The correlation between 31P and 23Na (or 133Cs) nuclei in a mixed-alkali phosphate glass has been investigated by TRAnsfer of Populations by DOuble Resonance (TRAPDOR) NMR spectroscopy. The variation in spatial proximity between 31P nuclei in phosphate tetrahedra and sodium (or cesium) modifier ions has been demonstrated in a phosphate glass with molar composition 25 Cs2O: 31 Na2O: 44P2O5. Interactions between 31P and 23Na (or 133Cs) nuclei are shown to exist even at low dephasing times indicating the short-range nature of these couplings. The ratios of resonance intensities from Q1 and Q2 phosphate units show different trends depending on whether couplings to 23Na or 133Cs are investigated, demonstrating the differing structural roles of the modifier alkali cations within the glass.

Magnetic force microscopy (MFM) and atomic force microscopy (AFM) were used to investigate the surface topography and micromagnetic structure of La0.83Sr0.13MnO2.98 single crystals with colossal magnetoresistance (CMR). The crystals were grown by fused salt electrolysis and characterized by chemical analysis, X-ray diffraction, magnetic and transport measurements. The crystals are rhombohedral (R 3 c). Magnetic and transport measurements indicate that the ferromagnetic ordering at 310 K is associated with an insulator-metal transition at the same temperature. A maximum negative magnetoresistance (-62 %) is observed at 290 K in an applied magnetic field of 5 T. The magnetoresistance increases in magnitude sharply (1.8 %), comparing to the rest of the change, with increasing magnetic field up to 20 G, and then it increases slowly with increasing field.

MFM and AFM were used to study the (110) surface as well as a number of unspecified surfaces. Surface topography of an as-grown crystal exhibits well-developed surface corrugations due to extensive twinning. The corrugation angle at twin boundaries can be related to the unit cell parameters, surface and twinning planes. Magnetic force microscopy images show that magnetic domain boundaries are pinned to the crystallographic twins; a small number of unpinned boundaries are observed. The statistical analysis of domain boundary angle distribution is consistent with cubic magnetocrystalline anisotropy with easy axis along [100] directions for this material. Unusual magnetization behavior in the vicinity of topological defects on the surface is also reported. MFM contrast was found to disappear above the ferromagnetic Curie temperature; after cooling a new magnetic structure comprised of Bloch walls of opposite chiralities developed.

A protonated form of a layered perovskite was prepared from an Aurivillius phase Bi2SrNaNb3O12via acid treatments, and the effect of the type of mineral acids was investigated. The treatment with HX (X = Cl, Br, I) resulted in the formation of a protonated form H1.8[Sr0.8Bi0.2NaNb3O10], while no reactions were observed for HNO3 and H2SO4 under the present experimental conditions. All the products obtained by HX-treatments exhibited layered structures and the structures of the perovskite-like slabs were preserved.

PbZrO3 undergoes a phase transition to a paraelectric phase at 230°C. During this phase transition the unit cell changes from orthorhombic to cubic. Structural changes of PbZrO3 have been monitored using solid state NMR by measuring the variation in the 207Pb chemical shielding tensor as a function of temperature. The two distinct lead sites show rather different behavior as a function of temperature. The less shielded lead maintains an almost constant asymmetry parameter η = 0.2 from 0°C to 200°C while the more shielded lead resonance becomes more axially symmetric as the temperature is raised going from η = 0.24 at 0°C to [.eta] = 0.08 at 200°C. Powder pattern singularities become less distinct near the phase transitions, but the temperature dependence of the chemical shift tensor principal values remains continuous, and there is no evidence of an intervening higher-symmetry phase. At the phase transition, both resonances collapse into a single narrow line characteristic of a nucleus at a high-symmetry site. Results of a preliminary study of the PbZr1−xTixO3 solid solutions by 207Pb solid state NMR are also presented.

The one-dimensional 1×1 and 1×2 tunnel structures of manganese dioxides, pyrolusit(β-MnO2) and ramsdellite (R-MnO2), respectively, were chemically intercalated with LiI. Two 7Li resonances were observed in lithiated pyrolusite. One isotropic resonance arising at 110 ppm shows a short spin-lattice relaxation time (T1 ∼ 3 ms) and was assigned to Li+ ions in the 1×1 tunnel structure. The other isotropic resonance arising at 4 ppm shows a long spin-lattice relaxation time (T1 ∼ 100 ms) and was assigned to Li+ ions in diamagnetic local environments in the form of impurities such as Li2O or on the surface of the MnO2 particles. Three 7Li resonances were observed in lithiated ramsdellite at very different frequencies (600, 110 and 0 ppm). The resonance at 600 ppm, which is observed at low lithium intercalation levels, is assigned toLi+ ions coordinated to both Mn(III) and Mn(IV) ions in the 1×2 tunnels, while the resonanceat 110 ppm is due to Li+ ions coordinated to Mn(III) ions and appears at higher Li levels. The resonance at 0 ppm is associated with a long spin-lattice relaxation time (T1 ∼ 100 ms) and is also assignedto Li+ ions in diamagnetic impurities.

