Phase transition in β-rhombohedral boron near 550 K

Hoffmann, Stefan; Werheit, H.

doi:10.1016/j.solidstatesciences.2012.01.025

Cited by 12 publications

(12 citation statements)

References 18 publications

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“…Then the temperature difference T T od dh turns to the driving force of the transition. Moving B atoms may not be at all ruled out for boron-rich crystals; in β-rhombohedral boron, it is currently speculated that B atoms migrate at a moderate temperatures [43,44]. Hence, it is reasonable that the motion of H atoms enhances the migration of B atoms.…”

Section: Transition Mechanism: An Order-disorder Transition By Coopermentioning

confidence: 99%

Hydrogenation, dehydrogenation of α-tetragonal boron and its transition to δ-orthorhombic boron

Uemura¹,

Shirai²,

Kunstmann³

et al. 2019

J. Phys. Mater.

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Boron bulk crystals are marked by exceptional structural complexity and unusual related physical phenomena. Recent reports of hydrogenated α-tetragonal and a new δ-orthorhombic boron B 52 phase have raised many fundamental questions. Using density functional theory calculations it is shown that hydrogenated α-tetragonal boron has at least two stable stoichiometric compositions, B 51 H 7 and B 51 H 3 . Thermodynamic modeling was used to qualitatively reproduce the two-step phase transition reported by (Ekimov et al 2016 J. Mater. Res. 31, 2773) upon annealing, which corresponds to successive transitions from B 51 H 7 to B 51 H 3 to pure B 52 . The so obtained δ-orthorhombic boron is an ordered, low-temperature phase and α-tetragonal boron is a disordered, high-temperature phase of B 52 . The two phases are connected by an order-disorder transition, that is associated with the migration of interstitial boron atoms. Atom migration is usually suppressed in strongly bound, covalent crystals. It is shown that the migration of boron atoms is likely to be assisted by the migration of hydrogen atoms upon annealing. These results are in excellent agreement with the above mentioned experiment and they represent an important step forward for the understanding of boron and hydrogenated boron crystals. They further open a new avenue to control or remove the intrinsic defects of covalently bound crystals by utilizing volatile, foreign atoms.

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Section: Transition Mechanism: An Order-disorder Transition By Coopermentioning

confidence: 99%

Hydrogenation, dehydrogenation of α-tetragonal boron and its transition to δ-orthorhombic boron

Uemura¹,

Shirai²,

Kunstmann³

et al. 2019

J. Phys. Mater.

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“…Boron and borides are considered to be promising thermoelectric (TE) materials for use at high temperatures of more than 1300 K [1][2][3][4][5][6], however, their properties still need to be developed further to enable practical use. Regarding elemental boron, the structure of βrhombohedral (β-rh) B (space group m R3 ) [7][8][9][10][11] has been extensively studied with respect to its ability to accommodate interstitially different kinds of foreign atoms [12][13][14]. It has been shown that metal doping into β-rh B can control the bonding nature in and between the clusters, delivering variation of physical properties such as electrical and thermal conductivities and Seebeck coefficient [13,[15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

“…, z=0.1350(2) 1.0; 0.0066(9) B13 in 18h (x, x ,z) occ. ; U eqx=0.6110(3), z=0.2766(2) 0.642(10); 0.013(1) x=0.6104(5), z=0.2769(4) 0.70(2); 0.014(2) B11 in 18h (x, x ,z) occ. ; U eqx=0.7239(2), z=0.1604(1) 1.0; 0.0083(6) dx=0.7238(3), z=0.1599(2) 1.0; 0.0084(10) B12 in 18h (x, x ,z) occ.…”

mentioning

confidence: 99%

“…; U eqx=0.6110(3), z=0.2766(2) 0.642(10); 0.013(1) x=0.6104(5), z=0.2769(4) 0.70(2); 0.014(2) B11 in 18h (x, x ,z) occ. ; U eqx=0.7239(2), z=0.1604(1) 1.0; 0.0083(6) dx=0.7238(3), z=0.1599(2) 1.0; 0.0084(10) B12 in 18h (x, x ,z) occ. ; U eqx=0.7570(2), z=0.2305(1) 1.0; 0.0058(6) x=0.7568(3), z=0.2307(2) 1.0; 0.0061(10) B14 in 6c (0,0,z) occ.…”

mentioning

confidence: 99%

“…; U eq 1.0; 0.018(2) e 1.0; 0.014(3) Zr2 in 18h (x, x ,z) (D) occ. ; U eqx=0.53595(4), z=0.34227(3) 0.299(2); 0.0072(3)x=0.53605(10), z=0.34248(7) 0.306(2); 0.0088(5) Zr3 in 6c (0,0,z) (E) occ. ; U eq z=0.26437(5) 0.333(2); 0.0040(4) z=0.26426(10) 0.345(4); 0.0043(7) Zr44 in 18g (x,0,½) (F) occ.…”

mentioning

confidence: 99%

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Zr doped β-rhombohedral boron: Widely variable Seebeck coefficient and structural properties

et al. 2017

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The doping effect of zirconium on the structure, Seebeck coefficient and electrical resistivity of β-rhombohedral B was studied for the metal rich concentration range Zr x B 100-x , 1.88x2.75. Structural studies proved the Zr atoms mainly in E and D voids for the metal rich compositions, and also elucidated the minor Zr occupancies of the N, F and A 1 holes. Seebeck coefficients were effectively shifted within a wide range of positive and negative values by varying the Zr content (p-type: S max ~ +420 µVK-1 at 673 K for x=1.88; n-type: S max ~-670 VK-1 at 473 K for x=2.74). Electrical resistivities generally followed the Mott's relation for the variable-range hopping. Excellent compositional agreement has been observed between structural and thermoelectric properties discontinuities.

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ChemInform Abstract: Phase Transition in β‐Rhombohedral Boron Near 550 K.

Hoffmann

Werheit

2013

ChemInform

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Phase Transition in β-Rhombohedral Boron Near 550 K. -Differential scanning calorimetry indicates a structural phase transition of high-purity single crystal β-rhombohedral boron close to 550 K. This transition is responsible for discontinuities of numerous physical properties in this temperature range, which are interpreted assuming site hopping of boron atoms between regular, partially occupied crystallographic sites. -(HOFFMANN, S.; WERHEIT*, H.; Solid State Sci. 14 (2012) 11-12, 1572-1577, http://dx.

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Phase transition in β-rhombohedral boron near 550 K

Cited by 12 publications

References 18 publications

Hydrogenation, dehydrogenation of α-tetragonal boron and its transition to δ-orthorhombic boron

Hydrogenation, dehydrogenation of α-tetragonal boron and its transition to δ-orthorhombic boron

Zr doped β-rhombohedral boron: Widely variable Seebeck coefficient and structural properties

ChemInform Abstract: Phase Transition in β‐Rhombohedral Boron Near 550 K.

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