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At least 865 records · Page 48
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DOE OSTI2011

Structural and magnetic properties of Nd{sub 18}Li{sub 8}Co{sub 4-x}Fe{sub x}O{sub 39-y} and Nd{sub 18}Li{sub 8}Co{sub 4-x}Ti{sub x}O{sub 39-y}

Nd{sub 18}Li{sub 8}Co{sub 3}FeO{sub 39-y}, Nd{sub 18}Li{sub 8}CoFe{sub 3}O{sub 39-y} and Nd{sub 18}Li{sub 8}Co{sub 3}TiO{sub 39-y} have been synthesised and characterised by neutron powder diffraction, magnetometry and Moessbauer spectroscopy. Their cubic structure (Pm3-bar n, a{approx}11.9 A) is based on intersecting <1 1 1> chains comprised of alternating octahedral and trigonal-prismatic coordination sites. These chains lie within hexagonal-prismatic cavities formed by a Nd-O framework. Each compound has an incomplete oxide sublattice (y{approx}1), with vacancies located around the octahedral sites that lie at the points of chain intersection. These sites are fully occupied by a disordered arrangement of transition-metal cations but only 75% of the remaining octahedral sites are occupied. The trigonal-prismatic sites are fully occupied by lithium except in the case of Nd{sub 18}Li{sub 8}CoFe{sub 3}O{sub 39-y} where some iron is present. Antiferromagnetic interactions are present on the Nd sublattice in each composition, but a spin glass forms below 5 K when a high concentration of spins is also present on the octahedral sites. - Graphical Abstract: Cation and anion vacancies are found to coexist in mixed-metal oxides that adopt the La{sub 18}Li{sub 8}Rh{sub 5}O{sub 39} structure. Highlights: > Coexistence of anion and cation vacancies in compounds adopting the La{sub 18}Li{sub 8}Rh{sub 5}O{sub 39} structure. > Variation of the degree of magnetic frustration with the chemical composition in the La{sub 18}Li{sub 8}Rh{sub 5}O{sub 39} structure. > Controlling influence of the magnetic properties of the lanthanide cation becomes clear.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Crystal structure of Eu-doped magnetoplumbite-type lanthanum aluminum oxynitride with emission site splitting

Eu-doped lanthanum aluminum oxynitride (LaAl{sub 12}(O,N){sub 19}) with magnetoplumbite structure was prepared by nitridation of the oxide precursor obtained from aluminum glycine gel and subsequent post-annealing. Eu-doped lanthanum aluminum oxynitride exhibited blue light emission at 440 nm with a shoulder at 464 nm under excitation at 254 nm. Isostructural Eu-doped calcium aluminum oxide (CaAl{sub 12}O{sub 19}) exhibited a single emission peak at 415 nm. Structural refinement using neutron powder diffraction indicated that the lanthanum site occupied partially by Eu{sup 2+} splits into 2d and 6h sites in the aluminum oxynitride. The longer emission and the shoulder peak in the former aluminum oxynitride were observed in relation to the increasing covalency as well as crystal field splitting around doped Eu{sup 2+} induced by site splitting involved with the two kinds of anions. - Graphical Abstract: Magnetoplumbite type Eu-doped lanthanum aluminum oxynitride has lanthanum site splitting induced by two kinds of anions, causing two emission peaks. Highlights: > Magnetoplumbite type LaAl{sub 12}(O,N){sub 19} doped with Eu shows emission peak splitting. > ND analysis is performed on La{sub 0.97}Eu{sub 0.03}Al{sub 12}(O,N){sub 19} and Ca{sub 0.97}Eu{sub 0.03}Al{sub 12}O{sub 19}. > La{sub 0.97}Eu{sub 0.03}Al{sub 12}(O,N){sub 19} has lanthanum site splitting. > The lanthanum site splitting is induced by coexisting of two kinds of anions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Ternary system Er-Ni-In at T=870 K

