A new molecular sieve GUS-1 is synthesized under hydrothermal conditions using a new organic compound acting as structure-directing agent. The structure determination reveals a framework with one-dimensional 12-membered ring channels running parallel. The structure exhibits the same channel net as zeolite ZSM-12 and shows the same projection of the framework along the pores as mordenite.

The synthesis of compounds of the type CsAIIIMIVO4 and (Cs,Rb)AIIPO4 (AIII = Al, Ga, Fe; AII = Ni, Co, Cu; M = Si, Ge, Ti,), using gel decomposition techniques at high temperatures is described. Several new materials in this family have been characterised using powder X-ray diffraction and are shown to adopt the zeolite ABW framework topology. Evidence for the large monovalent cation templating the formation of the ABW framework is presented. Extension of the method to other AIII and MIV (A = Mn, Co, B, In; M = Sn, Zr) framework cations, which are known to adopt tetrahedral geometry in other structures, has proved unsuccessful.

Ni and Co K-edge X-ray absorption spectra of LiNi0.8Co0.2O2 have been collected using in situ coin cells. To investigate the electronic and structural changes accompanied by the capacity fading during electrochemical cycling and keeping batteries at high temperatures, the cells with different cycling states and keeping conditions (temperature, time) were prepared. Upon charging the cell, the Ni and Co K absorption edge shifted towards higher energy, and the good correlation between the range of chemical shifts upon charging and the capacity of the cell was observed. From quantitative analysis of EXAFS data, it was revealed that the capacity fading is closely related to the Jahn-Teller distortion of the NiO6 octahedron.

Hydrothermal reactions using NaBiO3·nH2O produced a variety of newbismuth oxides that were not prepared by high temperature reaction. Some of them have pentavalent bismuth such as Bi2O4O, LiBiO3, ABi2O6 (A = Mg, Zn) and AgBiO3. When using transition metal or rare-earth metal solutions, new bismuth oxides with trivalent bismuth were obtained. In the case of Cr(NO3)3 solution a chromium bismuth oxyhydroxide, HBi3(CrO4)2O3, was prepared at 180°C, while in A2CrO4 (A = Li, Na, K) solution a new bismuth chromium oxide, Bi8(CrO4)O11, was prepared above 180°C. When A2MoO4 (A = Li, Na, K) solution was used, a new phase appeared above 220°C. By using A2WO4 (A = Li, Na, K) solution β-Bi2O3 and Bi2WO6 were obtained above 220°C.

We simulate both the amorphous cluster a-C57H52 that contains 5-atom planar rings and 6-atom boat-type rings and the crystalline cluster c-C59H60 that contains only chair-type 6-atom rings, as in the tetrahedral crystal (diamond structure). We carry out ab initio calculations using the DMol code and report the total energy, the electronic (density of states) structure and optical properties of the two types of clusters, with and without relaxation of the structures, in order to see the effect of the types of atom rings found in the amorphous structures compared to those found in the crystal structure.

Extended two-dimensional coordinate covalent networks have been formed at an air-water interface by condensing a Langmuir monolayer of an amphiphillic pentacyanoferrate(III) complex and aqueous nickel(II) ions. The cyanide-bridged arrays were transferred to solid supports by the Langmuir-Blodgett (LB) technique. The resulting thin films were structurally characterized by UV-Vis and FT-IR spectroscopies, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and SQUID magnetometry. Magnetic measurements on the thin films transferred to Mylar show evidence for ferromagnetic exchange interactions between the S = 1/2 Fe(III) and S = 1 Ni(II) centers.

It is well known that vanadium oxides readily form open structures that defines the potential use of vanadium compounds as cathode materials for lithium batteries. In order to stabilize open frameworks during electrochemical cycling and improve their performance, vanadium oxide can be modified with other transition metals. This work presents the structural analysis of vanadium oxide frameworks modified with Mn and Zn as well as reporting on several interesting new structures, such as TMA4[Zn4V21O58] and NaMn(VO3)4·2H2O.

A theoretical study of the optical excitation processes in cetineites is presented. This new exciting class of crystals with tubular structures displays photoconductivity, which strongly depends on the presence of guest molecules within the tubes. Based on self-consistent electronic structure calculations we present calculated dielectric function and photoelectron spectra of the (Na;Se) cetineite with the tube fllled with different guest molecules. Calculations are performed with the extended linear augmented plane wave kp method. The configuration and the arrangement of the filling molecules is derived from available crystallographic data and from heuristic arguments on chemical binding.

The crystal chemistry of a number of Fe-Si systems (Si/Fe 0-4, pH 3-10) was investigated by combining local scale spectroscopic methods (EXAFS, FTIR and NMR) and at the semi local scale (SAXS). The Fe clusters within the precipitates have two growth regimes depending on the Si/Fe ratio: the growth is three and two dimensional for Si/Fe fl and Si/Fe ≤ 1 respectively. The presence of Fe-O-Si bonds within the precipitated phases has been demonstrated. Their formation and relative proportion was found to be very dependent on the pH and Si concentration The size of silica domains within the precipitates was shown to increase with increasing Si/Fe and/or decreasing pH. The high fractal dimension (Df) of the aggregates is attributed to the presence of the SiO4 ligands, but the evolution of Df linearly depends on the polymerization state of iron.

