Electromagnetic and thermoelectric characteristics of a sodium-cobalt oxide, NaxCoO2, were investigated. A precise control of Na nonstoichiometry was successfully facilitated by an unusual synthesis method named “rapid heat-up” technique. With increasing x, the absolute value of resistivity (ρ) monotonically decreased, while the value of thermoelectric power (S) increased, giving rise to a drastic enhancement in the thermoelectric power factor, i.e. S2 / ρ. Simultaneously enhanced thermoelectric power and reduced resistivity of the present compound are difficult to be understood within the framework of a conventional band picture. Moreover, for samples with the solubility limit Na content, i.e. x = 0.75, we discovered an unconventional electronic transition at Tm = 22 K, which may be induced by the strong-correlation effect of 3d electrons.

We show in this work the usefulness of the polymeric precursors method to obtain several Ba(BIII2/3W1/3)O3 (B = In, Y, Dy, Gd, Sm) complex perovskites. Solid resins obtained from solution were treated at different temperatures and characterized by XRD and thermal analysis. BaCO3 and Ba(NO3)2 were the only crystalline species found below 500°C. Tungstates with different stoichiometry evolve from the powdered precursors as the temperature is raised. Formation of perovskite-like phases is evident in all five cases, above 1000°C. XRD results suggest also that trivalent ions do not participate in chemical reactions below that temperature since the presence of any binary phase containing them could be confirmed.

Our research involves the solvothermal synthesis and characterization of new 3D open-framework and low dimensional inorganic materials. We focus on heavier group 14 elements to prepare structures that are analogous to aluminosilicate zeolites, but the main emphasis is to obtain cationic materials, a feat not possible with silicon oxides. We have successfully synthesized a series of novel compounds with Pb as building block: a cationic layered lead fluoride material (BING-5, Pb3F5NO3); a neutral, layered lead phenylphosphonate pyridine (BING-6); and a layered lead metamethylphenyl-phosphonate (BING-9). A molecular solid, tetrafluorodipyridine-germanium (BING-10) was also obtained. These structures are characterized by a variety of solid state techniques, including: powder X-Ray diffraction (PXRD), thermogravimetric analysis (TGA), UV-Vis spectroscopy and NMR. Our BING-5 material can exchange its interlayer NO3- for a variety of other anions. It is also stable to 450°C, which is far superior to organic resins that are still the standard for anion-exchange.

Inorganic nanoparticles of a variety of materials have been obtained by chemical methods. Under the kinetic control, small variations in the synthesis recipe may yield crystals of different sizes, shapes and structures. Co nanocrystals are of particular interest: besides achieving size control, at least three nearly isoenergetic crystal structures (face-centered cubic, hexagonal close-packed and epsilon) can be synthesized, and shape control (spheres, prisms, cubes, rods and disks) is also possible. Although shape and structure should be intrinsically related, the relationship between these two characteristics has not been deeply explored up to this moment. Here, we present our latest results on Co nanoparticles, analyzing the influence of some parameters on particle shape and structure. In particular, the influence of ligand type and temperature has been tackled.

This paper discusses the application of soft x-ray emission and resonant inelastic x-ray scattering as probes of the electronic structure of transition metal oxides. The results of studies on the narrow gap insulator CdO, and the Mott-Hubbard oxide Cr-doped V2O3, are reported. The O 2p valence band partial density of states for CdO has been measured, and emission due to the hybridization of the O 2p valence band states with Cd 4d shallow core level has been observed. For Cr-doped V2O3, the temperature induced metal-insulator transition in samples with 1.5% Cr was observed using soft x-ray emission, and both charge transfer and dipole forbidden d-d excitations were observed using resonant inelastic x-ray scattering.

A variety of titania microstructures have been synthesized using a swollen polymer matrix of polydimethylsiloxane (PDMS). The shapes and structures grown to date include spheres, ‘bowls’, ‘nets’ and ‘brain coral’ matrices. The PDMS polymer network can be swollen by one of a variety of organic solvents. These solvents create internal voids or spaces within the PDMS, of particular volume. These spaces can then be filled with metal alkoxide liquid. The metal alkoxide is then polymerized to form metal oxides, in a shape templated by the swollen PDMS polymer. The resultant product is a composite of metal oxide within a polymer. Some of the shapes can be removed mechanically or chemically. Methods of characterization include scanning electron microscopy (SEM) and optical microscopy. Potential applications of the shaped titania include catalysts, fillers, capsules, and chemical separators. The synthesis and characterization of these compounds will be discussed.