Isothermal section of the Er-Ni-In system at T=870 K was constructed by means of X-ray powder diffraction and EDX-analyses. Nine ternary compounds, namely ErNi{sub 9}In{sub 2} (YNi{sub 9}In{sub 2}-type), Er{sub 1-1.22}Ni{sub 4}In{sub 1-0.78} (MgCu{sub 4}Sn-type), Er{sub 10}Ni{sub 9.07}In{sub 20} (Ho{sub 10}Ni{sub 9}In{sub 20}-type), ErNi{sub 1-0.60}In{sub 1-1.40} (ZrNiAl-type), Er{sub 2}Ni{sub 2}In (Mn{sub 2}AlB{sub 2}-type), Er{sub 2}Ni{sub 1.78}In (Mo{sub 2}FeB{sub 2}-type), Er{sub 5}Ni{sub 2}In{sub 4} (Lu{sub 5}Ni{sub 2}In{sub 4}-type), Er{sub 5}Ni{sub 2}In (Mo{sub 5}SiB{sub 2}-type), and Er{sub 13.53}Ni{sub 3.14}In{sub 3.33} (Lu{sub 14}Co{sub 2}In{sub 3}-type), exist in the Er-Ni-In system at this temperature. The substitution of Ni for In was observed for ErNi{sub 1-0.60}In{sub 1-1.40} and In for Er in the case of related compounds ErNi{sub 2} and ErNi{sub 4}In. Er can enter NiIn (CoSn-type) leading to including-substitution type of compound Er{sub 0-0.12}NiIn{sub 1-0.89}. Basic magnetic properties of the Er{sub 0.04}NiIn{sub 0.97}, ErNi{sub 2}, Er{sub 0.9}Ni{sub 2}In{sub 0.1}, and ErNi{sub 4}In phases were inspected. Electrical-resistivity studies were performed on the ErNiIn, ErNi{sub 0.9}In{sub 1.1}, and ErNi{sub 4}In phases. - Graphical Abstract: Phase relations in the ternary system Er-Ni-In have been established for the isothermal section at T=870 K based on X-ray phase and EDX-analyses. Nine ternary compounds were observed. Highlights: > Isothermal section of Er-Ni-In system at T=870 K was constructed. > Nine ternary compounds were detected. > Basic magnetic properties of Er{sub 0.04}NiIn{sub 0.97} and ErNi{sub 4}In phases were inspected.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Photoluminescence of samarium-doped TiO{sub 2} nanotubes

Samarium (Sm)-modified TiO{sub 2} nanotubes (TNTs) were synthesized by low-temperature soft chemical processing. X-ray powder diffraction analyses of the synthesized Sm-doped and non-doped TNTs show a broad peak near 2{theta}=10{sup o}, which is typical of TNTs. The binding energy of Sm {sup 3}d{sub 5/2} for 10 mol% Sm-doped TNT (1088.3 eV) was chemically shifted from that of Sm{sub 2}O{sub 3} (1087.5 eV), showing that Sm existed in the TiO{sub 2} lattice. Sm-doped TNTs clearly exhibited red fluorescence, corresponding to the doped Sm{sup 3+} ion in the TNT lattice. The Sm-doped TNT excitation spectrum exhibited a broad curve, which was similar to the UV-vis optical absorption spectrum. Thus, it was considered that the photoluminescence emission of Sm{sup 3+}-doped TNT with UV-light irradiation was caused by the energy transfer from the TNT matrix via the band-to-band excitation of TiO{sub 2} to the Sm{sup 3+} ion. - Graphical Abstract: Samarium-doped TiO{sub 2} nanotubes (TNTs) having a nanotubular structure were synthesized by soft chemical route. It was revealed that the energy associated by the band-to-band excitation of TNT matrix transferred to the doped Sm{sup 3+} ions in the lattice, resulting in emission of strong and visible red fluorescence. Highlights: > Sm-doped TiO{sub 2} nanotubes synthesized by low-temperature soft chemical processing. > Sm{sup 3+} substitutes Ti{sup 4+} ions in the nanotube lattice. > Clear fluorescent emission due to the f-f transition at the Sm{sup 3+} in a crystal field environment. > Band-to-band excitation of TiO{sub 2} and followed energy transfer to Sm{sup 3+} causes the luminescence.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Synthesis and characterization of the La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} system and the fluorinated phases La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x}

The oxyfluorides La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} have been prepared by fluorination of the precursor oxides La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} via a low temperature route using poly(vinylidene fluoride) (PVDF). The structures of the oxides and oxyfluorides were investigated in detail by the Rietveld analysis of powder diffraction data. The oxyfluorides crystallize in the space group Pnma for 0<x{<=}0.9 (SrFeO{sub 2}F itself is cubic, space group Pm-3m) and show a sort of two-step structural distortion for decreasing x. Furthermore, a structural comparison of the oxyfluorides with the oxides is given, revealing an increase of the volume per La{sub 1-x}Sr{sub x}FeX{sub 3} unit during fluorination, of which the magnitude highly depends on the value of x. - Graphical abstract: The crystal structures of the perovskites La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} for x=0.8 (a), 0.5 (b) and 0.1 (c). Highlights: > Oxyfluorides La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} were prepared via low temperature fluorination using PVDF. > A structural investigation of the compounds La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} is presented in detail. > Differences in structure are discussed in comparison with the precursor oxides La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

