Abstract:
Using a set of controlled in situ grown lamellar
composites of (Cu2Te)62.02−(Sb2Te3)37.98, we report a remarkable
variation of transport properties of thermoelectricity not only as a
function of microstructural length scale but also as a function of
direction-dependent arrangement of the phases and hence their
interfaces. A quantitative evaluation of the microstructure along
the transverse and the longitudinal directions of growth, imposed
by the temperature gradient and growth rate in a unidirectional
solidification setup, has been carried out. The microstructure is
quantified through image analysis using fast Fourier transforms as
well as a cluster base connectivity model and is further correlated
with the thermoelectric transport properties. A marked anisotropy
of properties as a function of measurement direction in the
microstructural landscape could be observed. A maximum power factor of ∼1.4 mW m−1 K−2 and a figure of merit of 0.29 could be
obtained at 580 K along the transverse direction for the sample with the characteristic microstructural length scale of 2.41 μm. This
has an implication in engineering a thermoelectric device in terms of engineering power factor and output power density. For a ΔT
of 250 K, we report a difference of 0.4 W cm−2 in output power density between the transverse and the longitudinal directions that
have an identical microstructural length scale of 2.41 μm
