Solvothermal/hydrothermal reactions of 4, 4′-biphenyldicarboxylic acid (H2bpdc) and cobalt (II) salt with pyridine derivative ligands such as 3-methylpyridine (3-pic), 4-methylpyridine (4-pic), as well as a longer terminal ligand 4-benzylpyridine (4-bzpy) generated four new extended structures: 1D zigzag polymer chain 1 crystallized in C2/c with a formula [Co(bpdc)(3-pic)2]·(3-pic); 1D helical chain compound 2 crystallized in P41 with a formula [Co(bpdc)(4-pic)2], 2D non-interpenetrating network 3 crystallized in P2221 with a formula [Co(bpdc)(4-pic)2]·(4-pic)0.5·H2O, and 2D non-interpenetrating network 4 crystallized in P2/c, formulated as [Co(bpdc)(bzpy)2]. Our studies show that terminal ligands play an important role in affecting the dimensionality and topology of the structures formed. Magnetic susceptibility and isothermal magnetization results revealed an antiferromagnetic ground state for 3 with a transition temperature T = 4.7 K, and paramagnetic behavior at high temperature range for 1 and 2.

Barium strontium titanate (Ba0.7Sr0.3TiO3, BST) ceramics prepared by a reaction-sintering process were investigated. The mixture of raw materials of stoichiometric Ba0.7Sr0.3TiO3 was pressed and sintered into ceramics without any calcination stage involved. Perovskite BST ceramics were obtained after sintered at 1330–1370°C for 2–6 h. For 6 h soak time, a density value 5.68g/cm3 (99.8% of the theoretic value) was obtained at 1350°C sintering. Grains of sizes between 2μm and 15μm were formed after 1330–1370°C sintering for 2–6 h. A diffused ferroelectric-paraelectric transition was observed in pellets sintered at 1330°C for 2 h and disappeared at a longer soak time or a higher sintering temperature.

SrBi2Ta2O9 (SBT) samples have been prepared by sol-gel technique with varying amount of excess Bi added to the starting composition. The excess Bi profoundly affects the dielectric and ferroelectric properties. The dielectric constant (ε) and remnant polarization increases from 80 and 1.4 μ C/cm2 for SBT with 1 mole % of excess Bi to 120 and 6.5 μ C/cm2 for SBT with 20 mole % of excess Bi. The Raman spectra, scanning electron microscopy images and the x-ray diffraction analysis show an improvement in structural quality of the samples with addition of excess Bi to the starting composition. The effect of Mn doping has also been studied by preparing SrBi2Ta2-x Mnx O9 (SBT-Mn) with x = 0 – 0.1. In the case of SBT-Mn samples, the XRD spectra revealed an unknown phase when x > 0.025. However, Raman spectra reveal the retention of Bi layer structure for all Mn compositions, with possibly small distortions. With Mn addition, ε increased to ∼ 140 for x < 0.005, but decreased to ≤ 120 when x > 0.015. The value of ε is independent of frequency from 60 to 85 kHz for all compositions of Mn. The effect of Mn addition resulted in a strong decrease in the area of the hysteresis loops.

The solution phase synthesis of narrow diameter CdSe and PbSe nanowires (NWs) is described. Crystalline NWs with lengths between 1–10 μm are obtained using a seeded solution approach, whereby NW growth is catalyzed by Au/Bi core/shell nanoparticles (NPs). A gold biphasic reduction step results in 1.5 (3) nm diameter Au NPs and is followed by the thermolysis of trialkylbismuthines to yield low melting, bimetallic particles with diameters less than 3 nm. These Au/Bi NPs are catalytically active towards the growth of similar diameter CdSe NWs (∼7 nm) that exhibit quantum confinement effects. By varying the ratio of Cd (or Pb) to Se, both straight and branched NWs can be obtained, with branched structures including v-shapes, tripods, and y-shapes in the case of CdSe and t-shapes in the case of PbSe. Structural characterization shows that both straight and branched CdSe NWs grow along either the <111> zinc blende (ZB) or <0001> wurtzite (W) directions. Conversely, PbSe has a rocksalt crystal structure, and both straight and branched NWs grow along <100> directions.