LiNi1-yCoyO2 materials are particularly interesting as positive electrode in lithium-ion batteries. Their 7Li MAS NMR spectra are sensitive to the presence of paramagnetic Ni3+ cations as nearest and next-nearest neighbors. These contact shift (or Fermi contact) interactions are used to yield information on the lithium environment in terms of paramagnetic cations.

Electrochemically deintercalated LixNi0.30Co0.70O2 phases have been characterized by XRD, 7Li MAS NMR, electronic conductivity and thermoelectronic power. Ni3+ oxidation to Ni4+ occurs at the beginning of deintercalation, leading to a Ni3+/Ni4+ hopping which causes an exchange of the 7Li NMR signals of the Li ions interacting with nickel. For higher deintercalation amounts, the signal due to Li ions with only cobalt as first and second neighbor is also involved in the exchange upon heating, showing the onset of ionic hopping. For x close to 0.70, an increase of the NMR shift with temperature is observed, which is assigned to a hopping between Ni4+ and Co3+. Therefore, the question as to which ion is actually oxidized during deintercalation is somewhat irrelevant around this composition. Finally, for x < 0.70, the presence of Ni hinders a true long-range electronic delocalisation between Co4+/Co3+ (LS) as it happens in LixCoO2(x < 0.70). However, electrons are clearly delocalized in restricted zones, as seen from NMR and thermoelectronic power coefficient.

It has been known that some additives such as Nb2O5 are efficient quality factor compensators to potential additives for low-T sintering of (Zr0.8Sn0.2)TiO4such asZnO. The compensation mechanism of Nb2O5was analyzed in the light of its effects on the Zn incorporation in grains. ZST ceramics were prepared by conventional mixed oxide method and their microwave dielectric properties including quality factor, permittivity and temperature coefficient frequency (TCF) were measured at X-band. After sintering at 1350 and 1400oC, samples were post-annealed at 900∼1100oC. It was found that as Nb2O5 was added, the quality factor of 6 mol % ZnO-ZST specimens increased from 24000 to 44000 without any sacrificing of other dielectric properties such as permittivity and TCF. According to TEM and XRD, Nb addition tends to enhance Zn diffusion toward grain boundaries while Nb moved in the opposite direction. Due to the fact that no second phases were formed, it was assumed that the redistribution of Zn and Nb could play a major role in the enhancement mechanism of quality factor. Post-annealing can also be a secondary booster for the quality factor of ZST. After annealing at 900∼1100oC, the quality factor of a specimen with additives, increased again up to 48000 due to further decrease of oxygen vacancies resulting from further out-diffusion of Zn toward grain boundaries and incorporation of Nb into the grain.

Bulk physical properties of layered pnictide-oxides, Na2Ti2Pn2O (Pn = As, Sb) have been characterized. Both As and Sb compounds exhibit anomalous transitions in temperature dependent magnetic susceptibility and electrical resistivity. The powder neutron diffraction data show no superlattice reflections indicative of long-range order. The origin of the physical property anomalies and structure-property relationship between As and Sb compounds are described in terms of a charge-density-wave/spin-density-wave mechanism.

The construction of metal-anion arrays within Dion-Jacobson-type (DJ) perovskites was studied. A variety of hosts readily react with CuCl2 to produce compounds of the form (CuCl)[A'n-1(M,M')nO3n+1] (A' = alkaline earth, rare earth or Bi; M/M' = Nb, Ta, and/orTi; n = 2, 3). In contrast, CuBr2 only reacts with some of these hosts; this difference relative to the chloride may simply be a size effect. The formation of metal-anion arrays with other transition metals has also been examined. (FeCl)LaNb2O7 can be readily prepared from FeCl2, while reactions with FeBr2and NiCl2 under similar reaction conditions result in compounds of the formM0.5LaNb2O7 (M = Fe, Ni). The reductive intercalation of lithium and sodium into (CuCl)LaNb2O7 was also examined and was found to produce new compounds that have a large layer expansion.

Cd2Os2O7 crystallizes in the pyrochlore structure and undergoes a metal-insulator transition (MIT) near 226 K. Here we present resistivity, heat capacity, and magnetization results on Cd2Os2O7. Both single crystal and polycrystalline material were examined. We also present LAPW electronic structure calculations on Cd2Os2O7. We interpret the results in terms of a Slater transition. In this scenario, the MIT is produced by a doubling of the unit cell due to the establishment of antiferromagnetic order. A Slater transition--unlike a Mott transition--is predicted to be continuous, with a semiconducting energy gap opening much like a BCS gap as the material is cooled below TMIT.

