Both Ba24Si100 and Ba24Ge100 with crystallographically identical structure are the superconductors whose critical temperatures are 1.45 and 0.27 K, respectively. Intriguingly, physical properties of the both compounds are extremely different. The observed differences are considered to be associated with Ba rattling motions. We have exemplified such unique motions in terms of x-ray diffraction data using MEM/Rietveld analyses. We present these exotic systems especially focusing on the relation between superconductivity and the rattling phonons.

A novel perovskite-type oxide PbFeO3 was successfully synthesized under a pressure as high as 7GPa, and the crystal structure, oxidation state, thermal stability, magnetic and dielectric properties were investigated. PbFeO3 possesses an orthorhombic perovskite unit cell and there is no phase transition between room temperature and 570 K. This compound decomposes into Pb2Fe2O5 in the vicinity of 740 K in air. According to XPS, it was found that this compound includes the Pb2+, Pb4+, and Fe3+ ions.

A new family of transition-metal-containing phosphates ANa3M7(PO4)6, where A = K, Rb, Cs and M = Mn, Fe, Co, was synthesized via high-temperature (650-800 °C), solid state reactions. Sizable single crystals up to 1 cm (ca. 160 mg) were grown for structure and property characterization. The extended structure comprises of alternating corner- and edge-sharing triangular chains of FeOn (n = 5,6) polyhedra involving four crystallographically distinct Fe(II) cations. The triangular chains propagate along the a and b directions to form slabs, which are interlinked by P5+ and a fifth Fe2+ cation to form the three-dimensional lattice. The magnetic susceptibility studies suggest that some of these fascinating compounds exhibit a ferromagnetic transition at temperatures between 10K and 15K. The field-dependent studies on the oriented single crystal of RbNa3M7(PO4)6 show the occurrence of magnetization steps at 2 -5K. In this report, we will first discuss some prior research developments relevant to the study of geometrically frustrated magnetic (GFM) interactions, followed by the results of our exploratory synthesis in the pseuo-quaternary iron(II) phosphate system and finally some initial investigations of temperature- and field-dependent magnetic properties.

In this study, we have investigated the synthesis of several Layered Double Hydroxides (LDHs), such as Ni-Ga, Mg-Ga and Ni-Al LDHs with hydrothermal method. Total metal content and ratio of the hydrolysis agent in the reaction solution have found to be determining factors for the crystallinity and morphology of LDH products. In addition, we were able to obtain highly crystalline LDHs in a relatively short reaction times, when the reaction was carried out under stirring at moderately higher temperatures. Delamination of LDHs was carried out in formamide and delamination was confirmed by the images obtained from Atomic Force Microscope (AFM). The observed thickness of sheets was in agreement with the theoretical thickness of LDH layers. Delaminated single nanosize sheets were deposited on a substrate by Layer-by-Layer Assembly (LBL) method, which utilizes the electrostatic attraction principles between oppositely charged units. UV-vis spectroscopy of the films showed that deposition of intercalated LDH thin films with LBL was successfu. Electrochemical properties of the films were also investigated in this study. Cyclic voltammograms of the films revealed that LDH layers and intercalated species are electrochemically active. The redox peaks of Ni/Ni2+ couple were observed for Ni2+ containing LDHs in the region of -0.45 V vs Ag/AgCl. In conclusion, we have demonstrated in this study that various LDH nanosize sheets can be intercalated with anionic species in a Layer-by-Layer deposition manner. In addition, LDH thin films prepared by LBL method showed electrochemical response.

Nanoparticles of lanthanide vanadate (YVO4:Ln) and phosphate (LaPO4:Ln) are obtained by simple aqueous syntheses. The nanoparticles obtained are stabilized in colloidal suspensions and deposited in sol-gel films by spin-coating using a silicate as inorganic binder. The influence of the thermal treatment on the brightness and the ability to achieve multilayer coatings are discussed.

