National Institute Of Materials Physics - Romania
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articles found
2211. Influence of orbital contributions to the valence band alignment of Bi2O3, Fe2O3, BiFeO3, and Bi0.5Na0.5TiO3
Authors:
Li, SY; Morasch, J; Klein, A; Chirila, C; Pintilie, L; Jia, LC; Ellmer, K; Naderer, M; Reichmann, K; Groting, M; Albe, K
Published: JUL 17 2013, PHYSICAL REVIEW B, 88, DOI: 10.1103/PhysRevB.88.045428
The formation of an interface between Bi2O3, Fe2O3, BiFeO3, Bi0.5Na0.5TiO3, and the high work function metallic RuO2 is studied using photoelectron spectroscopy with in situ RuO2 deposition. Schottky barrier heights are derived and the valence band maximum energies of the studied materials are aligned with respect to each other as well as to other functional oxides like SrTiO3 and PbTiO3. The energy band alignment follows systematic trends compared to a large number of oxides, and can be understood in terms of the contribution of Fe 3d and Bi 6s/6p (lone pair) orbitals to electronic states near the valence band maximum. The results indicate that the valence band maxima are largely determined by the local environment of the cations, which allows to estimate valence band maximum energies of oxides with multiple cations from those of their parent binary compounds. The high valence band maximum of BiFeO3 is consistent with reported p-type conduction of acceptor doped material, while the high conduction band minimum makes n-type conduction unlikely.
2212. Spectroscopic Investigation of Iron Substitution in EuCoO3: Related Impact on the Catalytic Properties in the High-Temperature N2O Decomposition
Authors:
Wu, Y; Dujardin, C; Granger, P; Tiseanu, C; Sandu, S; Kuncser, V; Parvulescu, VI
Published: JUL 11 2013, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 13999, DOI: 10.1021/jp402211c
2213. Magnetic properties of iron-carbon nanocomposites obtained by laser pyrolysis in specific configurations
Authors:
Schinteie, G; Kuncser, V; Palade, P; Dumitrache, F; Alexandrescu, R; Morjan, I; Filoti, G
Published: JUL 5 2013, JOURNAL OF ALLOYS AND COMPOUNDS, 564, 34, DOI: 10.1016/j.jallcom.2013.02.126
New nanometric systems were produced by using specific parameters of the laser pyrolysis process. Relevant results related to the magnetic behavior of the samples were obtained via SQUID magnetometry and Mossbauer spectroscopy, the data being corroborated with those previously obtained from X-ray diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy. The formed nanocomposites contain iron carbides, iron oxides and metallic iron nanoparticles which relative content and average size depend strongly on experimental specific parameters of the pyrolysis process. The magnetic properties and the local interaction mechanisms were explained by adequate magnetic relaxation and static models. (C) 2013 Elsevier B.V. All rights reserved.
2214. Photoluminescence decay time studies on ZnS in cubic and hexagonal phase and its mechanico-chemical interaction with polyaniline
Authors:
Scocioreanu, M; Mihut, L; Baibarac, M; Baltog, I
Published: JUL 2013, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 250, 1431, DOI: 10.1002/pssb.201248234
We report new photoluminescence (PL) data generated by pulsed optical excitation on the composites achieved by a mechanico-chemical reaction between ZnS in the cubic (c) and wurtzite (w) phases and polyaniline-emeraldine base (PANI-EB). Under continuous and pulsed optical excitation, powders of the (w)ZnS and (w)ZnS/PANI-EB composites display PL with different spectral compositions. Contrary to expectations, the (c)ZnS and the (c)ZnS/PANI-EB composite displayed weak PL and decay time in the range of nanoseconds. This results from the great involvement of the surface states in nanometric powders which creates efficient channels for the non-radiative recombination of the carriers. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
2215. Mechanisms of the Charge Transfer in IrQ(ppy)(2)-5Cl Dual-Emitter Compound
Authors:
Polosan, S; Radu, IC
Published: JUL 2013, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 13, 5208, DOI: 10.1166/jnn.2013.7513
The synthesis of IrQ(ppy)(2)-5Cl has the advantage of a dual phosphorescence (green and red) which comes from the two ligands, phenylpyridine and quinoline. Their spectroscopic properties evidences the absorption range between 350 nm to 700 nm which is composed from the singlet and triplet states, as a result of hybridizations between Ir and the two ligands, the first one being at 625 nm. The first low energy state comes from the quinoline ligand and is responsible for the red phosphorescence at 660 nm, as results from the Density Functional Theory (DFT) analysis. The hybridization between Ir 5d orbitals and pi ligand orbitals shows strong metallic character with phenylpyridine orbitals (66% and 43%) and weak metallic character with quinoline ligand (16.8%). This fact suggests weak phosphorescence intensity in the emission spectra. Population analysis of each metallic orbital shows a small charge delocalization on the quinoline ligand for the first molecular orbital and a strong delocalization on the phenylpyridine ligands. Solvation effects induce a tuning process for the phosphorescence by changing of the matrix of the organometallic compounds which can be adjusted by the strength of intermolecular dipole-dipole interactions, using a doped guest-host molecular organic thin film system.
2216. Nanotubes of piezoelectric BNT-BT0.08 obtained from sol-gel precursor
Authors:
Cernea, M; Trupina, L; Vasile, BS; Trusca, R; Chirila, C
Published: JUL 2013, JOURNAL OF NANOPARTICLE RESEARCH, 15, DOI: 10.1007/s11051-013-1787-y
Barium titanate-substituted bismuth titanate ((Bi0.5Na0.5)(0.92)Ba0.08TiO3, BNT-BT0.08) nanotubes were fabricated using sol-gel chemistry, spin casting, and a porous polycarbonate membrane template. The structure and morphology of the tubes have been investigated by scanning electron microscopy and transmission electron microscopy. The diameter and length of these tubes were about 650 nm and 20 mu m, respectively, and their wall thickness was about 50 nm. The tubes were polycrystalline with average grain size of similar to 40 nm. The BNT-BT0.08 nanotubes exhibited ferroelectric behavior as evidenced by saturated piezoresponse hysteresis loops and phase switching. BNT-BT0.08 piezoelectric nanotubes promise novel device architectures and enhanced electric properties.
2217. TECHNOLOGY OF CHALCOGENIDE GLASSY SEMICONDUCTOR LAYERS FABRICATION
Authors:
Prilepov, V; Popescu, M; Chirita, A; Korshak, O; Ketrush, P; Nasedchina, N
The results of the studies of thin layer structures based on chalcogenide glassy semiconductors (CGS) of As-Se-S system fabrication are presented in the given paper. The possibility of of As-Se-S system thin films obtaining with the given electro-physical parameters, was shown.
2218. Structural and electrical properties of NBT-BT0.08 ceramic prepared by the pyrosol method
Authors:
Ghitulica, C; Cernea, M; Vasile, BS; Andronescu, E; Vasile, OR; Dragoi, C; Trusca, R
Published: JUL 2013, CERAMICS INTERNATIONAL, 39, 5930, DOI: 10.1016/j.ceramint.2013.01.015
[(Bi0.5Na0.5)TiO3](0.92)-[BaTiO3](0.08) lead free piezoelectric materials were prepared by the pyrosol method. The as-obtained powder shows spherical grains of various sizes, composed of crystallites of about 10 nm. NBT-BT0.08 ceramic obtained at 700 degrees C show rhombohedral NBT as the main phase and traces of hexagonal Bi2O3 as secondary phase. The ceramics prepared from this powder and sintered at 1000 and 1100 degrees C are single phase with good dielectric and ferroelectric properties. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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