Rhombohedral (R) phases of the binary systems AE-Bi-O (AE = Ca, Sr, Ba) have low temperature (β2) and high temperature (β1) polymorphs and the β1 polymorph is a good oxygen ion conductor. In a previous study, we showed that in the ternary system Ba-Sr-Bi-O, conductivities of polycrystalline R samples are unaffected by Ba:Sr, whereas temperature ranges of the β2↔β1 polymorphic transition are. Recently, we proved that the conductivity of both polycrystalline and single-crystal R samples is sensitive to spatial direction. For single crystals, the conductivity is highest perpendicular to the c-axis. Along the conduction plane, the conductivities are significantly higher than those of polycrystalline R samples; perpendicular to that plane they are significantly lower. The BaBiO3 perovskite (P) phase, predominantly an electronic conductor, has conductivities of 10 to 102 S/cm at 350-800°C in air. Conductivity measurements of the R-P assemblages with different R:P showed that percolation threshold is around 35 volume % P.

A fundamental study of the Li insertion behavior of a series of materials consisting of a TiO2 core having MoO3 on the surface has been carried out in order to determine the influence of the shell. These TiO2-(MoO3)z materials, where (z) denotes the fraction of coverage from a partial to a double layer, range in diameter from 40-100 Å. Calculations have been done on their theoretical lithium capacity using a maximum of Li0.5TiO2 for the core, and Li1.5MoO3 at the TiO2/MoO3 interface, and they have been compared to that found experimentally. The reversible Li-insertion capacity was shown to increase from 0.34 per Ti for the pure TiO2 sample, to 0.91 Li per transition metal when the MoO3 coverage increased to one monolayer. There was only one plateau observed in the electrochemical scans for the samples showing that they function as a single-phase material making them interesting for electrodes. The redox voltage of the TiO2/Li0.5TiO2 biphasic transformation increased 60 mV from the pure TiO2 to the sample containing one monolayer of MoO3. This effect was interpreted as due to a change in TiO2 surface charge coming from an inductive effect of Ti-O-Mo bonds.

LiCoO2 is an important cathode material for rechargeable batteries. Al substitution on Co sites was recently found to enhance its intercalation voltage. We have developed a reliable and less expensive method for the synthesis of such LiAlxCo1−xO2 compositions using simple salts of the constituent elements and organic solvents. X-ray diffraction and Raman spectroscopy were used for structural characterization of these materials at various annealing temperatures. The phase evolutions in LiAlxCo1−xO2 compositions were studied using micro-Raman spectroscopy and a phase diagram is proposed based on the observations. The phase diagram suggests that thin films of these materials can be deposited at substrate temperature at about 650°C

A series of three lead borosilicate glasses were synthesized and analyzed for structural information with both 11B and 207Pb solid-state nuclear magnetic resonance (NMR) spectroscopic methods. Results showed that increasing lead content caused lead to take a more active role in the network as a former and that the populations in these sites can be approximately quantified. 207Pb phase-adjusted-spinning sidebands (PASS), 11B magic-angle spinning (MAS), and 11B multiple-quantum MAS (MQMAS) experiments were used to determine structural parameters for the two nuclei. The 207Pb PASS experiment showed that at higher lead content, more covalent bonding was present. This principle was demonstrated in both an overall shift of the spectral resonances and a quantitative change in site ratios. The 11B MAS experiment showed that the ratio of BO3 to BO4 units was dependent on the amount of lead and boron, consistent with previous studies. Preliminary 11B MQMAS experiments failed to detect any BO3– units, previously hypothesized to exist in this system.

The Néel temperatures of Ba6Mn4MO15 (M = Cu, Zn) have been determined by neutron powder diffraction to be ∼ 6 K. In both cases, short-range magnetic coupling within the individual chains of this pseudo-1D crystal structure produces a susceptibility maximum at a temperature somewhat higher than that at which the frustrated interchain interactions establish long-range magnetic order.

Nanoparticles of CoFe2O4 in the size range of 5 nm to 36 nm have been synthesized by first producing two-line Co-doped ferrihydrite and annealing it at temperatures between 573 and 1073 K. Co-doped ferrihydrite is produced by reacting appropriate amounts of FeCl3/CoCl2 solutions with NH4OH at pH = 7. Thermogravimetric measurements provide evidence for the ferrihydrite to CoFe2O4 conversion between 500 and 700 K and x-ray diffraction is used to confirm the transformation to CoFeO4 and determine the particle size. The lattice constant increases initially with the increase in particle size approaching a constant value above 20 nm. The measured Tc equals 788 K for the 36 nm particles. Measurements of magnetization as a function of temperature and magnetic field confirm that the precursor Co-ferrihydrite is a superparamagnet with T ≃ 40 K, whereas for the 30 nm CoFe2O4, the coercivity Hc ≃ 7 kOe at 20 K, decreasing to Hc ≃ 800 Oe with Ms ≃ 60 emu/g at 300 K.