Structure and properties of Ba8Ga16Ge30 clathrates by a novel synthesis method using CO gas reductive atmosphere

Matsui, Toshiyuki; Furukawa, Jyunpei; Tsukamoto, Katsuo; Tsuda, Hiroshi; Morii, K.

doi:10.1016/j.jallcom.2004.08.059

Cited by 17 publications

(6 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since E g for Ba 8 Ga 16 Ge 30 (about 0.5 eV) is significantly higher than that of the TM‐substituted clathrates,44 we can adjust the bandgaps of these TM‐substituted clathrates by forming type I clathrate solid solutions between them and Ba 8 Ga 16 Ge 30 . The solid solution approach is also expected to bring about a further reduction in the total thermal conductivity, thereby improving ZT .…”

Section: Resultsmentioning

confidence: 99%

On the Design of High‐Efficiency Thermoelectric Clathrates through a Systematic Cross‐Substitution of Framework Elements

Shi

Yang

Bai

et al. 2010

Adv Funct Materials

203

151

View full text Add to dashboard Cite

Type I clathrates have recently been identified as prospective thermoelectric materials for power generation purposes due to their very low lattice thermal conductivity values. The maximum thermoelectric figure of merit of almost all type I clathrates is, however, less than 1 and occurs at, or above, 1000 K, making them unfavorable especially for intermediate temperature applications. In this report, the Zintl–Klemm rule is demonstrated to be valid for Ni, Cu, and Zn transition metal substitution in the framework of type I clathrates and offers many degrees of freedom for material modification, design, and optimization. The cross‐substitution of framework elements introduces ionized impurities and lattice defects into these materials, which optimize the scattering of charge carriers by the substitution‐induced ionized impurities and the scattering of heat‐carrying lattice phonons by point defects, respectively, leading to an enhanced power factor, reduced lattice thermal conductivity, and therefore improved thermoelectric figure of merit. Most importantly, the bandgap of these materials can be tuned between 0.1 and 0.5 eV by adjusting the cross‐substitution ratio of framework elements, making it possible to design clathrates with excellent thermoelectric properties between 500 and 1000 K.

show abstract

Section: Resultsmentioning

confidence: 99%

On the Design of High‐Efficiency Thermoelectric Clathrates through a Systematic Cross‐Substitution of Framework Elements

Shi

Yang

Bai

et al. 2010

Adv Funct Materials

203

151

View full text Add to dashboard Cite

show abstract

“…As one kind of the most promising TE materials for the good combination of α , σ , and κ , a large number of type‐I clathrates A 8 X 16 Y 30 ( A = Ba or Sr; X = Al, Ga, or In; and Y = Si, Ge, or Sn) have been synthesized and studied intensively 5–16. The studies indicate an estimated ZT = 0.7 for Ba 8 Ga 16 Ge 30 at 700 K and 0.87 for Ba 8 Ga 16 Si 30 at 870 K 7, 16.…”

Section: Introductionmentioning

confidence: 99%

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

Li¹,

Li²,

Deng³

et al. 2012

Physica Status Solidi (b)

View full text Add to dashboard Cite

In the present work we report on the synthesis of type‐I clathrates Sr8Ga16SnxGe30 − x (0 ≤ x ≤ 12). To find out how the substitution of Sn for Ge affects structural stability and electronic structure, the structural and electronic properties for Sr8Ga16SnxGe30 − x (0 ≤ x ≤ 30) have been investigated by a first‐principles method based on the density‐functional theory (DFT). We found that the lattice constants of Sr8Ga16SnxGe30 − x series increase with increasing Sn content, which is consistent with X‐ray diffraction (XRD) results. Calculations indicate that the substitution of Sn for Ge leads to the change of the bulk modulus and the decrease of stability of the structure. It is found that these alloys are all indirect‐gap semiconductors and the bandgap decreases from about 0.36 eV in Sr8Ga16Ge30 to about 0.03 eV in Sr8Ga16Sn30 with increasing Sn content. The decrease of the bandgap is attributed to the increase of the free space for the Sr guest motion, which is accompanied by the guest's low‐energy modes and larger anharmonicity. These mean that an increase in the ratio of Sn‐to‐Ge can not only control the electrical properties of the materials, but also may reduce their thermal conductivity, suggesting that cage‐size tuning is one of the useful means to obtain high‐performance thermoelectric (TE) materials.

show abstract

“…[1][2][3][4] Recently, a large number of investigations have been performed on type-I clathrates with the chemical formula of II 8 III 16 IV 30 , where II= Ba, Sr, and Eu, III= Al, Ga, and In, and IV= Ge, Si, and Sn. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] The unit cell of type-I clathrate consists of two kinds of cages; two dodecahedra and six tetrakaidecahedra formed by group IV and III elements. Alkaline-earth atoms in the cages donate electrons to framework host atoms so that the compound can be considered consisting of positively charged guest ions and negatively charged host cages.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of thermoelectric efficiency in type-VIII clathrate Ba8Ga16Sn30 by Al substitution for Ga

Deng

Saiga

Suekuni

et al. 2010

Journal of Applied Physics

View full text Add to dashboard Cite

Ba 8 Ga 16−x Al x Sn 30 ͑0 Յ x Յ 12͒ were grown from Sn flux to characterize the structural and thermoelectric properties from 300 to 600 K. The lattice parameter increases by 0.5% as x is increased to 10.5 whose value is the solubility limit of Al. The Seebeck coefficients of all samples are largely negative and the absolute values increase to approximately 300 V / K on heating to 600 K. This large thermopower coexists with the metallic behavior in the electrical resistivity. The values of resistivity for 1 Յ x Յ 6 at 300 K are in the range 3.3-3.8 m⍀ cm which is 70% of that for x = 0. As a result, the power factor for x = 4 and 6 has a rather large maximum of 1.83ϫ 10 −3 W / m K 2 at 480 K. The thermal conductivity stays at a low level of 0.72 W/mK up to 480 K, and the sample with x = 6 reaches a ZT value of 1.2 at 500 K.

show abstract

Structure and properties of Ba8Ga16Ge30 clathrates by a novel synthesis method using CO gas reductive atmosphere

Cited by 17 publications

References 8 publications

On the Design of High‐Efficiency Thermoelectric Clathrates through a Systematic Cross‐Substitution of Framework Elements

On the Design of High‐Efficiency Thermoelectric Clathrates through a Systematic Cross‐Substitution of Framework Elements

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

Enhancement of thermoelectric efficiency in type-VIII clathrate Ba8Ga16Sn30 by Al substitution for Ga

Contact Info

Product

Resources

About

Structure and properties of Ba8Ga16Ge30 clathrates by a novel synthesis method using CO gas reductive atmosphere

Cited by 17 publications

References 8 publications

On the Design of High‐Efficiency Thermoelectric Clathrates through a Systematic Cross‐Substitution of Framework Elements

On the Design of High‐Efficiency Thermoelectric Clathrates through a Systematic Cross‐Substitution of Framework Elements

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

Enhancement of thermoelectric efficiency in type-VIII clathrate Ba8Ga16Sn30 by Al substitution for Ga

Contact Info

Product

Resources

About

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