Among the various functional materials, thermoelectric
materials, which convert temperature gradient into electrical
current, or reverse, have attracted much attention
due to their ability to generate power from waste
heat.1–7 Nanostructuring in thermoelectric materials is
expected to enhance thermoelectric properties by reducing
the thermal conductivity and improving the power
factor of the homogeneous bulk materials.8–11 Theoretical
predictions1213 and experimental observations14 15 of
enhanced properties in nanostructured materials have motivated
interest in employing microstructure in bulk thermoelectric
materials to improve properties owing to both
a higher electronic density of states near the Fermi level
and an increased phonon scattering. PbTe and PbTe-based
solid solutions are promising thermoelectric materials in
the intermediate range of temperature (500–900 K),2 15 16
and the results demonstrate that a large Seebeck coefficient
of 679.8 V/K can be obtained from the nanorods at
room temperature, about 2.56 times larger than that of the
PbTe bulk material.17 18 Terasaki et al. have reported the
large thermopower in the layered compound NaCo2O4,19
in which the thermopower of this oxide increases with
increase in temperature, and reaches 100 mV/K at 300 K.
The importance of thermoelectric response in transition
metal oxides has been recognized in the development
of new thermoelectric materials, as the stability of
oxide is much higher than that of chalcogenides.