The lithium ion conducting properties of materials of composition La0.58Li0.26TiO3, Nd0.58Li0.26TiO3, La0.67Li0.25Ti0.75Al0.25O3 and La0.29Li0.12NbO3 have been compared in relation with their microstructure. All the oxides have powder X-ray diffraction patterns characteristic of a perovskite-related structure with lattice parameters a∼√2ap, b∼√2ap, c∼2ap (p refers to cubic perovskite). However, some important differences are observed in their microstructure by SAED and HRTEM. Ordering between vacancies, Li+ and La3+ or Nd3+ and twinning of the NbO6 or TiO6 octahedra tilting system are shown in La0.29Li0.12NbO3 and Nd0.58Li0.26TiO3, which are the materials having a lower ionic conductivity. The La0.58Li0.26TiO3 and La0.67Li0.25Ti0.75Al0.25O3 oxides do not show ordering between cations.

Highly porous ruthenium oxide films were prepared using ruthenium ethoxide solution at low temperatures. The specific capacitance of the ruthenium oxide film electrode made with ruthenium ethoxide solution is much higher than that made using the traditional ruthenium chloride solution. It was found that amorphous ruthenium oxide films with high porosity could be formed at temperatures of 100-200 °C. At temperatures above 250 °C, crystalline ruthenium oxide films were formed. Electrochemical capacitors were made with ruthenium oxide film electrodes and were tested under constant current charging and discharging. The maximum specific capacitance of 593 F/g was obtained from the electrode prepared at 200 °C. The interfacial capacitance increased linearly with increasing film thickness. A value of interfacial capacitance as high as 4 F/cm2 was obtained from the electrode prepared at 200 °C.

Electrical conductivity experiments on NiS2−xSex (x = 0.45) subjected to moderate pressure in the 30 – 800 mK range permit the investigation of quantum critical phenomena in this system. Detailed data are presented in the context of standard theories of correlation effects in the vicinity of a critical point. The critical exponents pertaining to these effects have been evaluated; the significance of these findings require further study.

Magnetite is a classic example of a mixed-valent transition metal oxide, in which electronic conductivity and ferromagnetism result from electron hopping between octahedrally coordinated Fe2+ and Fe3+ states. Below the 122 K Verwey transition, the conductivity falls by a factor of ∼100 and a complex monoclinic (or triclinic) superstructure of the high temperature cubic spinel arrangement is adopted. This is assumed to be the result of Fe2+/Fe3+ charge ordering on the octahedral sites, but this has not been confirmed crystallographically, as single crystal refinements have been hampered by the extensive twinning that accompanies the Verwey transition. We have used very highly resolved powder diffraction data to attempt Rietveld refinements of the low temperature structure. The powder sample was prepared by grinding a single crystal of stoichiometric magnetite. Data were collected at 90 K on instruments HRPD at the ISIS neutron source, UK, and BM16 at the European Synchrotron Radiation Facility, France. The very high resolution of these data enables the monoclinic distortion to be observed, and the structure has been refined on the supercell proposed by Iizumi et al (Acta Cryst. B38, 2121 (1982)) with Pmca pseudosymmetry, giving parameters a = 5.94443(1), b = 5.92470(2), c = 16.77518(4) Å, β = 90.236(1)°. The mean octahedral site Fe-O distances differ from each other significantly, but the maximum difference between values is only 20% of that expected for ideal Fe2+/Fe3+ charge ordering.

Using first principles techniques we have examined the relative physisorption/chemisorption energetics of neutral molecular water and oxygen at the most thermodynamically stable surface (110) of tin dioxide. We find that water binds more strongly to the perfect surface at 5 co- ordinate tin sites than oxygen. However, binding of both water and oxygen at bridging oxygen vacancies in the defective surface is comparable. In the context of gas-sensing behaviour at moderate temperatures (∼300K), we propose that the Mars and van Krevelen [1] re-oxidation reaction will slow when the partial pressure of water is high, since the number of favourable adsorption sites will effectively decrease. In addition, one would expect that the surface conductivity will increase, since the re-oxidation reaction will be hindered.