High temperature crystal structures and superionic properties of SrCl{sub 2}, SrBr{sub 2}, BaCl{sub 2} and BaBr{sub 2}

The structural properties of the binary alkaline-earth halides SrCl{sub 2}, SrBr{sub 2}, BaCl{sub 2} and BaBr{sub 2} have been investigated from ambient temperature up to close to their melting points, using the neutron powder diffraction technique. Fluorite-structured SrCl{sub 2} undergoes a gradual transition to a superionic phase at 900-1100 K, characterised by an increasing concentration of anion Frenkel defects. At a temperature of 920(3) K, the tetragonal phase of SrBr{sub 2} undergoes a first-order transition to a cubic fluorite phase. This high temperature phase shows the presence of extensive disorder within the anion sublattice, which differs from that found in superionic SrCl{sub 2}. BaCl{sub 2} and BaBr{sub 2} both adopt the cotunnite crystal structure under ambient conditions. BaCl{sub 2} undergoes a first-order structural transition at 917(5) K to a disordered fluorite-structured phase. The relationship between the (disordered) crystal structures and the ionic conductivity behaviour is discussed and the influence of the size of the mobile anion on the superionic behaviour is explored. - Graphical abstract: Anomalous behaviour of the lattice expansion of SrCl{sub 2} at temperatures of {approx}1000 K is associated with the gradual transition to a superionic phase, whilst SrBr{sub 2} undergoes a first-order structural transition ({beta}{yields}{alpha}) to a fluorite-structured superionic phase at 920(3) K. Highlights: > Anomalous behaviour of the lattice expansion of SrCl{sub 2} occurs at temperatures {approx}1000 K. > Crystal structure of {beta}-SrBr{sub 2} is described in detail. > On heating, SrBr{sub 2} and BaCl{sub 2} transform to a fluorite-structured superionic phase. > Temperature dependence of the BaCl{sub 2} and BaBr{sub 2} structures is presented. > Nature of the superionic phases within the alkaline-earth halides is discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Evidence of a transition to reorientational disorder in the cubic alkali-metal dodecahydro-closo-dodecaborates

A neutron powder diffraction and differential scanning calorimetry (DSC) study indicates that Cs{sub 2}B{sub 12}H{sub 12} undergoes a second-order phase transition near 529 K that can be described as a reorientational disordering of the B{sub 12}H{sub 12}{sup 2-} icosahedral anions between two lowest-energy configurations within the cubic structure. Such a disordering requires the addition of another mirror plane to the low-temperature Fm3-bar structural symmetry to become Fm3-bar m. Differential scanning calorimetry measurements suggest the possible persistence of some short-range anion order at and above the transition. Additional DSC measurements of the lighter alkali-metal cubic isomorphs, Rb{sub 2}B{sub 12}H{sub 12} and K{sub 2}B{sub 12}H{sub 12}, also indicate second-order transitions for these compounds near 742 K and 811 K, respectively. These results are suggestive of similar order-disorder phase changes as for Cs{sub 2}B{sub 12}H{sub 12}, although confirmation of their existence requires analogous diffraction measurements. - Graphical Abstract: Cs{sub 2}B{sub 12}H{sub 12} undergoes an order-disorder phase transition near 529 K. Similar transitions are observed for K{sub 2}B{sub 12}H{sub 12} and Rb{sub 2}B{sub 12}H{sub 12}. Highlights: > Diffraction and DSC reveal that Cs{sub 2}B{sub 12}H{sub 12} undergoes a 2nd-order phase transition near 529 K. > This phase transition is from the low-temperature Fm3-bar symmetry to Fm3-bar m at high temperatures. > DSC of Rb{sub 2}B{sub 12}H{sub 12} and K{sub 2}B{sub 12}H{sub 12} indicate 2nd-order transitions near 742 K and 811 K, respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Oriented SrFe{sub 12}O{sub 19} thin films prepared by chemical solution deposition