We have studied the synthesis of porous hydrophobic systems made from silica and zirconia. The silica systems have been grafted with alkyl-chlorosilanes. Alternative hydrophobic systems were also obtained by synthesis of colloidal monoclinic zirconia grafted with various alkyl phosphonates. The mechanism and the density of grafting were studied by solid state MAS NMR and nitrogen adsorption isotherms. The bulk thermodynamic properties of water are strongly dominated by the interfacial interactions at the surface of these porous solids. The penetration of water in these porous systems was studied by high pressure intrusion of water (water porosimetry between 0 and 100 MPa) into the hydrophobic pores. The amazing mechanical behavior of such water-porous body mixtures can find interesting applications for mechanical energy storage and dissipation.

The crystal structures of the Aurivillius phase ferroelectrics Bi4Ti3O12, BaBi4Ti4O15 and Ba2Bi4Ti5O18, containing perovskite-like layers consisting of three, four and five adjacent TiO6 octahedra, respectively, have been analysed using high-resolution powder neutron diffraction data. At 2K the structure of Bi4Ti3O12 can be successfully modelled in the orthorhombic space group B2cb, with no evidence of the monoclinic distortion in the ferroelectric phase suggested by previous single crystal studies. At 298K BaBi4Ti4O15 shows a subtle orthorhombic distortion, but without the octahedral tilting seen in related ferroelectric phases, and is refined in space group F2mm. At 298 K Ba2Bi4Ti5O18 adopts a tetragonal polar phase (I4mm), thus displaying a third type of polar distortion within this family. It is suggested that these differences arise from a ‘tolerance factor’ type mechanism whereby the increasing content of the large Ba2+ cation causes a shift from underbonding at the perovskite A-site to underbonding at the perovskite B-site resulting in a change in the mechanism of ferroelectricity from A-site displacements to B-site displacements, akin to the mechanism in BaTiO3.

The intercalation into MoO3 with TiO2 nanoparticles has been accomplished via the exfoliating-restacking route. The molybdenum oxide lithiated by LiBH4 is exfoliated in degassed and deionized water. And subsequent restacking of exfoliated MoO3 in the TiO2 nanoparticle solution results in TiO2-pillared MoO3. X-ray diffraction pattern indicates that the TiO2 nanoparticles are successfully intercalated in the interlayer of MoO3. The interlayer expansion of MoO3 with the Ad value of 11.2 Å is consistent with the size of TiO2 nanoparticle. Well-defined (00l) reflections reveal highly ordered lamellar character of TiO2-pillared MoO3. The pre-edge feature in the X-ray absorption spectrum of the TiO2-pillared MoO3 confirms that guest TiO2 in the interlayer of MoO3 is pillared in the form of anatase.

A variety of ion exchange techniques for Cu2P3I2 and its mixed pnictogen analog Cu2P1.8As1.2I2 have been studied. Ag2P3I2 is an existing material, previously prepared from Cu2P3I2 by ion exchange of Ag+ for Cu+ in aqueous medium. This method is compared to non-aqueous (ionic liquid) and solid state routes for ion exchange. Additionally, the new compound Ag2P1.8As1.2I2 with cell parameters a = 15.838(17) Å, b = 13.684(10) Å, c = 15.580(17) Å and β = 117.63(7)°, has been prepared by reaction of Cu2P1.8As1.2I2 with AgNO3 in aqueous solution.

Novel, volatile, stable, oxo-β-ketoesterate complexes of titanium, whose synthesis requires only an inert atmosphere, as opposed to a glove box, have been developed. Using one of the complexes as the precursor, thin films of TiO2 have been deposited on glass substrates by metalorganic chemical vapor deposition (MOCVD) at temperatures ranging from 400°C to 525°C and characterized by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. All the films grown in this temperature range are very smooth; those grown above 480°C consist of nearly monodisperse, nanocrystals of the anatase phase. Optical studies show the bandgaps in the range 3.4–3.7 eV for films grown at different temperatures. Thin films of anatase TiO2 have also been grown by spin-coating technique using another ketoesterate complex of titanium, demonstrating that the newly developed complexes can be successfully used for thin film growth by various chemical routes.

Via salt inclusion methods, we have recently isolated a new class of transitionmetal-containing hybrid solids that consist of a composite structure of covalent and ionic lattices. These new solids can be synthesized by conventional high-temperature, solid-state methods employing reactive molten alkali and alkaline-earth metal halide salts. Single crystal structure studies have revealed fascinating extended salt lattices that exhibit structural directing effects that give rise to a variety of nano-structured covalent oxide frameworks. Depending upon the composition of incorporated salt and the coordination environment of halide anions, resulting covalent lattices range from sheets, clusters, to porous structures. Due to the weak interaction between the two chemically dissimilar lattices, the salt lattice, in some cases, is removable showing reversible salt-intercalation at room temperature. In this report, we will demonstrate the utilities of salt-inclusion reactions in the formation of metal-oxide nanostructures in the selected compound families. We will also give some highlights on the recent discoveries of non-centrosymmetric solids via newly exploited salt-inclusion methods.

