Defects and physicomechanical properties of polycrystalline β-rhombohedral boron

Darsavelidze, G.; Tsagareishvili, Otar; Eterashvili, Tamaz; Metreveli, V. Sh.; Tavadze, G. F.; Khomeriki, D.I.

doi:10.1016/0022-5088(86)90031-7

Cited by 11 publications

(5 citation statements)

References 2 publications

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“…But neither some additional weaker anomalies at lower and at higher temperatures nor particularly the strong anisotropy stated by these authors [33] have been confirmed by our own results or by those of other authors to be discussed. The softening of the structure in the temperature range around 500 to 600 K is additionally confirmed by the temperature dependent internal friction (typical curves reproduced from [34] and [35] in Fig. 10).…”

Section: Discussionsupporting

confidence: 64%

Interband and Gap State Related Transitions in β‐Rhombohedral Boron

Werheit

Laux

Kuhlmann

1993

Physica Status Solidi (b)

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The anisotropy of the electronic interband transitions of 0-rhombohedra1 boron is determined by optical absorption measurements. The band gaps (indirect allowed transitions) are 1.32(1) and 1.50(1) eV for E 11 c, respectively, 1.29(1) and 1.46(1) eV for E I c (extrapolated to T = 0 K). At low temperatures these gaps decrease, while the thermal equilibrium develops. The temperature dependence of the gap isattributed to the thermaldisorder caused byphonons of 121.9(E 11 c)and 94.1 meV(E I c) representing the most prominent intraicosahedral vibrations. Six intrinsic trapping levels for electrons in distances between 0.17 and 1.15 eV from the conduction band edge are determined, the closer ones in agreement with different photo effects. The trapping levels are attributed to distortion states of the icosahedra due to a dynamical Jahn-Teller effect. This conception allows the interpretation of other physical properties like internal friction, discontinuities of thermal expansion, and electrical conductivity, of the temperature dependence of the ESR linewidth, and of the density of paramagnetic centers (spin density and magnetic susceptibility).Die Anisotropy der elektronischen Interbandubergange des P-rhomboedrischen Bors wurde aus der optischen Absorption bestimmt. Die Bandabstande (indirekt erlaubte Ubergange) betragen, extrapoliert auf T = 0 K, 1,32(1) und 1,50(l)eV fur E 11 c bzw. 1,29(1) und 1,46(l)eV fur E l c. Bei tiefen Temperaturen nehmen die Bandabstande im Verlauf der Einstellung des thermischen Gleichgewichtes ab. Der Temperaturgang der Bandabstande wird der temperaturbedingten Fehlordnung des Gitters durch die thermische Anregung der starksten intraikosaedrischen Phononen bei 121.9 ( E 1) c) und 94,l meV ( E i c) zugeordnet. Sechs intrinsische Haftniveaus fur Elektronen in Ahtanden zwischen 0,17 und 1,15 eV vom Leitungsband werden nachgewiesen, die bandnahen sind in Ubereinstimmung mit verschiedenen Photoeffekten. Die Haftniveaus werden Verzerrungszustanden der Ikosaeder infolge eines dynamischen Jahn-Teller-Effektes zugeschrieben. Diese Konzeption erlaubt die Erklirung anderer physikalischer Eigenschaften wie der inneren Reibung, der Diskontinuitaten der thermischen Dilatation und der elektrischen Leitfahigkeit, der Temperaturabhangigkeit der ESR-Linienbreite sowie der Konzentration lokalisierter paramagnetischer Zentren (Spindichte und magnetische Suszeptibilitat).

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Section: Discussionsupporting

confidence: 64%

Interband and Gap State Related Transitions in β‐Rhombohedral Boron

Werheit

Laux

Kuhlmann

1993

Physica Status Solidi (b)

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“…Our experiments clearly established that both phases are present in high purity (99.2%) samples of boron, with each grain being fully β or fully τ. Highly twinned structures have been observed previously [1] as have observations that twinning decreases as the high purity β-B grows from the liquids [2]. However, our Letter focuses on identifying a new crystal phase that we discovered experimentally, τ-B, determining its crystal structure that matches our experimental diffraction pattern and elucidating the nature of this new phase using DFT.…”

mentioning

confidence: 65%

Erratum: New Ground-State Crystal Structure of Elemental Boron [Phys. Rev. Lett. 117 , 085501 (2016)]

An¹,

Reddy²,

Xie³

et al. 2017

Phys. Rev. Lett.

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“…In 1993, Werheit, Laux, and Kuhlman reported on the detail of the optical absorption and its relaxation behavior, and from this they interpreted the anomalies observed in various physical quantities at around T = 500–600 K, including the internal-friction peaks, elastoresistance, thermal expansion, electrical conductivity, thermal conductivity, and EPR. ,,, Although it is not clear if all of those observations share the same origin, the POS-hopping mechanism reported in 2010 might be responsible for some of the anomalies, but further investigations are needed to come to robust conclusions.…”

Section: Anomalous Properties Of β-Rhombohedral Boronmentioning

confidence: 99%