3 research outputs found
Cu<sub>2</sub>Te Incorporation-Induced High Average Thermoelectric Performance in <i>p</i>‑Type Bi<sub>2</sub>Te<sub>3</sub> Alloys
p-Type (Bi, Sb)2Te3 alloys
are attractive materials for near-room-temperature thermoelectric
applications due to their high atomic masses and large spin–orbit
interactions. However, their narrow band gaps originating from spin–orbit
interactions lead to bipolar excitation, thereby limiting average
thermoelectrics within a local temperature region (300–400
K). Here, we introduce Cu2Te into the Bi0.3Sb1.7Te3 (BST) lattice to implement high thermoelectrics
over a wide temperature range. The carrier concentration is synergistically
modulated via Cu substitution and the evolution of intrinsic point
defects (antisites and vacancies). Furthermore, the chain effect caused
by Cu2Te incorporation in BST is reflected in the improvement
of the weighted mobility μW, thereby enhancing the
power factor in the whole temperature range. Extrinsic and intrinsic
defects due to the incorporation of Cu2Te lead to a significant
reduction in the lattice thermal conductivity κL, which is further demonstrated by Raman spectroscopy.
Combining κL and μW, the quantity factor B increases from 0.5 to 1
with increasing Cu2Te content due to not only the reduction
of κL but also a significant improvement
in electrical properties. Eventually, a peak figure of merit (zT) of ∼1.15 at 423 K is achieved in BST-Cu2Te samples, and an average figure of merit (zTave) of ∼1.12 (350–500 K) surpasses other excellent p-type Bi2Te3-based thermoelectrics.
Such a synergistic effect can facilitate near-room-temperature thermoelectric
applications of Bi2Te3-based alloys and provide
chances for the technology space in thermoelectrics
Promoted Na Solubility and Modified Band Structure for Achieving Exceptional Average <i>ZT</i> by Extra Mn Doping in PbTe
Na doping strategy provides an effective avenue to upgrade
the
thermoelectric performance of PbTe-based materials by optimizing electrical
properties. However, the limited solubility of Na inherently restricts
the efficiency of doping, resulting in a relatively low average ZT, which poses challenges for the development and application
of subsequent devices. Herein, to address this issue, the introduced
spontaneous Pb vacancies and additional Mn doping synergistically
promote Na solubility with a further modified valence band structure.
Furthermore, the induced massive point defects and multiscale microstructure
greatly strengthen the scattering of phonons over a wide frequency
range, leading to a remarkable ultralow lattice thermal conductivity
of ∼0.42 W m–1 K–1. As
a result, benefiting from the significantly enhanced Seebeck coefficient
and superior thermal transports, a high peak ZT of
∼2.1 at 773 K and an excellent average ZT of
∼1.4 between 303 and 823 K are simultaneously achieved in Pb0.93Na0.04Mn0.02Te. This work proposes
a simple and constructive method to obtain high-performance PbTe-based
materials and is promising for the development of thermoelectric power
generation devices
Ga-Doping-Induced Carrier Tuning and Multiphase Engineering in n‑type PbTe with Enhanced Thermoelectric Performance
P-type
lead telluride (PbTe) emerged as a promising thermoelectric material
for intermediate-temperature waste-heat-energy harvesting. However,
n-type PbTe still confronted with a considerable challenge owing to
its relatively low figure of merit <i>ZT</i> and conversion
efficiency η, limiting widespread thermoelectric applications.
Here, we report that Ga-doping in n-type PbTe can optimize carrier
concentration and thus improve the power factor. Moreover, further
experimental and theoretical evidence reveals that Ga-doping-induced
multiphase structures with nano- to micrometer size can simultaneously
modulate phonon transport, leading to dramatic reduction of lattice
thermal conductivity. As a consequence, a tremendous enhancement of <i>ZT</i> value at 823 K reaches ∼1.3 for n-type Pb<sub>0.97</sub>Ga<sub>0.03</sub>Te. In particular, in a wide temperature
range from 323 to 823 K, the average <i>ZT</i><sub>ave</sub> value of ∼0.9 and the calculated conversion efficiency η
of ∼13% are achieved by Ga doping. The present findings demonstrate
the great potential in Ga-doped PbTe thermoelectric materials through
a synergetic carrier tuning and multiphase engineering strategy