The Crystal Structure of B2.89Si.

Magnusson, Bengt; Brosset, Cyrill; Seleborg, Madeleine; Motzfeldt, K.; Theander, Olof; Flood, H.

doi:10.3891/acta.chem.scand.16-0449

Cited by 64 publications

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“…There are two crystallographically distinct Si atoms one at the apex of the fused triangles (Si(1)) and one that forms the base with its symmetry equivalent (Si(2)). The Si(1)ÀSi(1) bond from apex to apex is 2.3336 (8) . The other SiÀSi bonds in the structure are substantially longer with Si(1)ÀSi(2) being 2.5967(4) and Si(2)ÀSi(2) (base of the triangle) at 2.3970 (8) .…”

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confidence: 97%

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Stabilization of β‐SiB₃ from Liquid Ga: A Boron‐Rich Binary Semiconductor Resistant to High‐Temperature Air Oxidation

Salvador

Bilc²,

Mahanti³

et al. 2003

Angewandte Chemie

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Liquid metals can be powerful solvents for the exploration of novel refractory solid-state materials ranging from intermetallic compounds to silicides, carbides and borides. Recently we have discovered, from liquid Al and Ga, a large variety of ternary and quaternary phases of the type RE/TM/Si or Ge, RE/TM/Al or Ga, RE/TM/Al/Si or Ge, and RE/TM/Ga/Ge or Si (RE = rare earth La-Lu, and TM = 1st, 2nd, or 3rd row transition metal). [1,2] Many of these phases cannot be formed by conventional high temperature solid-state synthetic techniques such as direct combination reactions with arc melting or radio-frequency (rf) induction furnace heating. [3] We have extended the flux methodology to include RE/TM/B/Si (borosilicides) in an attempt to produce lighter analogues of the RE/TM/Al/Si compounds, and we chose liquid gallium as the reaction medium because both Si and B are soluble in it and do not form binaries.[4] Also from previous work we learned that RE/TM/Ga/Si phases do not form readily, and so competing phases of this type are not anticipated.[1] Boroncontaining solids have acquired renewed interest because quaternary borocarbides are superconducting, [5] and MgB 2 is a high temperature nonoxidic superconductor. [6] Borosilicides are an unfamiliar class of compounds. Specifically boron-rich borosilicides are rare with only a handful of examples are known: CrSi 3 (B 12 )Se 12 (B 2 Se 3 ) 1.33 , REB 41 Si 1.2 (RE = Y, Tb), Sc 0.83Àx B 10.0Ày C 0.17+y Si 0.083Àz , [7] SiB 3 , SiB 4 and SiB 6[8] to name a few. We have recently shown that liquid gallium can provide an excellent route to complex quaternary silicon borides such as Tb 1.8 Si 8 C 2 (B 12 ) 3 that cannot be formed by using high-temperature techniques such as arc melting.[9] Herein, we present an illustration of the ability of liquid Ga to stabilize boride phases inaccessible by conventional synthetic routes. Namely, we describe a novel B-rich, refractory, semiconducting binary phase b-SiB 3 .b-SiB 3 is a surprising discovery because a phase with a similar formula, Si 1Àx B 3+x with a compositional spread of x = 0-0.2, [10] that has a rhombohedral structure has been known for decades.[11] We will henceforth refer to this phase as aSiB 3 . Instead b-SiB 3 is orthorhombic Imma, representing a new structure type.[12] Despite the similarity in stoichiometry and the presence of B 12 icosahedra the structural features and electronic properties of the a and b phases are very different. Rhombohedral a-SiB 3 forms from direct combination of the elements with prolonged isothermal heating at 1225 8C or by arc melting, in contrast b-SiB 3 was produced from a lower temperature reaction (1000-850 8C) in Ga flux. Additionally, in a-SiB 3 , some Si atoms are randomly distributed in the B 12 cages resulting in very distorted icosahedra. [13] In contrast, Si atoms in b-SiB 3 are rigorously excluded from the cages, thus resulting in more regular icosahedra. To the best of our knowledge this is the first Si-B binary phase that is fully crystallographically ordered without any ...

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confidence: 97%

“…The Si(1)ÀSi(1) bond from apex to apex is 2.3336 (8) . The other SiÀSi bonds in the structure are substantially longer with Si(1)ÀSi(2) being 2.5967(4) and Si(2)ÀSi(2) (base of the triangle) at 2.3970 (8) . To the best of our knowledge, the infinite Si 4 chain is a novel structural feature, although it has a slight similarity to the Ge 4 chains of BaGe 2 .…”

mentioning

confidence: 97%

Stabilization of β‐SiB₃ from Liquid Ga: A Boron‐Rich Binary Semiconductor Resistant to High‐Temperature Air Oxidation

Salvador

Bilc²,

Mahanti³

et al. 2003

Angewandte Chemie

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“…[204] There has long been no doubt, [205] however, that the structure is based on a-B with a Si 2 group, and that the high silicon content and the relatively large lattice parameters are due to partial incorporation of silicon atoms into the polar position of the icosahedron.…”