Potassium hexaniobate (K4Nb6O17) is one of the few relatively well-studied oxides which, upon exfoliation, rolls up into scrolls almost quantitatively with monodisperse length (∼300 nm) and diameter (30 nm). The tubes have high surface area (250-300 m2/g) and a wall thickness of 2-3 nm. These H4Nb6O17 scrolls were converted to Nb2O5 via a thermal dehydration process, yielding high surface area (150-200 m2/g) Nb2O5 nanotubes. Despite extensive atomic rearrangement during dehydration at 400-450 °C, little sintering is occurs, and so the tubular morphology is retained. Attempts to conduct further reactions to obtain LiNbO3 and KNbO3 nanotubes from reaction with molten alkali salts failed to yield the intended nanotubular oxides.

We have investigated the effect of high-temperature post-annealing and control of excess oxygen for La1-xSrxMnOy (0.05 ≤ x ≤ 0.2) single crystals. Thin plate-like single crystals prepared by careful cutting and polishing enabled the control of excess oxygen for the single crystals by post-annealing for relatively short times at various temperatures. Post-annealed crystals with y ∼ 3.00 exhibited higher TC than that of as-grown crystals due to homogenization of cation and oxygen compositions and reduction of local lattice strains. With an increase of y, TC systematically increased for all Sr compositions. Competition between an increase of mean valence of manganese and generation of cation vacancy determines the TC of La1-xSrxMnOy crystals.

The mixed-valent compound RBaCo4O7 (R=Rare earth, Y), hereafter abbreviated as R-114, is built up of Kagomé sheets of CoO4 tetrahedra, linked in the third dimension by a triangular layer of CoO4 tetrahedra in an analogous fashion to that found in the known geometrically frustrated magnets such as pyrochlores and SrCr9xGa12-9xO19 (SCGO). We have undertaken a study of the structural and magnetic properties of the Y-114 and Yb-114 compound using combined high resolution powder neutron and synchrotron X-ray diffraction. Both compounds undergo a first order trigonal → orthorhombic phase transition that breaks the trigonal symmetry of the structure. We show from Bond Valence Sum arguments that this transition occurs as a response to a markedly underbonded Ba2+ site in the high-temperature phase. The symmetry-lowering transition relieves the geometric frustration of the structure, and a long-range ordered 3-D antiferromagnetic state develops at low temperature. The magnetic structure of the Y compound has been solved and shows a compromise between the well-known 120° structure of the Kagomé net and a collinear antiferromagnet in the third dimension

Structural and photoluminescence (PL) properties of Zn2(1-x)MnxSiO4 (1 ≤ x ≤ 5) and diffuse reflectance spectroscopy (DRS) and morphological studies of ZnGa2O4:Mn thin film green emitting phosphors grown using pulsed laser deposition (PLD) technique have been investigated. Zn2(1-x)MnxSiO4 thin films grown on Si substrate at 700°C in 300 mTorr of oxygen partial pressure, upon ex-situ annealing at higher temperatures exhibit superior PL intensity. ZnGa2O4:Mn phosphor thin films grown on quartz substrate at 650oC and in-situ annealed in 300mTorr of oxygen partial pressure show better emission intensity. For both Zn2SiO4:Mn and ZnGa2O4:Mn phosphors, luminescence can be assigned to 4T1 – 6A1 transition of Mn2+ within the 3d orbital giving rise to emission at 525 and 503 nm, respectively.

A distinct class of precursor chemistries has been developed for solution-phase deposition of oxide thin films. Rapid liquid-to-solid conversions are facilitated by using high nuclearity species and labile inorganic ligands to promote fast condensation reactions. Consequently, applied deposition strategies differ from conventional sol-gel and surface mediated growth reactions. Select oxide materials have been incorporated in transistor devices and circuits as evidence of thin-film quality and proof of function.

In the Bi2O3-MO-P2O5 diagrams, most of the inorganic frameworks display Bi-M-O polycationic ribbons isolated by XO4 groups and interstitial cationic channels. They are formed of edge sharing O(Bi,M)4 tetrahedra. The width of the ribbons coexisting in the structures and their arrangement is changed from one compound to the next one. Due to mixed Bi3+/M2+ particular positions, a great chemical flexibility and a great degree of disorder may exist. It has been possible to extend ribbons to infinite [Bi2O2]2+ like sheets, sandwiched between XO4 based layers. In addition to this fascinating continuous polymerization from 1D chains to 2D sheets, O(Bi,M)4 and XO4 groups form ideal structural units for the designing of new materials through empirical structural rules that has been established.

