Journal ArticleDOI
Synthesis and characterization of Mg2Si/Si nanocomposites prepared from MgH2 and silicon, and their thermoelectric properties
Tanghong Yi,Shaoping Chen,Shawn Li,Hao Yang,Sabah K. Bux,Zhixi Bian,Nebil A. Katcho,Ali Shakouri,Natalio Mingo,Jean-Pierre Fleurial,Nigel D. Browning,Susan M. Kauzlarich +11 more
TLDR
In this article, Si nanoparticles embedded in a Mg2Si matrix were successfully synthesized at 623 K from MgH2 and Bi containing Si nanoparticle powders.Abstract:
Silicon (Si) nanoparticles embedded in a Mg2Si matrix (Mg2Si/xSi) have been successfully synthesized at 623 K from MgH2 and Bi containing Si nanoparticle powders. The use of MgH2 in this synthetic route avoids the formation of oxides through the generation of hydrogen and provides a route to homogeneously mixed Si nanoparticles within a doped Mg2Si matrix. The samples were characterized by powder X-ray diffraction, thermogravimetry/differential scanning calorimetry (TG/DSC), electron microprobe analysis (EMPA), and scanning transmission electron microscopy (STEM). The final crystallite size of Mg2Si obtained from the XRD patterns is about 50 nm for all the samples and the crystallite size of Si inclusions is approximately 17 nm. Theoretical calculations indicate that ∼5 mol% concentrations of Si nanoparticles with diameters in the 5–50 nm range could decrease the lattice thermal conductivity of Mg2Si by about 1–10% below the matrix value. Reduction in thermal conductivity was observed with the smallest amount of Si, 2.5 mol%. Larger amounts, x = 10 mol%, did not provide any further reduction in thermal conductivity. Analysis of the microstructure of the Bi doped Mg2Si/xSi nanocomposites showed that the Bi dopant has a higher concentration at grain boundaries than within the grains and Bi preferentially substitutes the Mg site at the boundaries. The nanocomposite carrier concentration and mobility depend on the amount of Bi and Si inclusions in a complex fashion. Agglomerations of Si start to show up clearly in the Bi doped 5 mol% nanocomposite. While the inclusions result in a lower thermal conductivity, electrical resistivity and Seebeck are negatively affected as the presence of Si inclusions influences the amount of Bi dopant and therefore the carrier concentration. The x = 2.5 mol% nanocomposite shows a consistently higher zT throughout the measured temperature range until the highest temperatures where a dimensionless figure of merit zT ∼ 0.7 was obtained at 775 K for Mg2Si/xSi with x = 0 and 2.5 mol%. With optimization of the electronic states of the matrix and nanoparticle, further enhancement of the figure of merit may be achieved.read more
Citations
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Journal ArticleDOI
A practical field guide to thermoelectrics: Fundamentals, synthesis, and characterization
Alex Zevalkink,David M. Smiadak,Jeffrey L. Blackburn,Andrew J. Ferguson,Michael L. Chabinyc,Olivier Delaire,Olivier Delaire,Jian Wang,Jian Wang,Kirill Kovnir,Kirill Kovnir,Joshua Martin,Laura T. Schelhas,Taylor D. Sparks,Stephen Dongmin Kang,Maxwell Dylla,G. Jeffrey Snyder,Brenden R. Ortiz,Eric S. Toberer +18 more
TL;DR: In this article, the authors present a review of the state-of-the-art in the field of thermoelectric materials with a focus on bulk inorganic materials, including powder and single crystal synthesis, error analysis, and modeling of transport data using an effective mass model.
Journal ArticleDOI
Microstructural effects on thermoelectric efficiency: A case study on magnesium silicide
Johannes de Boor,Titas Dasgupta,Hendrik Kolb,Camille Compere,Klemens Kelm,Echard Mueller,Echard Mueller +6 more
TL;DR: In this article, the authors investigated the microstructural effects on thermoelectric transport in Mg2Si and found that small amounts of impurity phases can heavily impair electrical transport.
Journal ArticleDOI
Morphology and size control of octahedral and cubic primary Mg2Si in an Mg–Si system by regulating Sr contents
TL;DR: In this article, an effective, one-step and cheap method to control the morphologies and sizes of primary Mg2Si crystals in metallic melts, which is critical to achieve industrial application of light alloys with high strength and toughness.
Journal ArticleDOI
Intercalation Compounds from LiH and Graphite: Relative Stability of Metastable Stages and Thermodynamic Stability of Dilute Stage Id
TL;DR: In this paper, the formation and thermal stability of metastable staged Li-graphite intercalation compounds (Li-GICs) close to the competing formation of the thermodynamically stable carbide Li2C2.
Journal ArticleDOI
Synthesis, Structure, Thermoelectric Properties, and Band Gaps of Alkali Metal Containing Type I Clathrates: A8Ga8Si38 (A = K, Rb, Cs) and K8Al8Si38
TL;DR: In this paper, a series of alkali metal containing compounds with type I clathrate structure, A8Ga8Si38 (A = K, Rb, Cs) and K8Al 8Si38, were synthesized and characterized.
References
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