Die verbindungen AII8BIII16BIV30 (AII ≡ Sr, Ba; BIII≡ Al, Ga; BIV ≡ Si, Ge, Sn) und ihre käfigstrukturen

Eisenmann, Β.; Schäfer, Herbert; Zagler, R.

doi:10.1016/0022-5088(86)90609-0

Cited by 240 publications

(156 citation statements)

References 5 publications

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“…The XRD patterns of the samples agreed well with the previously reported Ba 8 Ga 16 Ge 30 structure, 21,23,24 but for several syntheses substantial amounts of impurity phases of mainly GaSb and a diffuse Zn phase were present. For this reason only samples S1, Z1, and Z2, which showed no presence of any impurity phase in their XRD diffractograms, were analyzed further together with the unsubstituted sample G1 for thermoelectric evaluation.…”

Section: A Sample Preparation and Characterizationsupporting

confidence: 88%

Thermoelectric properties of partly Sb- and Zn-substituted Ba8Ga16Ge30 clathrates

Cederkrantz

Nygren

Palmqvist

2010

Journal of Applied Physics

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The effects on the thermoelectric properties of n-Ba8Ga16Ge30 when substituting small amounts of the Ga or Ge with Sb or Zn have been investigated. A number of syntheses were prepared in quaternary systems of Ba8Ga16Ge30 substituted with either Sb or Zn but only three samples were found to yield single phase products with nominal compositions of Ba8Ga15Sb1Ge30, Ba8Ga15Zn1Ge30 and Ba8Ga16Ge28Zn2, respectively. When Ge was substituted for Zn the resulting sample remained n-type and an increase in thermopower and a decrease in thermal conductivity were achieved. These positive effects were accompanied with an increased electrical resistivity and thus the ZT was only somewhat improved up to about 400 °C. When substituting Ga with either Sb or Zn samples remained n-type but showed decreased thermopower and increased electrical resistivity and thermal conductivity. It is thus concluded that substitution of Ga with Zn or Sb is detrimental for the thermoelectric properties of Ba8Ga16Ge30, whereas substitution of Ge with Zn appears a potent method for improving its performance.

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Section: A Sample Preparation and Characterizationsupporting

confidence: 88%

Thermoelectric properties of partly Sb- and Zn-substituted Ba8Ga16Ge30 clathrates

Cederkrantz

Nygren

Palmqvist

2010

Journal of Applied Physics

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“…We considered 33 distinct superstructures having different atomic arrangements, starting with atomic positions of the reported parent Ba 8 Ge 30 Al 16 structure. 28 Where justified by initial results we also used WIEN2k to minimize internal structural parameters before finalizing the results.…”

Section: Computational Methods and Discussionmentioning

confidence: 99%

NMR experiments and electronic structure calculations in type-I BaAlGe clathrates

Gou

Rodriguez

et al. 2009

Phys. Rev. B

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We describe 27 Al NMR experiments on Ba 8 Al x Ge 46−x type-I clathrates coupled with ab initio computational studies. For x = 16, calculated spectra determined by the ab initio results gave good agreement with the measurements, with best-fitting configurations also corresponding to the computed lowest-energy atomic arrangements. Analysis of the NMR results showed that a distribution of Knight shifts dominates the central portion of the line. Computational results demonstrate that this stems from the large variation of carrier density on different sites. Al-deficient samples with x = 12 and 13 exhibited a split central NMR peak, signaling two main local environments for Al ions, which we connected to the presence of vacancies. Modeling of the wide-line spectrum for x = 12 indicates a configuration with more Al on the 24k site than for x = 16. The results indicate the importance of nonbonding hybrids adjacent to the vacancies in the electronic structure near E F . We also address the static distortions from Pm3n symmetry in these structures.

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“…In a large fraction thereof, chemical bonding can be described in accordance with the Zintl-Klemm concept. In phases of electropositive metals with germanium like K 8 Ge 44 & 2 or A 8 M 16 Ge 30 (A ¼ Sr, Ba; M ¼ Al, Ga), group 14 elements form polyanions in electron-precise compounds by the formation of electron pairs around defects [1,2] or by substitution of group 14 elements with group 13 atoms [3,4]. In phases MGe 6Àx Ga y , (M ¼ Eu, Sr) the electronprecise composition with x ¼ y ¼ 2 can be synthesized for M ¼ Eu [5] and the corresponding binary strontium germanide with M ¼ Sr, xE0.5 and y ¼ 0 (SrGe 6Àx ) comprises vacancies [6], which indicates that it can fulfill the 8ÀN rule.…”

Section: Introductionmentioning

confidence: 99%

High-pressure synthesis of the electron-excess compound CaSi₆

Wosylus

Prots

Burkhardt

et al. 2007

Science and Technology of Advanced Materials

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The binary phase CaSi 6 is prepared at a pressure of 10(1) GPa and a temperature of 1520(150) K. X-ray single-crystal structure refinements and powder diffraction data of quenched samples reveal that the compound crystallizes in the orthorhombic crystal system (space group Cmcm, a ¼ 4.4953(5) Å , b ¼ 10.078(1) Å , c ¼ 11.469(1) Å ). At ambient pressure, exothermic decomposition into CaSi 2 and Si at 737(5) K indicates that the compound is a metastable high-pressure phase. Physical property measurements reveal that the new hexasilicide is diamagnetic and a bad metallic conductor, with resistivity rE900 mO cm at 300 K. r

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Die verbindungen AII8BIII16BIV30 (AII ≡ Sr, Ba; BIII≡ Al, Ga; BIV ≡ Si, Ge, Sn) und ihre käfigstrukturen

Cited by 240 publications

References 5 publications

Thermoelectric properties of partly Sb- and Zn-substituted Ba8Ga16Ge30 clathrates

Thermoelectric properties of partly Sb- and Zn-substituted Ba8Ga16Ge30 clathrates

NMR experiments and electronic structure calculations in type-I BaAlGe clathrates

High-pressure synthesis of the electron-excess compound CaSi₆

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Die verbindungen AII8BIII16BIV30 (AII ≡ Sr, Ba; BIII≡ Al, Ga; BIV ≡ Si, Ge, Sn) und ihre käfigstrukturen

Cited by 240 publications

References 5 publications

Thermoelectric properties of partly Sb- and Zn-substituted Ba8Ga16Ge30 clathrates

Thermoelectric properties of partly Sb- and Zn-substituted Ba8Ga16Ge30 clathrates

NMR experiments and electronic structure calculations in type-I BaAlGe clathrates

High-pressure synthesis of the electron-excess compound CaSi6

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Product

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High-pressure synthesis of the electron-excess compound CaSi₆