Thin films of SrFe{sub 12}O{sub 19} (SrM) were prepared from a solution of iron and strontium alkoxides through the chemical solution deposition method on both amorphous (glassy SiO{sub 2}), and single crystal substrates (Si(100), Si(111), Ag(111), Al{sub 2}O{sub 3}(001), MgO(111), MgAl{sub 2}O{sub 4}(111), SrTiO{sub 3}(111)) substrates. The process of crystallization was investigated by means of powder diffraction, atomic force microscopy and scanning electron microscopy. Magnetization measurements, ferromagnetic and nuclear magnetic resonance were used for evaluation of anisotropy in the films. Whilst amorphous substrates enabled growth of randomly oriented SrM phase, use of single crystal substrates resulted in samples with different degree of oriented growth. The most pronounced oriented growth was observed on SrTiO{sub 3}(111). A detailed inspection revealed that growth of SrM phase starts through the breakup of initially continuous film into isolated grains with expressive shape anisotropy and hexagonal habit. A continuous film with epitaxial relations to the substrate was produced by repeating recoating and annealing. - Graphical Abstract: XRD and AFM patterns of SrFe{sub 12}O{sub 19} thin film epitaxially grown on SrTiO{sub 3}(111) single crystal using seeding layer templating. Highlights: > Single phase SrFe{sub 12}O{sub 19} thin films prepared by chemical solution deposition. > Epitaxial growth on SrTiO{sub 3}(111) with (00l)SrM//(111)SrTiO{sub 3}, <110>SrM//<110>SrTiO{sub 3}). > Seed layer breaks into isolated single crystal islands and serves as a template. > Larger seed grains grow by consuming the grains within the bulk of recoated film.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Pb{sub 2.85}Ba{sub 2.15}Fe{sub 4}SnO{sub 13}: A new member of the A{sub n}B{sub n}O{sub 3n-2} anion-deficient perovskite-based homologous series

Pb{sub 2.85}Ba{sub 2.15}Fe{sub 4}SnO{sub 13}, a new n=5 member of the anion-deficient perovskite based A{sub n}B{sub n}O{sub 3n-2} (A=Pb, Ba, B=Fe, Sn) homologous series, was synthesized by the solid state method. The crystal structure of Pb{sub 2.85}Ba{sub 2.15}Fe{sub 4}SnO{sub 13} was investigated using a combination of neutron powder diffraction, electron diffraction, high angle annular dark field scanning transmission electron microscopy and Moessbauer spectroscopy. It crystallizes in the Ammm space group with unit cell parameters a=5.7990(1) A, b=4.04293(7) A and c=26.9561(5) A. The Pb{sub 2.85}Ba{sub 2.15}Fe{sub 4}SnO{sub 13} structure consists of quasi two-dimensional perovskite blocks separated by 1/2[110](1-bar 01){sub p} crystallographic shear (CS) planes. The corner-sharing FeO{sub 6} octahedra at the CS planes are transformed into edge-sharing FeO{sub 5} distorted tetragonal pyramids. The octahedral positions in the perovskite blocks between the CS planes are jointly taken up by Fe and Sn, with a preference of Sn towards the position at the center of the perovskite block. The chains of FeO{sub 5} pyramids and (Fe,Sn)O{sub 6} octahedra of the perovskite blocks delimit six-sided tunnels at the CS planes occupied by double chains of Pb atoms. The compound is antiferromagnetically ordered below T{sub N}=368{+-}15 K. Highlights: Black-Right-Pointing-Pointer Compound Pb{sub 2.85}Ba{sub 2.15}Fe{sub 4}SnO{sub 13} was synthesized and characterized for the first time. Black-Right-Pointing-Pointer It is a new member of the anion-deficient perovskite based homologous series A{sub n}B{sub n}O{sub 3n-2} with n=5. Black-Right-Pointing-Pointer Its structure consists of quasi two-dimensional perovskite blocks separated by interfaces. Black-Right-Pointing-Pointer Interfaces are made up of edge-sharing FeO{sub 5} distorted tetragonal pyramids. Black-Right-Pointing-Pointer Pb{sub 2.85}Ba{sub 2.15}Fe{sub 4}SnO{sub 13} is antiferromagnetically ordered below T{sub N}=368{+-}15 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Synthesis, structure, and optical properties of CsU{sub 2}(PO{sub 4}){sub 3}

