<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 WSi₂inclusions, 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.
<全文連結>