We present a general approach to predict new inorganic solid compounds as a function of pressure, composition and temperature. Our method is based on the global exploration of the energy and enthalpy landscapes of the chemical system, followed by the construction of the corresponding free energy/enthalpy landcsapes.

We describe the Tl2SnAs2Q6, (Q= S, Se) compounds which consist of [SnAs2S6]2- layers with the Tl+ cations lying in between. Tl2SnAs2S6 and Tl2SnAs2Se6 crystallize in the space group P-3 with a = 6.706(4) Å, c = 7.187(6) Å and a = 6.996(3) Å, c = 7.232(4) Å respectively. These compounds are semiconductors with band gaps of 1.68 eV for the sulfide and 1.08 eV for selenide corresponding to their dark red and black colors respectively. Band structure calculations suggest indirect band gaps in these materials.

In the present study, hole carrier doping was attempted for CoSr2YCu2O7+δ which is a relating compound to a well known superconductor YBa2Cu3O7-δ by introduction of excess oxygen into CoO1+δ layer and cation substitutions. High valence metal substitution for cobalt and barium substitution for strontium were revealed to be able to introduce excess oxygen and generate hole carriers. Additional calcium substitution for yttrium enhanced hole carrier concentration p/Cu > 0.05 which was enough for superconductivity, however superconducting transition was not observed. This is possibly due to incorporation of cobalt in the CuO2 planes.

Electrostatic spinning is a well-developed technique for the fabrication of fibers in the nanoscale domain. Novel boron carbide nanofibers were generated by the electrostatic spinning and ceramic conversion of poly(norbornenyldecaborane) (PND) - a polymeric ceramic precursor. The prepyrolyzed fibers were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The ceramic fibers were characterized by SEM, X-ray diffraction (XRD), 11B magic-angle spinning nuclear magnetic resonance (MAS NMR) and DRIFT spectroscopy. SEM analysis showed retention of the nanostructure in the pre- and postpyrolyzed fibers.

We have prepared a soluble manganese alkoxide, and used in the first all-alkoxide synthesis of Ca, Sr, and Ba substituted lanthanum manganites. The phase development from gel to target oxide was monitored by TGA, DSC, powder-XRD, FT–IR spectroscopy, and TEM-EDS. Here we present the effect of dopant on the phase development. It was found that the dopants influence the temperature of complete oxide formation (≥650°C). The main difference in phase evolution was seen in the 300–600°C range, where the formation of crystalline phases in trace quantities seemed to temporarily reduce the elemental homogeneity.

The development of solution based synthesis approaches for preparing nanocrystals of III-V semiconductor presents a significant & important challenge especially with relation to shape control to achieve rod growth. To this end, a novel approach for synthesis of soluble semiconductor quantum rods using metal nanoparticles to direct and catalyze one-dimensional growth is developed. The synthesis method is useful in particular for III-V semiconductor with cubic lattice, where the utilization of surfactant-controlled rod-growth is not easily realized. The growth takes place via the solution–liquid–solid (SLS) mechanism where proper precursors are injected into a coordinating solvent as we reported in earlier work for InAs nanorods. Herein, we report the synthesis of high quality InP nanorods using Indium Acetate and myristic acid with gold nanoparticles as the catalysts in the SLS growth mode. A similar route was successfully developed for the growth of InAs nanorods. We find that the amount of Au catalyst in the reaction is an important parameter to achieving shape control. Transmission electron microscope (TEM) images of InP and InAs nanocrystals revealed that the crystals are mostly rod-shaped. XRD measurements, absorption spectra were preformed for the nanorods characterization.

This work presents results of investigation of the charge and coordination state of Fe cations in La1-xMexFeO3-y perovskites prepared by mechanochemical route by using MÖssbauer spectroscopy as related to bulk oxygen reactivity in H2 or in CH4 temperature-programmed reduction (TPR).

