Microstructure and thermoelectric properties of Si-WSi2 nanocomposites. (15th February 2017)

• Record Type: Journal Article
• Authors: Stoetzel, Julia; Schneider, Tom; Mueller, Mathis M.; Kleebe, Hans-Joachim; Wiggers, Hartmut; Schierning, Gabi; Schmechel, Roland
• Is Part Of: Acta materialia. Volume 125(2017)
• Page Start: 321
• Page End: 326
• Publication Date: 2017-02-15
• Subjects: Nanocomposites -- Thermoelectric material -- Self-assembly -- Transport properties -- Nanocrystalline silicon; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2016.11.069
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Nanocomposites of n-doped Si/WSi2 were prepared and morphologically and thermoelectrically investigated. The composites were densified by spark-plasma-sintering of doped Si nanoparticles with WSi2 nanoinclusions. The nanoparticles were synthesized in a gas-phase process. The microstructure of the bulk nanocomposite shows an inhomogeneous distribution of the WSi2 nanoinclusions in form of WSi2 -rich and -depleted regions. This inhomogeneity is not present in the starting material and is assigned to a self-organizing process during sintering. The inhomogeneities are in the micrometer range and may act as scattering centers for long-wavelength phonons. The WSi2 nanoinclusions grow during sintering from originally 3–7 nm up to 30–143 nm depending on the total W content and might act as scattering centers for the medium wavelength range of phonons. Further, the growth of Si grains is suppressed by the WSi2 inclusions, which leads to an enhanced grain boundary density. Adding 1 at% W reduces lattice thermal conductivity by almost 35% within the temperature range from 300 K to 1250 K compared to pure, nanocrystalline silicon (doped). By addition of 6 at% W a reduction of 54% in lattice thermal conductivity is achieved. Although little amounts of W slightly reduce the power factor an enhancement of the thermoelectric figure of merit of 50% at 1250 K compared to a tungsten-free reference was realized. Graphical abstract: Image 1