Section: General Observationsmentioning

confidence: 99%

Boron: Elementary Challenge for Experimenters and Theoreticians

Albert¹,

Hillebrecht²

2009

Angew Chem Int Ed

580

436

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Many of the fundamental questions regarding the solid-state chemistry of boron are still unsolved, more than 200 years after its discovery. Recently, theoretical work on the existence and stability of known and new modifications of the element combined with high-pressure and high-temperature experiments have revealed new aspects. A lot has also happened over the last few years in the field of reactions between boron and main group elements. Binary compounds such as B(6)O, MgB(2), LiB(1-x), Na(3)B(20), and CaB(6) have caused much excitement, but the electron-precise, colorless boride carbides Li(2)B(12)C(2), LiB(13)C(2), and MgB(12)C(2) as well as the graphite analogue BeB(2)C(2) also deserve special attention. Physical properties such as hardness, superconductivity, neutron scattering length, and thermoelectricity have also made boron-rich compounds attractive to materials research and for applications. The greatest challenges to boron chemistry, however, are still the synthesis of monophasic products in macroscopic quantities and in the form of single crystals, the unequivocal identification and determination of crystal structures, and a thorough understanding of their electronic situation. Linked polyhedra are the dominating structural elements of the boron-rich compounds of the main group elements. In many cases, their structures can be derived from those that have been assigned to modifications of the element. Again, even these require a critical revision and discussion.

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“…Die extrem hohe chemische und thermische Stabilität der Siliciumboride erschwert die analytische Charakterisierung. [204] Schon lange gilt jedoch als unumstritten, [205] [188] Die Mikrohärte von B 6 O wird mit 38 GPa angegeben und die Bandlücke von B 6 O soll 2 eV betragen. [189][190][191] Elektronen-und Röntgenbeugungsuntersu-chungen bestätigten ältere Untersuchungen, und die rasterelektronemikroskopischen Aufnahmen der Kristalle zeigen die einspringenden Ecken eines ikosaedrisch verzwillingten Kristalls, der aus zwanzig Zwillingsindividuen bestehen soll.…”

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Bor – elementare Herausforderung für Experimentatoren und Theoretiker

Albert

Hillebrecht

2009

Angewandte Chemie

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Auch mehr als zweihundert Jahre nach der Entdeckung des Elementes Bor gibt es auf viele grundlegende Fragen in der Festkörperchemie von Bor noch keine eindeutigen Antworten. In jüngster Zeit zeigten theoretische Arbeiten zur Stabilität und Existenz bekannter und neuer Modifikationen des Elements in Verbindung mit Hochdruck‐ und Hochtemperaturexperimenten neue Aspekte. Auch auf dem Gebiet der Reaktionen von Bor mit Hauptgruppenelementen hat sich in den letzten Jahren viel getan. Aufsehen haben binäre Verbindungen wie B6O, MgB2, LiB1−x, Na3B20 oder CaB6 erregt, aber auch die elektronenpräzisen, farblosen Boridcarbide Li2B12C2, LiB13C2 und MgB12C2 sowie Graphit‐analoges BeB2C2 verdienen besonderes Augenmerk. Physikalische Eigenschaften wie Härte, Supraleitfähigkeit, Neutroneneinfangquerschnitt und Thermoelektrizität machen borreiche Verbindungen auch für Materialforschung und Anwendung attraktiv. Die größten wissenschaftlichen Herausforderungen bestehen jedoch weiterhin in der Synthese einphasiger Produkte in makroskopischen Mengen und in Form von Einkristallen, in der zweifelsfreien Identifizierung und Bestimmung von Zusammensetzung und Kristallstruktur sowie im Verständnis der elektronischen Situation. Verknüpfte Polyeder sind das dominierende Strukturelement in borreichen Verbindungen der Hauptgruppenelemente. In vielen Fällen leiten sich deren Strukturen von denen ab, die den Elementmodifikationen zugeschrieben werden. Auch diese bedürfen allerdings einer neuen, kritischen Durchsicht und Diskussion.

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The Crystal Structure of B2.89Si.

Cited by 64 publications

References 0 publications

Stabilization of β‐SiB₃ from Liquid Ga: A Boron‐Rich Binary Semiconductor Resistant to High‐Temperature Air Oxidation

Stabilization of β‐SiB₃ from Liquid Ga: A Boron‐Rich Binary Semiconductor Resistant to High‐Temperature Air Oxidation

Boron: Elementary Challenge for Experimenters and Theoreticians

Bor – elementare Herausforderung für Experimentatoren und Theoretiker

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The Crystal Structure of B2.89Si.

Cited by 64 publications

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Stabilization of β‐SiB3 from Liquid Ga: A Boron‐Rich Binary Semiconductor Resistant to High‐Temperature Air Oxidation

Stabilization of β‐SiB3 from Liquid Ga: A Boron‐Rich Binary Semiconductor Resistant to High‐Temperature Air Oxidation

Boron: Elementary Challenge for Experimenters and Theoreticians

Bor – elementare Herausforderung für Experimentatoren und Theoretiker

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Product

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Stabilization of β‐SiB₃ from Liquid Ga: A Boron‐Rich Binary Semiconductor Resistant to High‐Temperature Air Oxidation

Stabilization of β‐SiB₃ from Liquid Ga: A Boron‐Rich Binary Semiconductor Resistant to High‐Temperature Air Oxidation