The synthesis of three layer sodium cobalt oxide, NaxCoO2 (x=0.3, 0.5, 0.6, 0.75 and 1.0) is reported. For x=0.6, 0.75, and 1.0, conventional solid-state synthesis was employed. x=0.3 and 0.5 were obtained via oxidative deintercalation of sodium at room temperature. x=0.3 can be hydrated to Na0.3CoO2•1.3H2O which is superconducting with a Tc of 4.3 K. Although having the same chemical stiochiometry as the previously reported two layer superconductor, it has a different stacking sequence of CoO2 layers making it structurally distinct. Crystals of three layer NaCoO2 show triangular morphology compared to hexagonal morphology for two layer Na0.7CoO2.

Formation mechanisms of perovskite Pb(Ni1/3Nb2/3)O3 (PNN) in the reaction-sintering process were investigated. Only the reflections of raw materials were detected at 400°C. For pellets heated to 500°C, pyrochlore phase Pb2Nb2O7 (P2N2) are found. Cubic Pb3Nb4O13 (P3N4) pyrochlore phase formed and became the main phase in pellets heated to 600°C. After being heated to 800°C, Pb3Nb2O8 (P3N2) pyrochlore phase formed in the pellets. As the pellets were heated to 900°C, the peak of NiNb2O6 columbite phase appeared. In pellets heated to 950°C, the weak peaks of PNN perovskite phase appeared. This means the perovskite phase formed at a temperature between 900°C and 950°C. As the pellets were heated to 1000°C, a large amount of PNN was formed and became dominant. The PbO, NiNb2O6 and Pb3Nb2O8 phases disappeared. The P3N4 content increased with temperature in pellets heated to 1050–1200°C. For pellets heated to 1250°C, the P3N4 content decreased significantly.

(Ybx Y1-x)2O3 (x = 0.0, 0.005, 0.05, 0.08 and 0.15) promising single crystal laser rods of 4.2 mm in diameter and 15–20 mm in length have been grown from the rhenium crucible by the micro-pulling-down method in Ar + H2(3–4%) atmosphere. Linear decrease of lattice constant with the increase of Yb3+-content was observed. High homogeneity of the Yb3+-dopant distribution has been demonstrated. Absorption, emission and Raman spectra have been recorded and decay time was approximated.

Powder mixtures of 3Ti/SiC/C/xAl with different Al contents (x=0∼0.2) were reactively sintered by pulse discharge sintering (PDS) process, to reveal the effect of Al addition on the single-phase bulk Ti3SiC2 synthesis. It was found that the optimal sintering temperature for the Ti3SiC2 synthesis is greatly decreased by the Al addition. Almost single-phase bulk Ti3SiC2 material can be synthesized from 3Ti/SiC/C/0.15Al and 3Ti/SiC/C/0.20Al powder mixtures at temperature as low as 1200°C for 15 min by PDS. And the optimal temperature range for the Ti3SiC2 formation is enlarged obviously by the Al addition.

We report a density functional theory study of the structure and energies of point defects in silver chloride. The localisation of photoelectrons and corresponding holes at these defects has been studied, along with the corresponding relaxation of the lattice. We have applied state-of-the-art periodic and QM/MM embedding methods, to provide new insights into the long-standing problem of the fundamental processes controlling latent image formation.

Containerless processing is an attractive synthesis technique that permits deep undercooling and provides the possibility to solidify the undercooled liquid into a selected phase, and to synthesize materials with novel properties. Spheroidal BaTiO3 samples with a diameter of approximately 2mm were solidified by containerless processing, using an electrostatic levitation apparatus. Single crystal hexagonal BaTiO3 and polycrystalline perovskite BaTiO3 were successfully synthesized at different undercoolings levels. An oxygen-deficient single crystal of hexagonal BaTiO3 obtained with this method, exhibited a giant permittivity higher than 100000, with a loss component tanδ of about 0.1 at room temperature. The permittivity showed weak temperature dependence in the 70 K to 300 K range, and a dramatic drop by 2 orders of magnitude below 70 K. In comparison, the polycrystalline perovskite BaTiO3 showed a permittivity of 4000 at room temperature.

