Abstract
Bi2Te3 and CoSb3 based nanomaterials were synthesized and their
thermoelectric, structural, and vibrational properties analyzed to
assess and reduce ZT-limiting mechanisms. The same preparation
and/or characterization methods were applied in the different
materials systems. Single-crystalline, ternary p-type Bi15Sb29Te56,
and n-type Bi38Te55Se7 nanowires with power factors comparable
to nanostructured bulkmaterialswere prepared by potential-pulsed
electrochemical deposition in a nanostructured Al2O3 matrix.
p-type Sb2Te3, n-type Bi2Te3, and n-type CoSb3 thin films were
grown at room temperature using molecular beam epitaxy and
were subsequently annealed at elevated temperatures. This yielded
polycrystalline, single phase thin films with optimized charge
carrier densities. In CoSb3 thin films the speed of sound could
be reduced by filling the cage structure with Yb and alloying
with Fe yielded p-type material. Bi2(Te0.91Se0.09)3/SiC and
(Bi0.26Sb0.74)2Te3/SiC nanocomposites with low thermal conductivities
and ZT values larger than 1 were prepared by spark
plasma sintering. Nanostructure, texture, chemical composition, as
well as electronic and phononic excitations were investigated by
X-ray diffraction, nuclear resonance scattering, inelastic neutron
scattering, M€ossbauer spectroscopy, and transmission electron
microscopy. For Bi2Te3 materials, ab-initio calculations together
with equilibrium and non-equilibrium molecular dynamics
simulations for point defects yielded their formation energies
and their effect on lattice thermal conductivity, respectively.
Current advances in thermoelectric Bi2Te3 and CoSb3 based
nanomaterials are summarized. Advanced synthesis and characterization
methods and theoreticalmodelingwere combined to
assess and reduce ZT-limiting mechanisms in these materials.