Single crystals of two new compounds, Eu3InP3 and Eu3In2P4, were prepared by In flux synthesis. Eu3InP3 crystallizes in the Pnma orthorhombic space group with a = 12.6517(15) Å, b = 4.2683(5) Å, c = 13.5643(14) Å, and Z = 4 while Eu3In2P4 belongs to Pnnm space group, a = 6.6999(6) Å, b = 16.1019(13) Å, c = 4.2725(4) Å, and Z = 2. These two compounds are isotypic to the main group compounds Sr3InP3 and Sr3In2P4 respectively. Both structures consist of distorted In-P tetrahedra and isolated Eu2+ ions. In Eu3InP3 these tetrahedra share corners to form one-dimensional chains. The Eu2+ ions occupy three different sites, and form a complicated network containing some triangles. In Eu3In2P4 these tetrahedra form edge-shared dimers, and these dimers form chains. Eu3InP3 shows unusual magnetic properties: there are three magnetic ordering transitions at 14 K, 10.4 K, and around 5 K and the magnetization curve shows steps in the low temperature region. Eu3In2P4 magnetically orders at 14.5 K. Its magnetization curve saturates at around 1T. Eu3InP3 and Eu3In2P4 are both semiconductors.

The chemically controlled polyol process, with TMAH and water as OH- donors in the nickel hydroxyglycolate intermediate phase, prepares the nickel nano particles. The water additive acts as the OH- donor and enhances the solubility of salt in polyol for efficient production and monodispersive particles. Water and TMAH, selected to decrease the contamination of alkali metal from inorganic base, as OH- donors control the intermediary solid phase as a reservoir for Ni2+ species. The particle is about 80 nm with a faceted shape when the reaction is controlled by a combination of TMAH and water,. The nucleating agent is powerful to decrease the particle size, but in this basic reaction condition, it is not effective enough to get a small size.

Synthesis of (Pb0.45Ca0.55)(Fe0.5Nb0.5)1-yTiyO3 (y=0 and 0.1; PCFN and PCFNT) ceramics by a reaction-sintering process was investigated. The mixture of raw materials was pressed and sintered into ceramics without any calcination stage involved. The density 5.88g/cm3 (91.6% of the theoretical value) is reached at 1270°C for 2 h soak time in PCFN. Densification increased as B-site was substituted by 10% Ti and a density value 6.21g/cm3 (98.1% of theoretical value) was obtained after 2 h sintering at 1270°C. Grains are of 4.6–19.3μm in PCFN and 2.5–16.5μm in PCFNT at 1150–1270°C. Grain growth was retarded as the B-site was substituted by 10% Ti in PCFN ceramics.

TiO2 thin films (500 – 1000 nm in thickness) were deposited using pulsed DC magnetron reactive sputtering, on glass substrates. The depositions used a Ti source in an Ar+O2 gas mixture with different parameters of power (350 - 500W), substrate temperature (no additional heat - 400°C), growth pressure (3.0 - 5.0 mTorr) and oxygen gas flow rate (6.0 - 8.0 sccm). The x-ray diffractions (XRD) show amorphous and/or anatase phases depending on the deposition conditions. The films were found to be amorphous at lower substrate temperature and at lower powers. The sample with 4 mTorr, 400W of power, a substrate temperature of 250 C with 7.0 sccm of oxygen flow has the best crystalline quality. The temperature dependent electrical conductivity measurement in air for the above films shows an exponential increase in conductivity with temperature.

Vanadium oxide nanotube dispersions were investigated in water suspensions and characterized by TEM, absorption spectroscopy and optical limiting testing. The results show that the nanotubes are unrolled and oxidized after 6-day aging, resulting in some change of optical limiting property at the two wavelengths (532 and 1064 nm). The 1.27-eV absorption band is assigned as a superposition of both V d→d and V4+→V5+ charge-transfer excitations, and the features at 2.9 eV are attributed to O 2p→V 3d charge-transfer excitations.