We have synthesized highly crystalline β-gallium oxide tubes, nanowires, and unique one-dimensional structures in the form of nanopaintbrushes using molten gallium and microwave plasma containing a mixture of monoatomic oxygen and hydrogen. Multiple nucleation and growth of gallium oxide nanostructures occurred directly out of molten gallium upon exposure to an appropriate composition of hydrogen and oxygen in the gas phase. Gallium oxide nanowires were 20 to 100 nm thick and tens to hundreds of microns long. In addition to these morphologies, we also report for the first time, non-template based synthesis of novel 2-D networks of crystalline gallium oxide nanowires and nanotubes. Demonstration of this technique with gallium oxide certainly presents a new route for synthesis of nanostructures of other important metal oxides such as indium oxide, tin oxide, and zinc oxide.

Electron nanodiffraction from single crystal domain of La1-xCaxMnO3 with 0.5 ≤ × ≤ 0.8 is carried out to study the charge ordering phase transition in this system. The melting processes of charge ordering structure in samples with x = 1/2, 2/3 and 4/5 are observed in-situ by increasing temperature from 93K – 298K. During the phase transition, electron diffraction results show that the nearly commensurate low-temperature charge ordering structure continuously evolves to incommensurate structure with directly decreasing sizes of charge ordered area. The picture of this phase transition is confirmed by the real space imaging. The real space images clearly show the introduction of charge ordering defects during the melting process in this sample.

Composites between ferroelectric material and a dispersed metal phase are of great interest due to the improvement in dielectric properties for such applications as high capacitance capacitors, non-volatile memory, ect. Using a colloidal method, Pt particles with a size of 3–5 nm were dispersed homogeneously in a PZT (PbZr0.53Ti0.43O3) matrix. No unwanted reaction phase between PZT and Pt during sintering at 1150 °C could be detected by X-ray diffraction. Electrical properties were investigated by impedance spectroscopy measurement. The effective dielectric constant increased remarkably as a power function of Pt volume content and can be described by the percolation theory. At 25 vol.% of Pt the dielectric constant of the composite is 4 times larger than that of pure PZT. The temperature dependence of the electrical properties is also influenced by the metallic phase fraction.

Raman scattering and X-ray diffraction were used to study the mechanism of the catalytic crystallization of carbon and metal dusting. The following new mechanism is proposed for metal dusting and the growth of carbon filaments. Carbon cannot crystallize well by deposition from carburizing gases at low temperature without catalytic activation because of its strong C-C bonds and high melting temperature. The poorly crystalline carbon has higher free energy than that of good crystalline carbon. To form good crystalline carbon, carbon atoms have to dissolve, diffuse through metal particles, and crystallize on a proper lattice plane that can act as a template to help the epitaxial growth of carbon crystals. Metal particles are liberated from the pure metal and alloys in this process, which leads to metal dusting attack. The decrease of free energy from highly disordered to well crystalline carbon is the driving force for metal dusting and carbon filament growth through metal particles.

Stoichiometric K0.5Na0.5NbO3 solid solution(KNN) was prepared by solid-state synthesis from alkaline carbonates and niobium oxide. Thermal decomposition of the powder mixture occurs upon heating to 700 °C followed by crystallization of the perovskite phase. After sintering at 1100 °C, 2h the stoichiometric KNN reaches 94 % of theoretical density. Dielectric constant of stoichiometric KNN is 620, and the losses 0.03.

The phase equilibria and thermodynamic properties of the ternary Ni-Al-Ta system on Ni-rich side were analyzed. Thermodynamic descriptions of the liquid, γ-fcc, γ'-L12, and π-Ni6AlTa phases were obtained using the CALPHAD (CALculation of PHase Diagrams) technique. The thermodynamics of γ-fcc and γ'-L12 phases were modeled with a single Gibbs energy function taking into account the crystallographic relation between the two phases. The ternary interaction parameters of the liquid and fcc phases were also determined. The calculated phase diagrams of the ternary Ni-Al-Ta system show a good agreement with experimental data.

Rare earth-based mixed-anions (O, S, F) compounds have been prepared by solid state route. The structures have been determined on the basis of powder diffraction (X-ray/neutrons) refinement and/or single crystal analysis. They have been described as a stacking of [Sx] 2x- layers and fluorite type blocks. The evaluation of the rare earth environment (bondlength, number of neighbors) can be directly related to the bandgap and to the UV-visible absorption in the La-based compounds.

A series of derivative compounds based on the layered parent phase CrWN2 have been synthesized using a complexed precursor synthesis route. X-ray diffraction analyses demonstrate that both the chromium and tungsten display mutual substitution for one another and can also undergo considerable extensive replacement by a wide variety of cation species without significantly altering the original layered structure of the parent dinitride compound. The precursor approach employed here appears to offer a ready technique for exploring compositional phase space in layered nitrides of this type.