Synthesis and first‐principles calculations of the structural and electronic properties of type‐I clathrates Sr8Ga16SnxGe30 − x

Li, D. C.; Li, Fang; Deng, Shukang; Kang, Kyungnam; Wei, Wen-Hou; Ruan, Haibo

doi:10.1002/pssb.201147488

Cited by 3 publications

(7 citation statements)

References 55 publications

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“…Consistent with previous theoretical results, the lattice constant of Ba 8 Ga 16 Sn 30 is higher than that of Sr 8 Ga 16 Sn 30 because of the smaller atomic radius of Sr than Ba (Table II). [20][21][22] The Yb 8 Ga 16 Sn 30 possesses a markedly larger lattice constant than Sr although the Yb atom has a smaller atomic radius than Sr, which can be ascribed to the stronger correlation interaction between Yb and framework atoms as supported by the following analysis. The formation energy E ƒ and binding energy E 0 are calculated to estimate structural stability.…”

Section: Resultsmentioning

confidence: 86%

Electronic Structure of I-M8Ga16Sn30 (M = Ba, Sr, Yb) by First-Principles Calculation

Liu

Deng

et al. 2016

Journal of Elec Materi

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Sn-based clathrates possess excellent thermoelectric properties ascribed to their higher Seebeck coefficient and lower thermal conductivity. Guest atoms significantly modulate the thermoelectric properties of Sn-based calculates because of their diverse atomic radius and interactions with framework atoms. Thus, we explored the electronic structure of I-M 8 Ga 16 Sn 30 (M = Ba, Sr, Yb) by first-principles calculation. Results revealed significant differences between Yb 8 Ga 16 Sn 30 and M 8 Ga 16 Sn 30 (M = Ba, Sr,). In particular, the Yb-filled compound substitution possesses lowest formation energy and the off-center distance of the Yb atom is the largest compared with the other structures. I-M 8 Ga 16 Sn 30 (M = Ba, Sr, Yb) is an indirect band gap semiconductor, and the enhanced hybridization effect between the guest and framework atoms' orbits exists because the Yb f orbit results in a decrease in band gap. Ba-and Srfilled clathrates have similar valence bands but slightly different conduction bands; however, Yb 8 Ga 16 Sn 30 possess the spiculate density of states near the Fermi level that reveals excellent thermoelectric properties.

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Section: Resultsmentioning

confidence: 86%

Electronic Structure of I-M8Ga16Sn30 (M = Ba, Sr, Yb) by First-Principles Calculation

Liu

Deng

et al. 2016

Journal of Elec Materi

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“…The atom site distribution among Ba,Sr in Ba 4.9 Sr 3.1 Cu 5.3 Ge 40. 7 , clearly shows that Ba,Sr atoms are sharing both centers of the cages, however, the smaller Sr-atoms reveal preference for the 2a-site in the smaller pentagondocehadral cage (occ.=0.805) with respect to a much lower Sr-occupancy of the 6c site (standardized setting) at the center of the larger tetrakaidekahedral cage (occ.=0.255). A mixed occupancy of both sites has also been found for Eu 4 Sr 4 Ga 16 Ge 30 by synchrotron X-ray powder diffraction studies [16], whereas full atom order with the smaller atom in the pentagon dodecahedron has been reported for K 6 Eu 2 Ga 10 Ge 36 [17], K 6 Eu 2 Zn 5 Ge 41 [17], K 6 Eu 2 Cd 5 Ge 41 [17] and Eu 2 Ba 6 M x Si 46-x (M=Cu, Al, Ga) [18] from X-ray single crystal data.…”

Section: Clathrates Type-i In the Systems Sr-cu-ge(sisn) And Ba-sr-cu-gementioning

confidence: 95%

“…The anisotropic displacement parameters (ADP) of the guest atoms inside the large tetrakaidecahedron are usually much larger than those of the guests inside the smaller pentagondodecahedron (see Table IV) but for Sr 8 Cu 5.3 Ge 40.7 , the ADP's of Sr2-atoms (U 11 =0.0422 (7); U 22 =U 33 =0.0802(7) Å²) were about 2 times larger applying the same structure model. Figure 3 shows a plot of the electron density of the atoms in the 6c site at 100 K (difference Fourier synthesis) illustrating a rather unitary round shape in case of Ba 4.9 Sr 3.1 Cu 5.3 Ge 40.7 (Fig.…”

Section: Clathrates Type-i In the Systems Sr-cu-ge(sisn) And Ba-sr-cu-gementioning

confidence: 97%

“…Additionally, several investigations have been published dealing with the substitution of a forth element (a) either in the framework (e.g., Sr 8 Ga 16 Ge 30-x Sn x (0  x  12) [7] and Sr 8 Al x Ga 16-x Si 30 (clathrate type-I, 0  x  7 and type-VIII, 8  x  13) [8]) or (b) as a second guest inside the cages (f. e. Ba 8-x Sr x Au 6 Ge 46-x (0  x  4) [9] and Ba 8-x Sr x Al 14 Si 32 (0.6  x  1.3) [10]).…”

