600°C.

The relation between the structure and the lithium ion conductivity in perovskite-type oxides ABO3 was investigated from the viewpoint of the the arrangement of A-site ions. It was showed that the conductivity in La2/3-xLi3x□1/3–2xTiO3 is strongly influenced by not only the concentration but also the ordered arrangement of skeletal A-site ions. Further the activation energy for ion conduction was found to be dominated by the covalency of B-O bond in addition to the bottleneck size.

Powders and films of amorphous, cubic and monoclinic antimonic acids are prepared. Their water sorptioh isotherms and the water desorption spectra are measured. The protonie conductivities are very sensitive to water vapor pressure and are discussed with the amount of water. The amorphous and cubic antimonic acids contain larger amounts of water than the monoclinic acid, which can be attributed to the existence of micropores in the structures.

The synthesis, characterization and electrochemical performances of lithiated nickelate and cobaltate doped with Al and B are reported. The synthesis involves solid state reaction between lithium hydroxide, nickel or cobalt oxides and several sources of aluminum and boron. Careful selection of precursors and heat treatment conditions are required to prepare single phase impurity free samples. X-ray diffraction and Rietveld refinement analysis indicate that the layered structure is preserved upon considerable substitution of aluminum and boron. X-ray diffraction line intensities and positions remained in good agreement with the space group. The IR spectra of the samples indicate formation of compressed CoO6 and NiO6, and elongated LiO6 octahedra. The IR vibrational mode of the LiO6 remains in the 200–300 cm-1 and the vibrational modes of the MO6 expand over 400–650 cm-1. Results of long charge-discharge cycling of the samples as cathode materials in lithium cells showed long cycle life. The capacity of the electrodes upon substitution were reduced almost linearly as the concentration of substitution was increased. The solubility limit for the formation of solid solutions upon substitution of Al and B in LiNiO2 and LiCoO2 was found to be around 25%. Specific capacities of the samples were between 120 to 160 mAh/g depending on the amount of substitution.

We report synthesis, crystal structure, lattice dynamics, and electrochemical features of the lithiated manganese oxide spinel prepared through solid state reaction by careful selection of precursors and synthesis conditions. Elemental analysis shows that the material is a lithium-rich spinel phase. X-ray diffraction data and Rietveld refinement indicate formation of a single phase, impurity free, normal spinel of LiMn2O4. Lattice dynamics have been investigated by vibrational spectroscopy and group theoretical analysis has been carried out. Electrochemical performances of the lithiated spinel manganese oxide have been investigated, and the voltage profile of the cathode during lithium intercalation-deintercalation processes, close to equilibrium, has been obtained. The upper 4-volt plateau provides over 130 mA h/g with an excellent cyclability.

The mild hydrothermal decomposition of aqueous permanganate solutions has been found to lead to new layered manganes oxides. In the case of alkali permanganates, AMnO4, layered birnessite-type compounds are formed with the general formula - AxMnO2•nH2O. These compounds have R 3 m rhombohedral structures analogous to the layered disulfides. The water is reversibly lost on heating, and the compounds readily intercalate lithium ions in a reversible manner. In the case of the hydrothermal decomposition of tetramethylammonium permanganate in the presence of nickel, the new compound NiMnO3 is formed that has a novel structure. This compound also has interesting magnetic properties, being a paramagnet above 111K and a ferromagnetic below that temperature.

A comparative study of lithium insertion in W4Nb26O77 and W3Nb14O44, two block structure type phases, has been carried out. This process is, in both cases, reversible for a similar number of lithium ions incorporated to total metal atoms ratio (Li/ΣM), 1.15 in W3Nb14O44 and 1.23 in W4Nb26O77. No significant structural changes are seen by X-ray diffraction upon insertion. Sodium insertion in W3Nb14O44 has been also studied observing a substantial reduction on the number of ions incorporated when compared with lithium (Na/ΣM: 0.03).

Reversible coloration occurs in tungsten trioxide (WO3) films when double injection of electrons and ions is provided in its volume. Experiments were performed in electrochemical cell with liquid electrolyte, where protons were used for injection in amorphous WO3 films. Kinetics of electrochromic coloration process was studied in spectral range of 300 nm to 1200 nm. Dependence of optical density on injected charge was found to be different in various spectral regions for coloring and bleaching. Infrared vibrational spectra of electro-chemically colored crystalline and amorphous WO3 were obtained. Electronic structure features of amorphous WO3 related to electorchromism are discussed.

Physical properties of polycrystalline materials are controlled by intergranular as well as intragranular effects. In most cases materials' properties adhere to the bonding character of internal interfaces and plasticity of bulk parts. The nature of interfaces is in general difficult to understand, although they have far reaching consequences to overall properties of processed materials. To properly understand the effects brought by such interfaces one has to correlate particular properties with their local chemistry and structure. The availability of modern instrumentation that can provide a detailed chemical and structural information down to a subnanometer scale has helped greatly in tackling many fundamental problems in materials science. Our systematic studies of several metal/ceramic and ceramic/ceramic interfaces has given us a wealth of information that brings us closer to the answer on the formation mechanisms of the internal interfaces and other structural transformations in materials.