Carbon in boron carbide: The crystal structure of B11.4C3.6

Коновалихин, С. В.; Ponomarev, V. I.

doi:10.1134/s0036023609020053

Cited by 44 publications

(22 citation statements)

References 22 publications

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“…The magnitude of all further maxima in the difference ED (in all crystals) was found to be at the noise level of the Fourier series summation. The information obtained from our structure refinements suggested different deviations from the ideal structural motif in different crystals being in agreement with the results of other studies …”

Section: Figuresupporting

confidence: 92%

Local Atomic Arrangements and Band Structure of Boron Carbide

Rasim

Ramlau²,

Leithe‐Jasper³

et al. 2018

Angewandte Chemie

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Boron carbide,the simple chemical combination of boron and carbon, is one of the best-known binary ceramic materials.D espite that, ac oherent description of its crystal structure and physical properties resembles one of the most challenging problems in materials science.B yc ombining ab initio computational studies,p recise crystal structure determination from diffraction experiments,a nd state-of-the-art high-resolution transmission electron microscopyimaging,this concerted investigation reveals hitherto unknown local structure modifications together with the knowns tructural alterations.T he mixture of different local atomic arrangements within the real crystal structure reduces the electron deficiency of the pristine structure CBC + B 12 ,a nswering the question about electron precise character of boron carbide and introducing new electronic states within the band gap,w hicha llow abetter understanding of physical properties.The binary phase in the system boron-carbon, with al arge and temperature-dependent complex shape of the homogeneity range between 8.6 and 18.8 at %ofcarbon, is known as boron carbide. [1,2] Preparation difficulties and the complexity of the phase diagram are the reasons why in earlier publications even two separated phases in this compositional region were described. [3] First observed at the end of the 19th century as ab y-product during the reduction of boron oxide with carbon or magnesium (in carbon vessels), [4,5] boron carbide has continued to attract the attention of researchers and engineers for decades owing to its mechanical and thermal properties.The Vickers hardness and fracture toughness approaching the properties of diamond are the reason for the nickname "black diamond" and for application as lightweight protection. [6] Furthermore,boron carbide shows good properties against neutrons,s tability to extreme temperatures,i onizing radiation and most chemicals,a ll combined with al ow density.C onsequently,m ultiple applications of materials based on this substance were implemented since the middle of the 20th century.The fascination for this material is still so strong that it has even been supposed to be ah ightemperature superconductor. [7] Later, the thermoelectric properties of boron carbide came into the focus of researchers owing to the demand for efficient thermoelectric materials for high-temperature applications, [8][9][10][11][12][13] including the manufacturing of thermoelectric modules with boron carbide as the ptype material. [14] To understand the intrinsic reasons for the good thermoelectric performance,c entimeter-sized single crystals of this material were grown utilizing floating-zone technology. [15] In agreement with earlier results,t hese crystals show apositive Seebeck coefficient, that is,p-type semiconducting behavior (Supporting Information, Figure S1, top). Another group of boron cage compounds,the rare-earth borocarbonitrides RB 15.5 CN,R B 22 C 2 N, and Y 1Àx B 28.5 C 4 ,w as suggested as an-type boride-based counterpart to boron carbide. [16] Durin...

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Section: Figuresupporting

confidence: 92%

Local Atomic Arrangements and Band Structure of Boron Carbide

Rasim

Ramlau²,

Leithe‐Jasper³

et al. 2018

Angewandte Chemie

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“…1(a). Even though synthesis of boron carbide beyond the carbon-rich limit has been reported one time, ∼24 at.% C by Konovalikhin et al [24], synthesizing boron carbide, where at.% C 20, generally results in a mixture of boron carbide and free graphitelike carbon [11,25,26]. Recently, Jay et al [27] suggested a possibility that the solubility range of boron carbide could be extended to 21.43 at.% C, in which, instead of the three-atom C-B-C chain, a structural model of B 11 C p (C-C), as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…Although boron carbide has been intensively studied both experimentally and theoretically, there are still unresolved questions, debatable among the researchers, regarding the maximum at.% C [1,11,12,21,24,27,28], the extent of configurational disorder [22,23,29,30], the electronic band gap [15,22,[31][32][33][34][35], and stability under high pressure [31,[36][37][38][39], thus deserving further investigation. Recent theoretical studies of boron carbide [22,23,29,40] demonstrated that configurational disorder of boron and carbon atoms on the different lattice positions, activated at elevated temperatures, determines several properties.…”

Section: Introductionmentioning

confidence: 99%

Carbon-rich icosahedral boron carbides beyondB4Cand their thermodynamic stabilities at high temperature and pressure from first principles

2016

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We investigate the thermodynamic stability of carbon-rich icosahedral boron carbide at different compositions, ranging from B 4 C to B 2 C, using first-principles calculations. Apart from B 4 C, generally addressed in the literature, B 2.5 C, represented by B 10 C p 2 (C-C), where C p and (C-C) denote a carbon atom occupying the polar site of the icosahedral cluster and a diatomic carbon chain, respectively, is predicted to be thermodynamically stable under high pressures with respect to B 4 C as well as pure boron and carbon phases. The thermodynamic stability of B 2.5 C is determined by the Gibbs free energy G as a function of pressure p and temperature T , in which the contributions from the lattice vibrations and the configurational disorder are obtained within the quasiharmonic and the mean-field approximations, respectively. The stability range of B 2.5 C is then illustrated through the p-T phase diagrams. Depending on the temperatures, the stability range of B 2.5 C is predicted to be within the range between 40 and 67 GPa. At T 500 K, the icosahedral C p atoms in B 2.5 C configurationally disorder at the polar sites. By investigating the properties of B 2.5 C, e.g., elastic constants and phonon and electronic density of states, we demonstrate that B 2.5 C is both mechanically and dynamically stable at zero pressure, and is an electrical semiconductor. Furthermore, based on the sketched phase diagrams, a possible route for experimental synthesis of B 2.5 C as well as a fingerprint for its characterization from the simulations of x-ray powder diffraction pattern are suggested.

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“…Boron is known to have a huge neutron capture cross-section, 3800 barns [42], and this particular crystal has a B atomic density of 11.4×10 23 cm −3 , which is 3 times larger than boron carbide [43], A crystal from the XYB 14 family that is chemically doped could act both as the neutron capture medium and as the electronics used to measure the deposited energy. Such a medium could find direct use in existing detector designs, and may allow for improvement of these devices by increasing their overall efficiencies [44,45,46,47,48].…”

Section: Resultsmentioning

confidence: 99%

The electronic and mechanical properties of the XYB14 complex borides studied by first-principles methods

Wan

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The effect of C substitution in the AlLiB 14 lattice is examined using first-principles methods. The inter-icosahedra B site is found to be the most favorable B site for C substitution and the formation energy is predicted to be 1.7 eV in B-rich conditions. Substituting C does not affect the band gap, nor does it introduce defect states to the gap. An ideal brittle cleavage model is used to study the impact of C doping on the mechanical properties of AlLiB 14 and it is concluded that introducing C to the crystal decreases the ideal fracture strength by 3.3 GPa, which is about a 12% reduction in overall strength.

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Carbon in boron carbide: The crystal structure of B11.4C3.6

Cited by 44 publications

References 22 publications

Local Atomic Arrangements and Band Structure of Boron Carbide

Local Atomic Arrangements and Band Structure of Boron Carbide

Carbon-rich icosahedral boron carbides beyondB4Cand their thermodynamic stabilities at high temperature and pressure from first principles

The electronic and mechanical properties of the XYB14 complex borides studied by first-principles methods

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