Mesostructured cerium(IV) oxides were directly synthesized via the hexamethylenetetramine (HMT) homogeneous precipitation method. Cerium(III) nitrate, a templating agent, HMT and water were mixed in a molar ratio of 1: 0.1-2: 1-15: 100-1000 and kept at 65 to 95°C for 10 to 40 hours. 1-Hexadecanesulfonic acid sodium salt was used as the templating agent. Low-angle XRD patterns showed that the as-prepared powders had a lamellar structure with d100=4.1 nm. Wide-range (2θ=10-70°) XRD patterns also exhibited reflection peaks of CeO2 with a fluorite structure. However, the low-angle reflection peaks disappeared in calcined specimens.

The bombardment of C with 100 keV and 1 MeV W at normal incidence is studied as a function of the incident W fluence experimentally and by computer simulation with the program TRIDYN. Calculated oscillations in the amount of retained W and in the target weight change are confirmed experimentally for 100 keV at room temperature. XPS investigations show W2C formation during ion implantation already at room temperature. RBS depth profiles for 1 MeV bombardment show W mobility and surface segregation even at liquid nitrogen (LN2) temperatures. At elevated temperatures W clusters to form nano-particles at the surface and the oscillations in the retained amount of W disappear.

Thin films of NdNiO3 were grown using pulsed laser deposition on single crystal substrates of [100]-oriented LaAlO3 and SrTiO3. X-ray diffraction and reflectivity, scanning electron microscopy, and atomic force microscopy were used to characterize the chemical, morphological and structural traits of the thin films. Single-phase epitaxial films are grown on LaAlO3 and SrTiO3 at 625°C in an oxygen pressure of 200 mTorr. At higher temperatures, the films partially decompose to Nd2NiO4 and NiO. The films are epitaxial with the (101) planes (orthorhombic Pnma notation) parallel to the substrate surface. Four in-plane orientational variants exist that correspond to the four 90° degenerate orientations of the film's [010] with respect to the in-plane substrate directions. Films are observed to be strained in accordance with the structural mismatch to the underlying substrate, and this leads, in the thinnest films on LaAlO3, to an apparent monoclinic distortion to the unit cell.

The La2−xSrxCuO4 phase diagram is interpreted within the framework of a transition from localized to itinerant electronic behavior. In the underdoped region 0 < x < 0.1, holes in the x2 – y2 band are not small polarons; each occupies a mobile correlation bag of 5 to 6 copper centers at temperatures T > TF, a spinodal phase segregation into the parent antiferromagnetic phase and a polaron liquid is accomplished below TF by cooperative oxygen displacements. In the overdoped compositions > x > 0.25, holes are excluded from strong-correlation fluctuations within a Fermi liquid. In the intermediate range 0.1 < x < 0.25, the polaron liquid formed below room temperature changes character with increasing x and decreasing T. In the polaron liquid, mobile two-hole bags of four copper centers order with decreasing temperature into alternate CuO-Cu rows of a superconductive CuO2 sheet at a critical composition xc ≍ 1/6. It is argued that hybridization of itinerant electrons with optical-mode phonons propagating along the Cu-O-Cu rows produces heavy electrons responsible for high-temperature superconductivity.

Hybrid inorganic/organic materials with open-framework or layered structures are known for many transition metals linked by functionalized organic molecules such as organic diphosphonates, polycarboxylates, polynitriles, etc., species with more than one equivalent functional groups. We have studied the effect of pH on such a system of cobaltmethylenediphosphonate and report three new compounds, Na3Co[(O3PCH2PO3)(OH)],Na2Co(O3PCH2PO3)•H2O, and Co2[(O3PCH2PO3)(H2O)], that form at very basic, moderately basic, and acidic conditions, respectively. More interestingstructural chemistry should be expected from linkers with two or more different functionalities. Both the carboxylic and phosphonic groups in carboxyethylphosphonic acid are used to coordinate to cobalt or calcium atoms in the new compounds Co3(O3PCH2CH2COO)2•6H2O and Ca(O3PCH2CH2COOH)•H2O. Taking one more step further in complexity we have also studied linkers with three different functional groups, phosphonated amino acids. The structures of two new compounds, Zn(O3PCH2CH(NH3)COO) and Zn(O3PCH2CH2CH(NH3)COO), are threedimensional frameworks made of zinccoordinated by both the carboxylic and phosphonic ends of the organic molecules. The amino groups are protonated and terminal in the voids of the frameworks.

