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Title: Synthesis, structure, and properties of BaAl(sub 2)Si(sub 2).

Abstract

No abstract prepared.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
National Science Foundation (NSF)
OSTI Identifier:
928644
Report Number(s):
ANL/IPNS/JA-58451
Journal ID: ISSN 0020-1669; INOCAJ; TRN: US200812%%316
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Inorg. Chem.; Journal Volume: 46; Journal Issue: 11 ; May 28, 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
36 MATERIALS SCIENCE; SYNTHESIS; MICROSTRUCTURE; CHEMICAL PROPERTIES; PHYSICAL PROPERTIES; ALUMINIUM SILICIDES; BARIUM COMPOUNDS; SILICIDES

Citation Formats

Condron, C. L., Hope, H., Piccoli, P. M. B., Schultz, A. J., Kauzlarich, S. M., Intense Pulsed Neutron Source, and Univ. of California. Synthesis, structure, and properties of BaAl(sub 2)Si(sub 2).. United States: N. p., 2007. Web. doi:10.1021/ic070078h.
Condron, C. L., Hope, H., Piccoli, P. M. B., Schultz, A. J., Kauzlarich, S. M., Intense Pulsed Neutron Source, & Univ. of California. Synthesis, structure, and properties of BaAl(sub 2)Si(sub 2).. United States. doi:10.1021/ic070078h.
Condron, C. L., Hope, H., Piccoli, P. M. B., Schultz, A. J., Kauzlarich, S. M., Intense Pulsed Neutron Source, and Univ. of California. Mon . "Synthesis, structure, and properties of BaAl(sub 2)Si(sub 2).". United States. doi:10.1021/ic070078h.
@article{osti_928644,
title = {Synthesis, structure, and properties of BaAl(sub 2)Si(sub 2).},
author = {Condron, C. L. and Hope, H. and Piccoli, P. M. B. and Schultz, A. J. and Kauzlarich, S. M. and Intense Pulsed Neutron Source and Univ. of California},
abstractNote = {No abstract prepared.},
doi = {10.1021/ic070078h},
journal = {Inorg. Chem.},
number = 11 ; May 28, 2007,
volume = 46,
place = {United States},
year = {Mon May 28 00:00:00 EDT 2007},
month = {Mon May 28 00:00:00 EDT 2007}
}
  • Three solid solutions with the general formula AEAl{sub 4−x}Ge{sub x} (AE=Eu, Sr, Ba; 0.32(1)≤x≤0.41(1)) have been synthesized via the aluminum self-flux method, and their crystal structures have been established from powder and single-crystal X-ray diffraction. They are isotypic and crystallize with the well-known BaAl{sub 4} structure type, adopted by the three AEAl{sub 4} end members. In all structures, Ge substitutes Al only at the 4e Wyckoff site. Results from X-rays photoelectron spectroscopy on EuAl{sub 4−x}Ge{sub x} and EuAl{sub 4} indicate that the interactions between the Eu{sup 2+} cations and the polyanionic framework are enhanced in the Ge-doped structure, despite themore » slightly elevated Fermi level. Magnetic susceptibility measurements confirm the local moment magnetism, expected for the [Xe]4f{sup 7} electronic configuration of Eu{sup 2+} and suggest strong ferromagnetic interactions at cryogenic temperatures. Resistivity data from single-crystalline samples show differences between the title compounds, implying different bonding characteristics despite the close Debye temperatures. A brief discussion on the observed electron count and homogeneity ranges for AEAl{sub 4−x}Ge{sub x} (AE=Eu, Sr, Ba) is also presented. - Graphical abstract: AEAl{sub 4−x}Ge{sub x} (AE=Eu, Sr, Ba; 0.32(1)≤x≤0.41(1)), three “electron-rich” phases with BaAl{sub 4} structure type have been synthesized and characterized. Display Omitted - Highlights: • Three BaAl{sub 4}-type ternary aluminum germanides have been synthesized with Eu, Sr and Ba. • Eu, Sr and Ba cations have no apparent influence on the solubility of Ge. • The Ge atoms substitute Al on one of two framework sites, thereby strengthening the interactions between the cations and the polyanionic framework.« less
  • Highlights: Black-Right-Pointing-Pointer The brightness of Si-N-doped BHA phosphor is 119.9% of the un-doped BHA. Black-Right-Pointing-Pointer The decay time of Si-N-doped BHA phosphor is shorter than the un-doped sample. Black-Right-Pointing-Pointer The Si-N doping BHA is expected to be potentially applicable to 3D PDPs. -- Abstract: Si-N-doped BaAl{sub 12}O{sub 19}:Mn{sup 2+} phosphors were synthesized by a conventional solid-state reaction. It reveals that an efficiently host absorption in the vacuum ultraviolet region, which could be ascribed to the restricted Reidinger defects and oxygen vacancies by the Si-N doping. A fortified energy transfer from host to the activators was observed because of the newlymore » formed defect energy levels which generated from the un-equivalence substitution of Si-N for Al-O. The shorter decay time of 4.05 ms was obtained which due to the increased defect concentration. This result indicates that Si-N doping BaAl{sub 12}O{sub 19}:Mn{sup 2+} phosphors would meet the requirements of 3D PDPs.« less