Section: Introductionmentioning

confidence: 99%

“…The present work will focus on (I) the formation and crystal structure of type-I clathrates in the systems Sr-Cu-Ge(Si,Sn) and Ba-Sr-Cu-Ge; (II) on phase relations in the Ge-rich part of the Sr-Cu-Ge system at 700°C and (III) on low temperature physical properties (electrical resistivity and specific heat) of Sr 8 Cu 5.3 Ge 40. 7 . The investigations will rely on single crystal X-ray diffraction at different temperatures (300, 200, 100 K), X-ray powder diffraction, differential thermal analysis and electron probe micro analysis,…”

Section: Introductionmentioning

confidence: 99%

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Clathrate formation in the systems Sr–Cu–Ge and {Ba,Sr}–Cu–Ge

Zeiringer

Moser

Kneidinger

et al. 2014

Journal of Solid State Chemistry

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In the ternary system Sr-Cu-Ge, a clathrate type-I phase, Sr 8 Cu 5.3 Ge 40.7 (a = 1.06311(3), exists close to the Zintl limit in a small temperature interval. Sr 8 Cu 5.3 Ge 40.7 decomposes eutectoidally on cooling at 730°C into (Ge), SrGe 2 and  1 -SrCu 2-x Ge 2+x . Phase equilibria at 700°C have been established for the Ge rich part and are characterized by the appearance of only one ternary compound,  1 -SrCu 2-x Ge 2+x , which crystallizes with the ThCr 2 Si 2 structure type and forms a homogeneity range up to x=0.4 (a = 0.42850(4), c = 1.0370(1) nm).Additionally, the extent of the clathrate type-I solid solution Ba 8-x Sr x Cu y Ge 46-y (5.2  y  5.4) has been studied at various temperatures. The clathrate type-I crystal structure (space group n Pm3 ) has been proven by X-ray single crystal diffraction on two single crystals with composition Sr 8 Cu 5.3 Ge 40.7 (a = 1.06368(2) nm) and Ba 4.9 Sr 3.1 Cu 5.3 Ge 40.7 (a = 1.06748(2) nm) measured at 300, 200 and 100 K. From the temperature dependency of the lattice parameters and the atomic displacement parameters, the thermal expansion coefficients, the Debye-and Einstein-temperatures and the speed of sound have been determined.

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Structural and Electrical Transport Properties of the Type-I Clathrate Phase Ba8Ga16InxGe30-x

Wang

2013

AMR

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Thermoelectric (TE) devices are increasingly being seen as having the potential to make important contributions to reducing greenhouse gas emissions and providing cleaner forms of energy. A number of articles have been devoted to the thermoelectric properties of materials. From the search for novel and effective thermoelectric materials the clathrate structures has emerged as one of the most promising candidates for achieving very high thermoelectric figure of merit: ZT= α2σT/κ, where α, T, σ and κ are the Seebeck coefficient, absolute temperature, electrical conductivity, and total thermal conductivity, respectively [1]. For the past decade, caged clathrate compounds of group IV elements have attracted much attention because they would possess a low kL value as the theoretical minimum one, which results from rattling of atoms filled in their cages [2-3]. There are the type-I, type-III, and type-VIII structures in thermoelectric clathrates, but most compounds adopt type-I structure (space group No.223; Pm-3n). A large number of the type-I clathrates with the chemical formula of II8III16IV30 (II=Ba, Sr, Eu, III=Al, Ga, In, and IV= Si, Ge, Sn) have been synthesized and studied intensively [5-11], which results in relatively high ZT values such as 0.7 at 700 K for Ba8Ga16Ge30 and 0.87 at 870 K for Ba8Ga16Si30 [3]. Among type-I clathrates, a single-crystal n-type Ba8Ga16Ge30 grown using the Czochralski method with a ZT of 1.35 at 900 K is one of the most promising results [12].

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Synthesis and first‐principles calculations of the structural and electronic properties of type‐I clathrates Sr₈Ga₁₆Sn_xGe_30 − x

Cited by 3 publications

References 55 publications

Electronic Structure of I-M8Ga16Sn30 (M = Ba, Sr, Yb) by First-Principles Calculation

Electronic Structure of I-M8Ga16Sn30 (M = Ba, Sr, Yb) by First-Principles Calculation

Clathrate formation in the systems Sr–Cu–Ge and {Ba,Sr}–Cu–Ge

Structural and Electrical Transport Properties of the Type-I Clathrate Phase Ba<sub>8</sub>Ga<sub>16</sub>In<sub>x</sub>Ge<sub>30-x</sub>

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