Synthesis and Structural Characterization of Single-Crystal K7.5Si46 and K17.8Si136 Clathrates

Stefanoski, Stevce; Nolas, George S.

doi:10.1021/cg200756r

Cited by 38 publications

(33 citation statements)

References 51 publications

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“…The lattice parameter for Rb 11.5 Si 136 , as expected, has an intermediate value between that reported for K 17.2 Si 136 [19] and Cs 8 Si 136 [6]. In all cases the silicon framework sites were found to be fully occupied (no vacancies), in agreement with prior results for binary silicon clathrates [7,16,18,19,26,27,28].…”

Section: Resultssupporting

confidence: 87%

“…The lattice parameters for K 7.6 Si 46 , Rb 6.2 Si 46 , and Cs 7.8 Si 136 show good agreement with those synthesized by other preparation methods [7,16,18,19,24,25,26]. The lattice parameter for Rb 11.5 Si 136 , as expected, has an intermediate value between that reported for K 17.2 Si 136 [19] and Cs 8 Si 136 [6].…”

Section: Resultssupporting

confidence: 76%

“…In a rigid-band model, a high concentration of conduction electrons are provided by charge transfer from the alkali-metal guests, thus inducing metallic behavior, as confirmed experimentally [15,29]. In contrast to SPS-prepared Na 8 Si 46 and Na 24 Si 136 , which show full occupancy of the polyhedral cages by sodium [19], the SPS-prepared clathrates of potassium, rubidium and caesium exhibit partial occupancy of the alkali-atom positions (the specific refined compositions are given in Table 2 and Table 3). …”

Section: Resultsmentioning

confidence: 91%

“…Single-crystals suitable for measurement of intrinsic transport properties were first prepared by the electrochemically-driven transformation of Na 4 Si 4 to Na 24 Si 136 during the spark plasma treatment (SPS) [16,17]. Another approach—the kinetically controlled thermal decomposition (KCTD) method—can also provide relatively large single crystals [18,19]. Recently, a thermal decomposition at lower temperatures was employed for the preparation of Na 24- x (Si y Ge 1- y ) 136 and proved to be useful for the synthesis of silicon clathrates [20].…”

Section: Introductionmentioning

confidence: 99%

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Binary Alkali-Metal Silicon Clathrates by Spark Plasma Sintering: Preparation and Characterization

Veremchuk¹,

Beekman

Antonyshyn³

et al. 2016

Materials

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Abstract:The binary intermetallic clathrates K 8-x Si 46 (x = 0.4; 1.2), Rb 6.2 Si 46 , Rb 11.5 Si 136 and Cs 7.8 Si 136 were prepared from M 4 Si 4 (M = K, Rb, Cs) precursors by spark-plasma route (SPS) and structurally characterized by Rietveld refinement of PXRD data. The clathrate-II phase Rb 11.5 Si 136 was synthesized for the first time. Partial crystallographic site occupancy of the alkali metals, particularly for the smaller Si 20 dodecahedra, was found in all compounds. SPS preparation of Na 24 Si 136 with different SPS current polarities and tooling were performed in order to investigate the role of the electric field on clathrate formation. The electrical and thermal transport properties of K 7.6 Si 46 and K 6.8 Si 46 in the temperature range 4-700 K were investigated. Our findings demonstrate that SPS is a novel tool for the synthesis of intermetallic clathrate phases that are not easily accessible by conventional synthesis techniques.

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Section: Resultssupporting

confidence: 87%

Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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Binary Alkali-Metal Silicon Clathrates by Spark Plasma Sintering: Preparation and Characterization

Veremchuk¹,

Beekman

Antonyshyn³

et al. 2016

Materials

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“…The advantage of the SPS technique is the synthesis of single crystal. 42,43,45 Ionic liquid (IL) synthesis Redox reaction of Zintl precursors in the presence of an IL can be carried out at low temperatures ( ≤ 300 • C) to synthesize type I and type II clathrates. The first successful synthesis of a guest free type II Ge clathrate was accomplished via the reaction of IL (e.g, n-dodecyltrimethylammonium chloride and AlCl 3 ) and Zintl precursor (Na 4 Ge 9 ).…”

Section: Direct Synthesis From Elementsmentioning

confidence: 99%

Group IV clathrates: synthesis, optoelectonic properties, and photovoltaic applications

et al. 2014

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Group IV clathrates are a unique class of guest/framework type compounds that are considered potential candidates for a wide range of applications (superconductors to semiconductors). To date, most of the research on group IV clathrates has focused heavily on thermoelectric applications. Recently, these materials have attracted attention as a result of their direct, wide band gaps for possible use in photovoltaic applications. Additionally, framework alloying has been shown to result in tunable band gaps. In this review, we discuss the current work and future opportunities concerning the synthesis and optical characterization of group IV clathrates for optoelectronics applications.

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Silicon Clathrate‐Supported Catalysts with Low Work Functions for Ammonia Synthesis

Al Maksoud,

Bacha,

Pixius

et al. 2024

Advanced Materials

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Diamond‐type silicon has a work function of ≈4.8 eV, and conventional n‐ or p‐type doping modifies the value only between 4.6 and 5.05 eV. Here, it is shown that the alkali clathrates AxSi46 have substantially lower work functions approaching 2.6 eV, with clear trends between alkali electropositivity and clathrate cage size. The low work function enables alkali clathrates such as K8Si46 to be effective Haber‐Bosch catalyst supports for NH3 synthesis. The catalytic properties of Si, Ge, and Sn‐based clathrates are investigated while supporting Fe and Ru on the surface. The activity largely scales with the work function, and low activation energies below 60 kJ mol−1 are observed due to strong electron donation effects from the support. Ru metal and Sn clathrates seem to be unsuitable for stability issues. Compared to other similar hydride/electride catalysts, the simple structure and composition combined with stability in air/water make a systematic study of these clathrates possible and open the door to other electron‐rich Zintl phases and related intermetallics as low‐work function materials suitable for catalysis. The observed low work function may also have implications for other existing electronic applications.

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Synthesis and Structural Characterization of Single-Crystal K_7.5Si₄₆ and K_17.8Si₁₃₆ Clathrates

Cited by 38 publications

References 51 publications

Binary Alkali-Metal Silicon Clathrates by Spark Plasma Sintering: Preparation and Characterization

Binary Alkali-Metal Silicon Clathrates by Spark Plasma Sintering: Preparation and Characterization

Group IV clathrates: synthesis, optoelectonic properties, and photovoltaic applications

Silicon Clathrate‐Supported Catalysts with Low Work Functions for Ammonia Synthesis

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