Carbon and silicon have been consistently proposed as elements useful in the generation of porous materials. Carbon has been insistently postulated as a promising material to store hydrogen, and crystalline silicogermanate zeolites have recently been synthesized and are being considered in catalytic processes. In the present work we report an approach to generating porous materials, in particular porous carbon and silicon, which leads to the existence of nanopores within the bulk. The method consists in constructing a crystalline diamond-like supercell with 216 atoms with a density (volume) close to the real value, then halving the density by doubling the volume (50% porosity), and subjecting the resulting supercell to an ab initio molecular dynamics process at 300 K for Si, and 1000 K for carbon, followed by geometry relaxation. The resulting samples are essentially amorphous and display pores along some of the “crystallographic” directions. We report their radial distribution functions and the pore structure where prominent.

A large number of composited materials of atomized iron and multiwalled carbon nanotubes have been prepared and sintered at 850°C for one hour. The sintered samples were examined for thermal and for electrochemical corrosion of atomized iron. The results suggest that the composited materials are free from oxidative degradation. The absence of oxidation of atomized iron in nanocomposited environment is attributed to the configurational geometry and spintronics type interaction proposed in recent theoretical calculations.

A layered host material with the ability to encapsulate anionic substances was synthesized by intercalating polycations into a synthetic fluoromica. A cationic polyelectrolyte coiled in the interlayer galleries to overcompensate the negative charge on the silicate sheets, and bulky anionic dye molecules could site-selectively be intercalated into interlayer in which the polyelectorlyte coiled.

Vanadium oxide nanorods intercalated with lithium cations have been successfully formed by the hydrothermal treatment of electrospun precursors. The novelty of this synthesis method is the control of the morphology of the vanadium nanorod precursor by the electrospinning process, and then to convert to the desired compound with loss of the organic polymer while maintaining the morphology through a hydrothermal treatment. Transmission llectron microcopy shows that the single nanorods formed have a square shape cross-section with a width of less than 100nm. Electron diffraction shows that each nanorod is a single crystal, and X-ray diffraction shows that the nanorods have a layered structure with a 10.5 Å layer spacing. Their characterization, magnetic and electrochemical behavior and variable chemical composition are described together with the opportunities electrospinning presents for forming novel materials.

We demonstrate monochromatic and white light optical amplification of the photo-oxidation of adsorbed methylene blue using an inverse colloidal photonic crystal fashioned from anatase nanocrystals, denoted i-nc-TiO2-o. Enhanced photo-activity that drives the oxidation of the dye is attributed to slow photons in i-nc-TiO2-o. When the slow photon wavelength is optimized with respect to the electronic excitation energy of i-nc-TiO2-o, the photo-oxidation rate of the dye is doubled compared to conventional nc-TiO2. By increasing the probability of absorbing photons in i-nc-TiO2-o relative to nc-TiO2, a larger population of electron-hole pairs is generated enabling more efficient photo-oxidation. Slow photons in photonic crystals portend a myriad of opportunities for amplified photo-processes in chemistry and biology.

Two new Dion-Jacobson type layered perovskite solid solutions, RbCa2-xSrxM3O10 (M = Nb, Ta; 0 ≤ x ≤ 2), were prepared and studied by X-ray powder diffraction, neutron powder diffraction, and Raman spectroscopy. X-ray powder diffraction confirmed single-phase solid solution formation with continuous expansion of the idealized primitive tetragonal unit cell with increasing strontium content. Neutron powder diffraction studies of selected samples revealed lower symmetries and larger unit cells, as necessitated by octahedral tilting within the perovskite slabs, compared to the idealized primitive cell. As the average size of the A-cation in the perovskite slab is varied from Sr2+ to Ca2+, more extensive octahedral tilting is introduced. Vibrational modes of the perovskite slab observed using Raman spectroscopy show subtle changes as a function of calcium/strontium content and more intriguing differences between the isostructural niobates and tantalates.