Cs8−xSi46: A Type‐I Clathrate with Expanded Silicon Framework

Wosylus, Aron; Veremchuk, Igor; Schnelle, Walter; Baitinger, Michael; Schwarz, Ulrich; Grin, Yuri

doi:10.1002/chem.200900307

Cited by 39 publications

(32 citation statements)

References 25 publications

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“…On the other hand, number of the encapsulated Cs in Si 46 cage was 7.6, 32) which is larger than that of Rb. This difference should be originated in the synthesized condition, where Cs 7.6 Si 46 was synthesized under high temperature and pressure.…”

Section: Resultsmentioning

confidence: 80%

Energetic Stability and Thermoelectric Property of Alkali-Metal-Encapsulated Type-I Silicon-Clathrate from First-Principles Calculation

2013

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Possible combinations of alkali metal guest atoms and substitutional group-13 atoms in type-I Si clathrate and their thermoelectric properties were investigated using first-principles calculations. All alkali metals could be encapsulated as the guest element into a Si 46 cage, and either Al or Ga was suitable for a substitutional atom. From the formation energy, possible clathrate compositions were selected as K 8 38 . The thermoelectric properties of these compositions were calculated as functions of temperature and carrier density, using the Boltzmann transport equation and the calculated band energy. The obtained dependences of the Seebeck coefficient and electrical conductivity on the carrier density were discussed from the viewpoint of band structure. The thermoelectric properties were optimized to maximize ZT for each composition by controlling the carrier density. ZT µ 0.75 was predicted as the highest ZT value for hole-doped Cs 8 Ga 8 Si 38 .

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Section: Resultsmentioning

confidence: 80%

Energetic Stability and Thermoelectric Property of Alkali-Metal-Encapsulated Type-I Silicon-Clathrate from First-Principles Calculation

2013

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“…A relatively low thermal conductivity and a high electrical conductivity of some intermetallic clathrates [2] identify them as promising materials for thermoelectric applications. For example, a maximum value of the dimensionless figure of merit ZT = 1.35 was reached for Ba 8 Ga 16 Ge 30 at 900 K, [3] although other values have also been reported. [4] For n-doped Ba 8 Ga 16 Sn 30 , the highest value of the figure of merit (1.45) is reported at 500 K. [5] In the meantime, many new representatives of Group 14 intermetallic clathrates of known types have been found [6] and completely new types of clathrates have recently been suggested.…”

Section: Introductionmentioning

confidence: 99%

A Combined Metal–Halide/Metal Flux Synthetic Route towards Type‐I Clathrates: Crystal Structures and Thermoelectric Properties of A₈Al₈Si₃₈ (A=K, Rb, and Cs)

Baran

Senyshyn

Karttunen

et al. 2014

Chemistry A European J

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Single‐phase samples of the compounds K8Al8Si38 (1), Rb8Al8Si38 (2), and Cs7.9Al7.9Si38.1 (3) were obtained with high crystallinity and in good quantities by using a novel flux method with two different flux materials, such as Al and the respective alkali‐metal halide salt (KBr, RbCl, and CsCl). This approach facilitates the removal of the product mixture from the container and also allows convenient extraction of the flux media due to the good solubility of the halide salts in water. The products were analyzed by means of single‐crystal X‐ray structure determination, powder X‐ray and neutron diffraction experiments, 27Al‐MAS NMR spectroscopy measurements, quantum chemical calculations, as well as magnetic and transport measurements (thermal conductivity, electrical resistivity, and Seebeck coefficient). Due to the excellent quality of the neutron diffraction data, the difference between the nuclear scattering factors of silicon and aluminum atoms was sufficient to refine their mixed occupancy at specific sites. The role of variable‐range hopping for the interpretation of the resistivity and the Seebeck coefficient is discussed.

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“…For compounds K 7.62(1) Si 46 and Rb 6.15(2) Si 46 , when guest atom vacancy is present, occupancy at 6 d site is preferred and 2 a site has lower s.o.f , 88.5(4)% at K 7.62(1) Si 46 2 a site and 21.8(5)% at Rb 6.15(2) Si 46 2 a site [4]. Similarly, in sample Cs 7.8(1) Si 46 , s.o.f of 2 a site is 0.881(4) while 6 d site is close to fully occupied [5]. …”

Section: Structurementioning

confidence: 99%

“…The eight guest atoms in the unit cell are located at the Wyckoff positions 2 a and 6 d , which centers the two types of polyhedra found in type I clathrate: 20-vertex pentagonal dodecahedra and 24-vertex tetrakaidecahedra. Following the discovery of Na 8-x Si 46 , the alkali metals series (A = K, Rb, Cs) of type I clathrate were synthesized from the elements by annealing, with the Cs clathrate being a high pressure phase [4,5]. The alkali metals´ guest atoms in the silicon-containing clathrate phases donate electrons, and these phases are metallic [1].…”

Section: Introductionmentioning

confidence: 99%

Earth Abundant Element Type I Clathrate Phases

2016

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Earth abundant element clathrate phases are of interest for a number of applications ranging from photovoltaics to thermoelectrics. Silicon-containing type I clathrate is a framework structure with the stoichiometry A8-xSi46 (A = guest atom such as alkali metal) that can be tuned by alloying and doping with other elements. The type I clathrate framework can be described as being composed of two types of polyhedral cages made up of tetrahedrally coordinated Si: pentagonal dodecahedra with 20 atoms and tetrakaidecahedra with 24 atoms in the ratio of 2:6. The cation sites, A, are found in the center of each polyhedral cage. This review focuses on the newest discoveries in the group 13-silicon type I clathrate family: A8E8Si38 (A = alkali metal; E = Al, Ga) and their properties. Possible approaches to new phases based on earth abundant elements and their potential applications will be discussed.

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Cs_8−xSi₄₆: A Type‐I Clathrate with Expanded Silicon Framework

Cited by 39 publications

References 25 publications

Energetic Stability and Thermoelectric Property of Alkali-Metal-Encapsulated Type-I Silicon-Clathrate from First-Principles Calculation

Energetic Stability and Thermoelectric Property of Alkali-Metal-Encapsulated Type-I Silicon-Clathrate from First-Principles Calculation

A Combined Metal–Halide/Metal Flux Synthetic Route towards Type‐I Clathrates: Crystal Structures and Thermoelectric Properties of A₈Al₈Si₃₈ (A=K, Rb, and Cs)

Earth Abundant Element Type I Clathrate Phases

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Cs8−xSi46: A Type‐I Clathrate with Expanded Silicon Framework

Cited by 39 publications

References 25 publications

Energetic Stability and Thermoelectric Property of Alkali-Metal-Encapsulated Type-I Silicon-Clathrate from First-Principles Calculation

Energetic Stability and Thermoelectric Property of Alkali-Metal-Encapsulated Type-I Silicon-Clathrate from First-Principles Calculation

A Combined Metal–Halide/Metal Flux Synthetic Route towards Type‐I Clathrates: Crystal Structures and Thermoelectric Properties of A8Al8Si38 (A=K, Rb, and Cs)

Earth Abundant Element Type I Clathrate Phases

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Cs_8−xSi₄₆: A Type‐I Clathrate with Expanded Silicon Framework

A Combined Metal–Halide/Metal Flux Synthetic Route towards Type‐I Clathrates: Crystal Structures and Thermoelectric Properties of A₈Al₈Si₃₈ (A=K, Rb, and Cs)