We have investigated the electronic and magnetic properties of (Nd1−ySmy)0.45Sr0.55MnO3(0≤y≤1) crystals, in which one-electron bandwidth (W ) is systematically decreased from the parent compound (y=0) with increase of y. We have found remarkable magnetic phase transition concerning the change of rare-earth (RE) moments in low temperatures below 25 K. The subtle drop in resistivity superimposed upon the spin-valve like magnetoresistance (MR) was observed for the isothermal MR measurements, e.g. δρ(H)|ρ(H')≍4.7% at 3.5 T and 4 K. The phase transition fields corresponding to these concomitant magnetic and resistive changes monotonically decrease with temperature and disappear above ∼25 K. It turned out that the resistive drop is due to the field-induced increase of magnetic moments ofRE ions from magnetization measurements. The field-induced phase transition from the small moment state to the large one in RE ions can be explained in terms of energy level crossing between the crystal-field-split J multiplets by the Zeeman effect.

Solid solutions of LaMxFe1−xO3 (with M = Ni and Co) have been used in the Fischer- Tropsch reaction (CO + H2 → Hydrocarbons + CO2) and in the partial oxidation of methane (CH4 + 1/2 O2 → CO + 2 H2). In both catalytic reactions, the active catalyst is reported to be reduced metal particles; their size and their interactions with the support induce large differences in the product distribution.

In the nickel system, after total reduction by TPR all catalysts exhibit ferromagnetic behavior at room temperature. In situ magnetization in 1 Tesla on cooling the sample under reducing atmosphere shows one magnetic transition for each sample indicating one Curie temperature. These Curie temperatures are in between those known for bulk nickel and iron and decrease with the initial nickel content of the perovskite. This indicates that nickel is reduced first and induces the reduction of iron, leading to the formation of an alloy.

In the cobalt system, in situ magnetization on heating the sample shows a sharp increase of the magnetization only for x = 0.25, 0.40 and 1, corresponding to the formation of metallic cobalt nanoparticles. All other materials present only one increase of the magnetization for temperatures similar to those observed for the second reduction in TPR corresponding to the formation of CoFe alloys.

This research focuses on the design of chemically functionalized optical waveguide sensors. The waveguide is an optically transparent sol-gel coated onto a glass substrate chip. By having a higher refractive index than the substrate, the waveguide internally reflects a laser beam to photodetectors at both ends of the chip. The adsorption of any species onto the waveguide surface changes the light propagation, and therefore its effective refractive index, N. The change in N is dependent upon the amount of analyte present. By covalently bonding specific chemical receptors onto its surface, it can be designed to target a particular analyte. This research involves functionalizing the surface of the waveguide with ED3A in order to complex out of solution Ni2+. The change in N and the thickness of the adlayer will allow the concentration to be determined.

Bi, Y, and Al-doped antimonic acids with the empirical formula (1-x)Sb2O5·xM2O3·nH2O (M =Al, Bi and Y; 0 ≤ x ≤ 1) have been prepared by the direct reaction of an aqueous H2O2 solution with metal alkoxides. The electrical properties have been investigated by ac and dc conductivity measurements using a polycrystalline compactdisc as a sample, in connection with the water adsorption behavior. The (1-x)Sb2O5·xM2O3·nH2O (M = Bi and Y) materials exhibit a solid solution of cubic antimonic acid (Sb2O5·nH2O) with Bi2O3 and Y2O3 in the range of x = 0 – 0.1, and the ionic transference numbers of the materials are all over 0.98. The proton conductivity of (1-x)Sb2O5·xM2O3·nH2O (M = Bi and Y; x = 0.1) at room temperature increases to over 10-3 Scm-1 with an increase in the relative humidity. The conductivity is closely affected by the water adsorption behavior, which seems to be related to the introduction of oxygen vacancies.

Magnetic Compton profiles (MCPs) of a DyCo5.4 single crystal were measured at 10 K, 200 K and 300 K. The temperature dependence of the spin moment, which is deduced from the areas under the normalized MCPs, is significantly different from that of the total magnetization measured by a superconducting quantum interference device (SQUID). This difference is due to the presence of a substantial amount of the orbital moment on a Dy site that does not contribute to the magnetic Compton scattering cross section. The analysis of the MCPs reveals that the absolute value of the spin moment increases with increasing temperature and that the spin magnetic moment of the conduction electrons has an opposite sign to the total spin magnetization in the covered range of temperature.