CsU{sub 2}(PO{sub 4}){sub 3} was synthesized in highest yield by the reaction in a fused-silica tube of U, P, and Se in a CsCl flux at 1273 K. It crystallizes with four formula units in space group P2{sub 1}/n of the monoclinic system in a new structure type. The structure of CsU{sub 2}(PO{sub 4}){sub 3} is composed of U and Cs atoms coordinated by PO{sub 4}{sup 3-} units in distorted octahedral arrangements. Each U atom corner shares with six PO{sub 4}{sup 3-} units. Each Cs atom face shares with one, edge shares with two, and corner shares with three PO{sub 4}{sup 3-} units. The structure shares some features with the sodium zirconium phosphate structure type. X-ray powder diffraction results demonstrate that the present CsU{sub 2}(PO{sub 4}){sub 3} compound crystallizes in a structure different from the previously reported {beta} Prime - and {gamma}-CsU{sub 2}(PO{sub 4}){sub 3} compounds. CsU{sub 2}(PO{sub 4}){sub 3} is highly pleochroic, as demonstrated by single-crystal optical absorption measurements. - Graphical abstract: Stacking of the layers in CsU{sub 2}(PO{sub 4}){sub 3}, viewed along [100]. Highlights: Black-Right-Pointing-Pointer Compound CsU{sub 2}(PO{sub 4}){sub 3} crystallizes in a new structure type. Black-Right-Pointing-Pointer Structure shares some features with the sodium zirconium phosphate structure type. Black-Right-Pointing-Pointer CsU{sub 2}(PO{sub 4}){sub 3} is highly pleochroic, as demonstrated by single-crystal optical absorption measurements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

{sup 45}Sc Solid State NMR studies of the silicides ScTSi (T=Co, Ni, Cu, Ru, Rh, Pd, Ir, Pt)

The silicides ScTSi (T=Fe, Co, Ni, Cu, Ru, Rh, Pd, Ir, Pt) were synthesized by arc-melting and characterized by X-ray powder diffraction. The structures of ScCoSi, ScRuSi, ScPdSi, and ScIrSi were refined from single crystal diffractometer data. These silicides crystallize with the TiNiSi type, space group Pnma. No systematic influences of the {sup 45}Sc isotropic magnetic shift and nuclear electric quadrupolar coupling parameters on various structural distortion parameters calculated from the crystal structure data can be detected. {sup 45}Sc MAS-NMR data suggest systematic trends in the local electronic structure probed by the scandium atoms: both the electric field gradients and the isotropic magnetic shifts relative to a 0.2 M aqueous Sc(NO{sub 3}){sub 3} solution decrease with increasing valence electron concentration and within each T group the isotropic magnetic shift decreases monotonically with increasing atomic number. The {sup 45}Sc nuclear electric quadrupolar coupling constants are generally well reproduced by quantum mechanical electric field gradient calculations using the WIEN2k code. Highlights: Black-Right-Pointing-Pointer Arc-melting synthesis of silicides ScTSi. Black-Right-Pointing-Pointer Single crystal X-ray data of ScCoSi, ScRuSi, ScPdSi, and ScIrSi. Black-Right-Pointing-Pointer {sup 45}Sc solid state NMR of silicides ScTSi.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Mixed crystal formation and structural studies in the mullite-type system Bi{sub 2}Fe{sub 4}O{sub 9}-Bi{sub 2}Mn{sub 4}O{sub 10}

The limits of metal cation substitution and distribution in the sequence Bi{sub 2}Fe{sub 4}O{sub 9}-Bi{sub 2}Mn{sub 4}O{sub 10} have been investigated by solid state synthesis, X-ray powder diffraction, and Moessbauer spectroscopy. Rietveld refinements conducted for the entire range along the join indicate the structures are orthorhombic with space group Pbam, with partial transition-metal site disorder confirmed and detailed by Moessbauer spectroscopy. Single-phase regions are found near each end-member and a two-phase region is observed at intermediate compositions, extending from about x=1 to 3, according to the general formula of the mixed crystals Bi{sub 2}Fe{sub 4-x}Mn{sub x}O{sub 10-{delta}}. An incorporation of Mn at octahedral sites replacing Fe is taken into account for the Bi{sub 2}Fe{sub 4}O{sub 9}-related side of the system. Charge compensation is believed to be effected by addition of O, which gives rise to the formation of FeO{sub 5} pyramids. At the Bi{sub 2}Mn{sub 4}O{sub 10}-related side of the system, substitution of pyramidal Mn{sup 3+} by Fe{sup 3+} is envisaged. - Graphical abstract: Single-phase regions are found near each end-member and a two-phase region is observed at intermediate compositions, extending from about x=1 to 3, according to the general formula of the mixed crystals Bi{sub 2}Fe{sub 4-x}Mn{sub x}O{sub 10-{delta}}. Highlights: Black-Right-Pointing-Pointer Mixed crystals of the mullite-type Bi{sub 2}Fe{sub 4-x}Mn{sub x}O{sub 10-{delta}} were synthesized. Black-Right-Pointing-Pointer Two single-phase regions and an intermediate two-phase region were found. Black-Right-Pointing-Pointer Site substitution was examined via X-ray diffraction and Moessbauer spectroscopy. Black-Right-Pointing-Pointer Charge compensation models were examined for intermediate compositions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Hematite homogeneous core/shell hierarchical spheres: Surfactant-free solvothermal preparation and their improved catalytic property of selective oxidation