InSb has a large carrier mobility and a high sensitivity in the infrared wavelength range (3–5 μm), which makes it a good quantum dot material for infrared (IR) detectors. In this study, the synthesis of the nanocrystalline III-V semiconductor indium antimonide (InSb) by solvothermal reduction methods was investigated. InSb was synthesized by using indium (III) chloride and antimony (III) chloride as the starting materials and sodium borohydride as the reducing agent. Pure-phase InSb was successfully produced with diethylenetriamine and tetraethylenepentamine as the solvents and a Schlenk line apparatus as the reaction vessel. X-ray diffraction (XRD) was used to verify the successful production of InSb and transmission electron microscopy (TEM) was used to determine the particle size and shape of the product. In the future, growth kinetics of the particles will be investigated as they relate to their spectroscopic quantum confinement effects.

Various cations (Li+, Na+, K+, NH4+, Cs+, Mg2+, Ca2+, Ba2+) were introduced during the formation of a V2O5. nH2O gel. Cation intercalated Xy V2O5. nH2O (y = 0.3 for X = Li+, Na+, K+, NH4+ or y = 0.15 for Mg2+, Ca2+, Ba2+) were first obtained at room temperature but some of them evolve upon ageing into a new phase: XV3O8. nH2O for X = Na+, K+, NH4+ and Cs+ or XV6O16. nH2O for X = Mg2+, Ca2+, Ba2+. All the vanadium oxide phases were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR); the supernatant solutions were analysed by 51V NMR spectroscopy. These vanadium oxide phases exhibit a layered structure with cations and water molecules intercalated within the interlayer space. The formation of the different phases depends mainly on the pH of the supernatant solution and on the nature of the cation.

Materials with the K2NiF4 structure and a magnetic atom on the B site are examples of a pseudo-2D square lattice. The nearest neighbour interactions are very strong and, with iron(III), usually lead to xy antiferromagnetic coupling. We have used powder neutron diffraction at 2 K to study the magnetic structures of A2FeO3X where A is Ca or Sr and X is Cl or Br. There are two common magnetic structures for K2NiF4-type xy antiferromagnets, those of La2NiO4 and La2CuO4, here we find the latter. In Sr2FeO3F we find a more complex situation. The reflections corresponding to the La2CuO4 magnetic structure are present from 2 K to ambient temperature, but a further set of peaks decays from 2 K to around 60 K. These correspond to a magnetic structure with a doubled c-axis. This is due to a magnetic structure in which La2NiO4-and La2CuO4-type stacking alternate. To our knowledge this is the only example of this magnetic structure type.

Boron fibers made by a commercial chemical vapor deposition (CVD) process have been used as precursors for the formation of magnesium diboride (MgB2) superconducting wires. Prior to a reaction with magnesium, the addition of dopants such as carbon and titanium to the boron fiber has been shown to enhance the superconducting properties of MgB2. These dopants also influence the kinetics of the reaction with magnesium. In this study, the effect of carbon dopant additions on the microstructure of boron fibers was investigated using powder x-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Additionally, bundles of boron fibers were pressure infiltrated with molten magnesium and reacted at elevated temperatures. The microstructure and microchemistry of the fiber-metal interfaces were investigated by TEM and energy dispersive x-ray analysis (EDS).

Superconductor films of the BSCCO system have been grown by dip coating technique with good success. The chemical method allows us to grow high temperature superconductor thin films to get better control of stoichiometry, large areas and is cheaper than other methods. There is a great technological interest in growth oriented superconductor films due anisotropic characteristics of superconductor materials of high critical temperature, specifically the cuprates, as we know that the orientation may increase the electrical transport properties. Based on this, the polymeric precursor method has been used to obtain thin films of the BSCCO system. In this work we have applied that method together with the deposition technique known as dip coating to obtain Bi-based superconductor thin films, specifically, Bi1.6Pb0.4Sr2.0Ca2.0Cu3.0Ox+δ, also known as 2223 phase with a critical temperature around 110 K. The films with multilayers have been grown on crystalline substrates of LaAlO3 and orientated (100) after being heat treated around 790°C - 820°C in lapse time of 1 hour in a controlled atmosphere. XRD measurements have shown the presence of a crystalline phase 2212 with a critical temperature around 85 K with (001) orientation, as well as a small fraction of 2223 phase. SEM has shown a low uniformity and some cracks that maybe related to the applied heat treatment. WDS has also been used to study the films composition. Different heat treatments have been used with the aim to increase the percentage of 2223 phase. Measurements of resistivity confirmed the presence of at least two crystalline phases, 2212 and 2223, with Tc around 85 K and 110 K, respectively.