  • Doubly [SiMe{sub 2}]-bridged metallocenes (1,2-SiMe{sub 2}){sub 2}{l{underscore}brace}{eta}{sup 5}-C{sub 5}H{sub 2}-4-R{r{underscore}brace}{l{underscore}brace}{eta}{sup 5}-C{sub 5}H-3,5-(CHMe{sub 2}){sup 2}{r{underscore}brace}ZrCl{sub 2} (R = H (1a), CHMe{sub 2} (1b), SiMe{sub 3} (1c), CHMe(CMe{sub 3}) (1d), (+)-menthyl (1e)), when activated by methylaluminoxane (MAO), catalyze propylene polymerization with high activities. The preparations and X-ray structures of the dilithio salt of an enantiopure, doubly silylene-bridged bis(cyclopentadienyl)ligand, Li{sub 2}[(1,2-Me{sub 2}Si){sub 2}-{l{underscore}brace}C{sub 5}H{sub 2}-4-(1R,2S,5R-menthyl){r{underscore}brace}{l{underscore}brace}(C{sub 5}H-3,5-(CHMe{sub 2}){sub 2}){r{underscore}brace}]{center{underscore}dot}3THF, as well as the corresponding zircononcene dichloride, [(1,2-Me{sub 2}Si){sub 2}{l{underscore}brace}{eta}{sup 5}-C{sub 5}H{sub 2}-4-(1R,2S,5R-menthyl){r{underscore}brace}{l{underscore}brace}{eta}{sup 5}-C{sub 5}H-3,5-(CHMe{sub 2}){sub 2}{r{underscore}brace}]ZrCl{sub 2}(1e), are reported. The C{sub s}-symmetric systems 1a-c are highly regiospecific and syndiospecific (> 99.5%) in neat propylene.more » At lower propylene concentrations, polymers with lower molecular weights and tacticity (mostly m-type stereoerrors) are obtained. The microstructures of polymers produced under differing reaction conditions are consistent with stereocontrol dominated by a site epimerization process, an inversion of configuration at zirconium resulting from the polymer chain swinging from one side of the metallocene wedge to the other without monomer insertion. The relative importance of chain epimerization (at the {beta} carbon) has been established by parallel polymerization of 2-d{sub 1}-propylene and d{sub 0}-propylene with 1b/MAO at low propylene concentrations. The C{sub 1}-symmetric systems 1d,e/MAO display an unusual dependence of stereospecificity on propylene concentration, switching from isospecific to syndiospecific with increasing propylene pressure, consistent with a competitive unimolecular site epimerization process and a bimolecular chain propagation. The microstructures of the polypropylenes produced by 1d/MAO and 1e/MAO with [r] {approx} 50% resemble the hemiisotactic microstructure produced by Me{sub 2}C({eta}{sup 5}-C{sub 5}H{sub 3}-3-Me)({eta}{sup 5}-C{sub 13}H{sub 8})ZrCl{sub 2} (2b)/MAO. Contrastingly, the hemiisotactic polypropylene microstructure obtained with 2b/MAO is found to be maintained at all propylene concentrations examined.« less
  • Some aspects of the structures of the anion nets in the CaAl{sub 2}Si{sub 2} and BaAl{sub 4} structure types are investigated by using the techniques of tight-binding theory. The authors examine the factors that stabilize main-group compounds that adopt AlB{sub 2}, CaIn{sub 2}, and CaAl{sub 2}Si{sub 2} structures types for similar electron counts, i.e., the half-filled band. Traditional molecular orbital concepts and the method of moments are combined to compare the two structural isomers CaAl{sub 2}Si{sub 2} and BaAl{sub 4}. Furthermore, we utilize two-dimensional pieces of these two structures as fundamental building blocks to form other main-group compounds.
  • Two sol-gel routes have been used to prepare celsian (BaAl{sub 2}Si{sub 2}O{sub 8}) precursors. The crystallization behaviors of unseeded gels and the gels seeded with 5 wt% feldspar, rutile, LiAlSi{sub 3}O{sub 8}, and ZrO{sub 2} crystals as well as SrAl{sub 2}Si{sub 2}O{sub 8} gel have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermal gravimetric and differential thermal analyses (TGA and DTA). It was found that metastable hexacelsian, rather than the preferred monoclinic celsian, was the major crystallization product in the two unseeded gels. Seeding largely enhanced the crystallization of monoclinic celsian, but the mechanisms involved weremore » different for seeding with different crystals. SrAl{sub 2}Si{sub 2}O{sub 8} gel and ZrO{sub 2} crystals acted as normal heterogeneous centers and had little catalytic effect on monoclinic celsian crystallization. Feldspar and rutile crystals worked as epitaxial substrates for monoclinic celsian and produced pure monoclinic celsian in some temperature regions. LiAlSi{sub 3}O{sub 8} seeds lowered the glass transition temperature of the immediately adjacent gel matrix and led to the crystallization of pure monoclinic celsian.« less