Solvothermal synthesis is an efficient synthetic method for preparing nano and micromaterials. Preparation of hematite through alcoholysis of ferric ion under solvothermal condition has been carried out at low concentrations. In this paper, Fe{sub 2}O{sub 3} homogeneous core/shell hierarchical nanostructures were synthesized via solvothermal treatment of FeCl{sub 3}{center_dot}6H{sub 2}O and ethanol. The achievements of such structures can be attributed to two important factors: high temperature and high concentration. Besides, the crystal water and reaction time were also important factors to the synthesis of hematite. The prepared samples were characterized using X-ray powder diffraction, Raman spectra, scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer, transmission electron microscopy and Brunauer-Emmett-Teller surface area and pore size distribution. X-ray photoelectron spectroscopy showed a satellite peak at 719.8 eV, which is the characteristic peak of Fe(III). The formation mechanism of the spheres and the effects of the reactant concentrations and reaction temperatures have been discussed. Moreover, the enhanced catalytic activity of the spheres has also been investigated through oxidation of benzyl alcohol to benzaldehyde with high conversion (42%) and selectivity (95%). - Graphical abstract: Fe{sub 2}O{sub 3} homogeneous core/shell hierarchical microspheres were synthesized by solvothermal method. Owing to the special structure, the synthesized Fe{sub 2}O{sub 3} microspheres exhibit a superior catalytic activity in benzyl oxidation. Highlights: Black-Right-Pointing-Pointer Hierarchical Fe{sub 2}O{sub 3} core/shell microspheres were synthesized. Black-Right-Pointing-Pointer Microspheres were assembled by {beta}-FeOOH. Black-Right-Pointing-Pointer The sample exhibits a superior catalytic activity and selectivity. Black-Right-Pointing-Pointer The high activity and selectivity are due to the hierarchical core/shell structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Structures of ordered tungsten- or molybdenum-containing quaternary perovskite oxides

The room temperature crystal structures of six A{sub 2}MMoO{sub 6} and A{sub 2}MWO{sub 6} ordered double perovskites were determined from X-ray and neutron powder diffraction data. Ba{sub 2}MgWO{sub 6} and Ba{sub 2}CaMoO{sub 6} both adopt cubic symmetry (space group Fm3-bar m, tilt system a{sup 0}a{sup 0}a{sup 0}). Ba{sub 2}CaWO{sub 6} has nearly the same tolerance factor (t=0.972) as Ba{sub 2}CaMoO{sub 6} (t=0.974), yet it surprisingly crystallizes with I4/m symmetry indicative of out-of-phase rotations of the MO{sub 6} octahedra about the c-axis (a{sup 0}a{sup 0}c{sup -}). Sr{sub 2}ZnMoO{sub 6} (t=0.979) also adopts I4/m symmetry; whereas, Sr{sub 2}ZnWO{sub 6} (t=0.976) crystallizes with monoclinic symmetry (P2{sub 1}/n) with out-of-phase octahedral tilting distortions about the a- and b-axes, and in-phase tilting about the c-axis (a{sup -}a{sup -}c{sup +}). Ca{sub 2}CaWO{sub 6} (t=0.867) also has P2{sub 1}/n symmetry with large tilting distortions about all three crystallographic axes and distorted CaO{sub 6} octahedra. Analysis of 93 double perovskites and their crystal structures showed that while the type and magnitude of the octahedral tilting distortions are controlled primarily by the tolerance factor, the identity of the A-cation acts as the secondary structure directing factor. When A=Ba{sup 2+} the boundary between cubic and tetragonal symmetries falls near t=0.97, whereas when A=Sr{sup 2+} this boundary falls somewhere between t=1.018 and t=0.992. - Graphical abstract: A survey of the tolerance factor of 41 Mo/W- and 52 Nb/Ta-containing quaternary perovskites plotted as a function of the difference between the two six-coordinate M-cation ionic radii. Compounds with cubic symmetry are represented by diamonds, those with tetragonal symmetry are represented by squares, those with I2/m monoclinic symmetry are represented by Multiplication-Sign , and those with P2{sub 1}/n monoclinic symmetry are represented by triangles. White symbols represent compositions where A=Ba{sup 2+}, gray symbols represent compositions where A=Sr{sup 2+}, and black symbols represent where A=Ca{sup 2+}. The filled circle represents rhombohedral Ba{sub 2}BiTaO{sub 6} (t=0.961; space group-R3-bar ; tilt system-a{sup -}a{sup -}a{sup -}). References for the compounds included in this figure are listed in the Supporting Information File. Black-Small-Square Highlights: Black-Right-Pointing-Pointer Reports the structures of six double perovskites containing either Mo{sup 6+} or W{sup 6+}. Black-Right-Pointing-Pointer Compounds with similar tolerance factors (t) exhibited different symmetries. Black-Right-Pointing-Pointer This effect was observed in Sr{sub 2}ZnMO{sub 6} and Ba{sub 2}CaMO{sub 6} (M=Mo or W). Black-Right-Pointing-Pointer Contains a structural survey of 93 double perovskites. Black-Right-Pointing-Pointer Octahedral tilting distortions are controlled by t and the nature of the A-cation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Two types of rare earth-organic frameworks constructed by racemic tartaric acid

