Lead telluride is one of the most attractive state-of-the-art thermoelectric (TE) materials. Therefore, any improvement of its average thermoelectric figure of merit (ZT)av over a broad temperature range is a...
In this work, we show the simultaneous enhancement of electrical transport and reduction of phonon propagation in p-type PbTe codoped with Tl and Na. The effective use of advanced electronic structure engineering improves the thermoelectric power factor S 2 σ over the temperature range from 300 to 825 K. A rise in the Seebeck coefficient S was obtained due to the enhanced effective mass m*, coming from the Tl resonance state in PbTe. Due to the presence of additional carriers brought by Na codoping, electrical conductivity became significantly improved. Furthermore, Tl and Na impurities induced crystal lattice softening, remarkably reducing lattice thermal conductivity, which was confirmed by a measured low speed of sound v m and high internal strain Cε XRD . Eventually, the combination of both the attuned electronic structure and the lattice softening effects led to a very high ZT value of up to ∼2.1 for the Pb 1−x−y Tl x Na y Te samples. The estimated energy conversion efficiency shows the extraordinary value of 15.4% (T c = 300 K, T h = 825 K), due to the significantly improved average thermoelectric figure of merit ZT ave = 1.05. This work demonstrates that the combination of impurity resonance scattering and crystal lattice softening can be a breakthrough concept for advancing thermoelectrics.
Bi2Te3-based alloys are the main
materials
for the construction of low- and medium-temperature thermoelectric
modules. In this work, the microstructure and thermoelectric properties
of Cl-doped Bi2Te3–x
Se
x
alloys were systematically investigated
considering the high anisotropy inherent in these materials. The prepared
samples have a highly oriented microstructure morphology, which results
in very different thermal transport properties in two pressing directions.
To accurately separate the lattice, electronic, and bipolar components
of the thermal conductivity over the entire temperature range, we
employed a two-band Kane model to the Cl-doped Bi2Te3–x
Se
x
alloys.
It was established that Cl atoms act as electron donors, which tune
the carrier concentration and effectively suppress the minority carrier
transport in Bi2Te3–x
Se
x
alloys. The estimated value of the
lattice thermal conductivity was found to be as low as 0.15 Wm–1 K–1 for Bi2Te3–x–y
Se
x
Cl
y
with x = 0.6
and y = 0.015 at 673 K in parallel to the pressing
direction, which is among the lowest values reported for crystalline
materials. The large reduction of the lattice thermal conductivity
in both pressing directions for the investigated Bi2Te3–x
Se
x
alloys
is connected with the different polarities of the Bi-(Te/Se)1 and
Bi-(Te/Se)2 bonds, while the lone-pair (Te/Se) interactions are mainly
responsible for the extremely low lattice thermal conductivity in
the parallel direction. As a result of the enhanced power factor,
suppressed bipolar conduction, and ultralow lattice thermal conductivity,
a maximum ZT of 1.0 at 473 K has been received in the Bi2Te2.385Se0.6Cl0.015 sample.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.