We have studied the resistivity and thermoelectric power of Pr0.66R0.04Sr0.3MnO3 where R = Tb, Y, Ho and Er and have analyzed it within a percolative framework. Both resistivity and thermoelectric power quantities were found to show a strong dependence on the disorder (<σ>2) with the high temperature activation energy in both increasing as <σ>2 is increased, implying that as the disorder increases, carriers get more localized. The percolative nature of the thermopower was analyzed assuming that the lattice has coexisting metallic (Smet) and insulating (Sins) components above and below the Curie temperature (TC) which are independent of each other. Hence total S(T) = pSmet(T) + (1-p)Sins with the volume metallic fraction p=1/(1+exp(-Uo(1-T/TC)/kBT) [1]. A similar analysis was done using the resistivity data. It was seen that the TC from both thermopower and resistivity fits were nearly the same indicating that they have a common origin. This analysis clearly proves that the metal insulator transition in manganites is percolative in nature and that the transport properties show a strong percolation tendency.

This work is focused on the sol-gel synthesis of pure and Ca-doped LaCoO3 nanopowders. The samples were prepared starting from methanolic solutions of cobalt (II) acetate (Co(CH3COO)2·4H2O), lanthanum (III) nitrate (La(NO3)3·6H2O) and calcium (II) acetate (Ca(CH3COO)2·H2O). After solvent evaporation, the obtained powders were dried under vacuum and subsequently treated in air up to 1273 K. The system evolution under thermal annealing was studied by X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM), while the chemical composition was analyzed by X-ray Photoelectron (XPS) and X-ray Excited Auger electron (XE-AES) spectroscopies. The temperature and field dependence of the magnetic properties of the Ca-doped samples were investigated, and compared to those of the corresponding pure LaCoO3 powders.

VO2 (M) nanorods have been synthesized and the morphology and structure of the sample were characterized by XRD, SEM, and HRTEM. The results show that for VO2 (M) nanorods, the transition temperature is 65 °C and the hysteresis loop width is 8 °C. The active energy of low temperature semiconducting phase is 0.2eV, which indicates that its Fermi energy level situates on the middle energy level of the forbidden-band. The doping of Mo6+ decreases its transition temperature.

With the preparation of organic-inorganic layered perovskite-type compounds (C4H9NH3)2MCl4 (M = Mn, Cu) in solutions, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetry (TG) and differential scanning calorimetry (DSC) have been used to characterize the obtained powders. XRD patterns demonstrate that the two compounds have obvious layered structures and SEM pictures reveal that both (C4H9NH3)2MnCl4 and (C4H9NH3)2CuCl4 take on obvious sheet-like microstructure. TG&DSC curves indicate that (C4H9NH3)2CuCl4 decomposes at much lower temperature than (C4H9NH3)2MnCl4.This is ascribed to weakening interactions between its organic and inorganic components, which is presumably due to the Jahn-Teller distortion of [CuCl6] octahedra.

Three key factors influencing the refractive indices of inorganic solid state materials were discussed on the basis of the concept of optical channels and the dielectric functions calculated for two series of closely related oxides. Implications of our observation concerning efficient UV blockers were discussed.

The existence of Ti3N4 was proposed as the first product of the thermal decomposition of precipitates obtained in ammonolysis reactions of titanium(IV) dialkylamides. The evidence is re-evaluated and further evidence is presented to demonstrate that these materials are probably TiN contaminated with carbon. However, this precursor system is demonstrated to be a good route to finely divided, nanocrystalline TiN powders.

The importance of silicon oxynitride (SiOxNy) for optoelectronic device applications is ever increasing owing to its tunable refractive index. In this research, the influence of deposition conditions on film properties, correlated with film composition and bonding, have been investigated. Thick SiOxNy films were deposited in a plasma enehanced chemical vapor deposition reactor using silane (SiH4) and nitrous oxide (N2O) as precursor gases. To investigate the influence of deposition conditions on film properties, three different parameters were studied; gas flow ratio, RF plasma mixed frequency ratio and RF power. Several different SiOxNy films were deposited at varying conditions. The temperature and pressure were maintained at 350°C and 1 Torr during all the experimental runs. The films were characterized for refractive index, growth rate and residual stress. The refractive index and the thickness of the films were measured using a prism-coupling technique. For composition analysis, x-ray photoelectron spectroscopy studies and elastic recoil detection analysis were undertaken. The materials analysis was used to determine the correlation between growth parameters and material chemistry. In addition, the correlation between material chemistry and refractive index was also investigated.