Hydrothermal reactions of rare earth oxides with racemic tartaric acid (H{sub 2}tar) yielded 7 rare earth(III) MOFs with general formulas [R{sub 2}(tar){sub 3}(H{sub 2}O){sub 2}]{sub n} (R=Y (1), Sm (4), Eu (5), Tb (6), Dy (7)) and [R{sub 2}(tar){sub 2}(C{sub 2}O{sub 4})(H{sub 2}O){sub 2}]{sub n}{center_dot}4nH{sub 2}O (R=La (2), Nd (3)). X-ray powder diffraction analysis and single-crystal X-ray diffraction analysis reveal that they present two different structural types. MOFs 1, 4, 5, 6 and 7 are isostructural and crystallize in the orthorhombic non-centrosymmetric space group Iba2, and feature unusual fsc-3,4-Iba2 topology. MOFs 2 and 3 are isostructural and crystallize in monoclinic P2{sub 1}/c space group and display rare fsx-4,5-P2{sub 1}/c topology containing hydrophilic channels bounded by triple helical chains along a axis. MOFs 3, 4, 5, 6 and 7 exhibit intense lanthanide characteristic photoluminescence at room temperature. - Graphical Abstract: [R{sub 2}(tar){sub 2}(C{sub 2}O{sub 4})(H{sub 2}O){sub 2}]{sub n}{center_dot}4nH{sub 2}O (R=La (2), Nd (3)) display rare fsx-4,5-P2{sub 1}/c topology containing hydrophilic channels bounded by triple helical chains along a axis. Highlights: Black-Right-Pointing-Pointer Two types of rare earth MOFs were synthesized by hydrothermal conditions. Black-Right-Pointing-Pointer MOFs feature unusual fsc-3,4-Iba2 and rare fsx-4,5-P2{sub 1}/c topology structures. Black-Right-Pointing-Pointer MOFs exhibit intense lanthanide characteristic photoluminescence.

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DOE OSTI2012

Biomolecule-assisted hydrothermal synthesis of silver bismuth sulfide with nanostructures

Silver bismuth sulfide (AgBiS{sub 2}) nanostructures were successfully prepared via a simple biomolecule-assisted hydrothermal synthesis at 200 Degree-Sign C for 12-72 h. Silver nitrate, bismuth nitrate and L-cysteine were used as starting materials. Here, the biomolecule, L-cysteine, was served as the sulfide source and a complexing agent. The products, characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), were cubic AgBiS{sub 2} nanoparticles with a diameter range of about 20-75 nm. It was found that their crystallinity and particle size increased with increasing reaction time. The energy dispersive X-ray spectroscopy (EDX) and inductively coupled plasma optical emission spectrophotometry (ICP-OES) analyses were used to confirm the stoichiometry of AgBiS{sub 2}. The optical band gap of the AgBiS{sub 2} nanoparticles, calculated from UV-vis spectra, was 3.0 eV which indicated a strong blue shift because of the quantum confinement effect. A possible formation mechanism of the AgBiS{sub 2} nanoparticles was also discussed. - Graphical abstract: The optical band gap of the as-prepared AgBiS{sub 2} nanoparticles displays a strong blue shift comparing to the 2.46 eV of bulk AgBiS{sub 2} caused by the quantum confinement effects. Highlights: Black-Right-Pointing-Pointer A simple biomolecule-assisted hydrothermal method is developed to prepare AgBiS{sub 2}. Black-Right-Pointing-Pointer L-Cysteine is served as the sulfide source and a complexing agent. Black-Right-Pointing-Pointer Increase in band gap of the AgBiS{sub 2} nanoparticles attributes to the quantum confinement effects.

