Structure and Raman scattering study on Ba8GaxSi46−x (x=10 and 16) type I clathrates

Nataraj, D.; Nagao, Jiro

doi:10.1016/j.jssc.2004.01.011

Cited by 26 publications

(21 citation statements)

References 20 publications

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“…Other germanium and tin clathrates obeying Zintl criteria are Ba 8 Al 16-x Ge 30+y , which forms vacancies when x ≠ 0 to maintain a Zintl composition [71], and I 8 Te 5.3 Ge 40 [72], Sn 24 P 19.3 I 8-y Cl y [73], and Sn 14 In 10 P 21.2 I 8 [74], all exhibiting spontaneous vacancies. Ba 8 Ga 10 Si 36 is the only silicon-based clathrate thus far reported to exhibit spontaneous vacancy formation, [70,75]. On the other hand, Ba 8 Ga 6 Si 40 , a composition further from the Zintl phase Ba 8 Ga 16 Si 30 , is a bulk superconductor as described above [57], and thus most likely features an unbroken framework.…”

Section: Zintl Concept and Vacanciesmentioning

confidence: 93%

Superconductivity and Magnetism in Silicon and Germanium Clathrates

Ross

2009

Nanoscale Magnetic Materials and Applications

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Clathrates are materials containing closed polyhedral cages stacked to form crystalline frameworks. With Si, Ge, and Sn atoms populating these frameworks, a wide variety of electronic and vibrational properties can be produced in these materials, by substitution upon framework sites or through incorporation of ions in cage-center positions. Commonly-formed structures include the type I, type II, and chiral clathrate types, whose properties will be described here. Ba 8 Si 46 with the type

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Section: Zintl Concept and Vacanciesmentioning

confidence: 93%

Superconductivity and Magnetism in Silicon and Germanium Clathrates

Ross

2009

Nanoscale Magnetic Materials and Applications

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“…Bentien et al reported the Ga site preferences in the host structure [41,42]. Semiconducting behavior due to the vacancies in the framework sites was reported by Nataraj et al [37,38,39]. A maximum ZT value of 0.75 at 1000 K was reached with a high Ga content 17.13 at./f.u.…”

Section: Introductionmentioning

confidence: 92%

“…A series of compounds have been investigated [11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29] and a high value of ZT = 1.35 has been achieved at 900 K for Ba 8 Ga 16 Ge 30 [30], which inspired more enthusiasm to pursue higher ZT in similar clathrates. The iso-structural Ba 8 Ga 16 Si 30 clathrate has also attracted interest and has been studied by several researchers [31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47]. Eisenman et al was first to provide the structure details for this clathrate [31].…”

Section: Introductionmentioning

confidence: 99%

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Structural and Thermoelectric Properties of Cu Substituted Type I Clathrates Ba8CuxSi~32−xGa~14

et al. 2019

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With an attempt to improve the thermoelectric properties of type I clathrates in the Ba-Ga-Si system, we introduce Cu into the framework of the crystal structure. Single crystals are prepared in Ga-flux and characterized by X-ray diffraction techniques and transport measurements for the structural and thermoelectric properties. Our composition analyses show that only a small amount of Cu is determined in the clathrates. The single crystal X-ray diffraction data refinements confirm that Ga atoms prefer the 6c and 24k sites and avoid the 16i sites in the crystal structure. The small amount of Cu affects the crystal structure by compressing the tetrakaidecahedral cage along the direction perpendicular to the six-atom-ring plane. This could be the reason for the high charge carrier concentration, and low electrical resistivity and Seebeck coefficient. We analyze the principal mechanism for our observation and conclude that the Cu substitution can adjust some subtle details of the structure, maintaining the Zintl rule in the type I clathrates.

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“…1 The static and macroscopic properties related to the rattling mode have been studied in many clathrate compounds. [2][3][4][5][6][7][8][9][10][11][12][13] However, very few studies for the microscopic dynamical properties have been reported. 14 To our knowledge, the research of the rattling motion, as the view point of strongly correlated electron system, started after the observation of elastic dispersion by ultrasonic measurements by Goto group, who claimed the origin of the elastic dispersion as rattling motion.…”

Section: Introductionmentioning

confidence: 99%

Guest Ion Motion in Cage Structure Crystals Investigated by Raman Scattering

et al. 2008

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Last five years we have mainly investigated phonons in the following cage compounds by Raman scattering: RT4X12, A8Ga16Ge30, La3Pd20Ge6, RB6, KOs2O6. From this systematic investigation we have clarified the following dynamical properties of the guest ion trapped in the large cages. The vibration of the guest ion is highly anharmonic due to weak atomic interaction between the guest ion and cage atom. This anharmonicity universally decreases the vibration energy of the guest ion with decreasing temperature. The existence of carriers decreases the interaction between the guest atoms and changes the dispersion curve of the guest ion mode to flat, which is the experimental evidence of the weak interaction between the guest atoms. For thermoelectricity, it is found in A8Ga16Ge30 that the off-center rattling decreases lattice thermal conductivity.

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Structure and Raman scattering study on Ba8GaxSi46−x (x=10 and 16) type I clathrates

Cited by 26 publications

References 20 publications

Superconductivity and Magnetism in Silicon and Germanium Clathrates

Superconductivity and Magnetism in Silicon and Germanium Clathrates

Structural and Thermoelectric Properties of Cu Substituted Type I Clathrates Ba8CuxSi~32−xGa~14

Guest Ion Motion in Cage Structure Crystals Investigated by Raman Scattering

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