The mixed metal oxides having layered crystal structure have been of much interest because of their various new and excellent functions. Precise phase diagrams on the oxygen content have not been clarified for most of these layered oxides, while oxygen nonstoichiometry often plays a crucial role for determining functions of oxide materials. In this paper, we report oxygen nonstoichiometry and related physical properties mainly on the manganese-based and cobalt-based layered oxides. In the La2–2xSr1+2xMn2Oy (x = 0.3, 0.4), dramatic change in magnetization properties with oxygen content were observed in spite of its small oxygen nonstoichiometry. For (Ca2CoO3-δ)0.62CoO2 systems, high valence metal substitution was found to be effective for suppression of oxygen nonstoichiometry, increase of decomposition temperature and thermoelectric properties.

We report the pressure dependence of the thermoelectric power of As2Te3. Pressures up to 10 GPa were induced using a Mao-Bell diamond anvil cell. The absolute value of the thermoelectric power dropped from S ≈ 230μV/K at ambient pressure to S ≈ 75 GPa near 5 GPa. At 6 GPa it then increased rapidly to S ≈ 220βV/K. This behavior is indicative of a structural phase transition as suggested by previously published high pressure phase diagrams.

Spent fuel reprocessing by an innovative reductive extraction process in a molten fluoride medium (LiF/AlF3) is now being evaluated; in this hypothesis, all the unrecoverable fission products would be conditioned as fluorides. A preliminary study was undertaken to assess the feasibility of incorporating these fluorides by melting in a glass-ceramic matrix. The containment matrix for the fluorinated waste stream was selected after examining the consequences of fluorinated compounds on the vitreous state and on the physical and chemical properties of the melt and the solidified glass. The presence of fluorinated compounds in the raw materials used to produce the vitreous material raises the problem of the volatility of some fluorides, of their solubility in the melt, and of possible crystallization of the material.

As has been discussed, research on the electronic structure between organic and inorganic atoms in hybrid compounds has become important. In our study, DV—Xα method was employed to calculate the electronic structure of the hybrid compound. The information obtained from the calculation included orbit charge, bonding order, Fermi energy, density of the state, etc. The influence of organic and inorganic parts on the energy band structure of the hybrid compound was discussed based on the calculation results of Fermi energy and density of state. The chemical bonding between organic and inorganic parts in the hybrid compound was also analyzed in detail according to the orbital charges and bond orders.

Liquid and amorphous metallic systems have proven difficult to model. Some efforts have relied on the use of parameterized classical potentials of the Lennard-Jones type or geometric hard sphere simulations, but first principles approaches have been rarely used. Clearly a knowledge of atomic structures is paramount for calculating physical properties. In this work we apply our recently developed ab initio DFT approach (A. A. Valladares et al., Eur. Phys. J. 22 (2001) 443) for the generation of amorphous semiconducting materials, to amorphize aluminum and an aluminum-nitrogen alloy. We report radial distribution functions (RDFs) and specific atomic structures of periodic amorphous/liquid cubic supercells of 108 atoms with a volume of (12.1485 Å)3, generated using the Harris functional.

Mesoporous silica powders have been synthesized starting from aqueous solutions of Si(OCH2CH3)4 (TEOS) under acidic conditions, using non-ionic alkyl poly(ethylene oxide) oligomer (Brij76) as a structure-directing agent. Template removal was performed by thermal treatment in air as well as by ethanol extraction. The annealing process (400 - 600°C) resulted in more efficient elimination of the organic molecules, thus yielding hexagonal (p6mm) mesopor-ous materials with pore volume and specific surface area ranging between 0.58 – 0.41 cm3/g and 900 – 700 m2/g, respectively. The systems were characterized by X-Ray Diffraction (XRD), N2 BET adsorption, Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Particular attention was focused on the evolution of the system mesostructural and porous features as a function of the template removal procedure. The obtained mesoporous networks are suitable as matrices for the development of nanocomposite systems in which the dispersion or the growth of various guest species (clusters, molecules…) can be addressed into the host mesopores.