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DOE OSTI2012

Structural chemistry and spin-glass behaviour of Nd{sub 18}Li{sub 8}Fe{sub 4}TiO{sub 39}

Nd{sub 18}Li{sub 8}Fe{sub 4}TiO{sub 39} has been synthesised and characterised by neutron powder diffraction, X-ray absorption spectroscopy, Moessbauer spectroscopy and magnetometry. The cubic structure (Pm3-bar n, a=11.97227(8) A) is based on intersecting Left-Pointing-Angle-Bracket 1 1 1 Right-Pointing-Angle-Bracket chains comprised of alternating octahedral and trigonal-prismatic coordination sites. These chains lie within hexagonal-prismatic cavities formed by a Nd-O framework. The larger of the two crystallographically distinct octahedral sites, 8e, is occupied by iron, titanium and lithium in a ratio of 76:20:4; the smaller, 2a, is occupied by iron and titanium in a ratio of 79:21. The trigonal-prismatic site, 16i, is occupied by lithium and iron in a ratio of 98:2. The cations on the 2a sites are assigned as Ti{sup 4+}and low-spin Fe{sup 4+}, and those on the 16i sites as Li{sup +} and Fe{sup 3+}. The 8e sites are thought to be occupied by Li{sup +}, Fe{sup 3+} and Ti{sup 3+}. Nd{sub 18}Li{sub 8}Fe{sub 4}TiO{sub 39} undergoes a transition to a spin-glass state at 4.25(5) K. - Graphical abstract: Nd{sub 18}Li{sub 8}Fe{sub 4}TiO{sub 39} undergoes a transition to a spin-glass state at 4.25(5) K. Highlights: Black-Right-Pointing-Pointer Spin-glass behaviour in Nd{sub 18}Li{sub 8}Fe{sub 4}TiO{sub 39} below 4.25 K. Black-Right-Pointing-Pointer Application of X-ray absorption spectroscopy to a complex mixed-metal oxide. Black-Right-Pointing-Pointer Mixed-valence cations in Nd{sub 18}Li{sub 8}Fe{sub 4}TiO{sub 39}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Why MnIn{sub 2}O{sub 4} spinel is not a transparent conducting oxide?

The title compound has been synthesized by a citrate technique. The crystal structure has been investigated at room temperature from high-resolution neutron powder diffraction (NPD) data. It crystallizes in a cubic spinel structure, space group Fd3-bar m, Z=8, with a=9.0008(1) A at 295 K. It exhibits a crystallographic formula (Mn{sub 0.924(2)}In{sub 0.076(2)}){sub 8a}(In{sub 1.804(2)}Mn{sub 0.196(2)}){sub 16d}O{sub 4}, where 8a and 16d stand for the tetrahedral and octahedral sites of the spinel structure, respectively, with a slight degree of inversion, {lambda}=0.08. MnIn{sub 2}O{sub 4} shows antiferromagnetic interactions below T{sub N} Almost-Equal-To 40 K, due to the statistical distribution of Mn ions over the two available sites. Unlike the related MgIn{sub 2}O{sub 4} and CdIn{sub 2}O{sub 4} spinels, well known as transparent conducting oxides, MnIn{sub 2}O{sub 4} is not transparent and shows a poor conductivity ({sigma}=0.38 S cm{sup -1} at 1123 K): the presence of Mn ions, able to adopt mixed valence states, localizes the charges that, otherwise, would be delocalized in the spinel conduction band. - Graphical Abstract: From NPD data the crystallographic formula (Mn{sub 0.924(2)}In{sub 0.076(2)}){sub 8a}(In{sub 1.804(2)}Mn{sub 0.196(2)}){sub 16d}O{sub 4}, shows a slight degree of inversion, {lambda}=0.08 and a certain In deficiency. The presence of Mn ions, able to adopt mixed oxidation states, localize the charges that, otherwise, would be delocalized in the spinel conduction band; the presence of localized Mn{sup 2+} and Mn{sup 3+} ions provides the characteristic brown color. Highlights: Black-Right-Pointing-Pointer Accurate structural determination from NPD data: inversion degree (8%), and In deficiency. Black-Right-Pointing-Pointer Bond-valence indicates Mn{sup 2+}-Mn{sup 3+} ions; edge-sharing octahedra contain 90% In{sup 3+}+10% Mn{sup 3+} cations. Black-Right-Pointing-Pointer Conductivity several orders of magnitude lower than those of MgIn{sub 2}O{sub 4} or CdIn{sub 2}O{sub 4}. Black-Right-Pointing-Pointer Variability of Mn oxidation states cancels any electron-doping effect, emptying conduction band of mobile charge carriers. Black-Right-Pointing-Pointer Curie-Weiss behavior confirming the determined charge distribution.

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