Dense dislocations enable high-performance PbSe thermoelectric at low-medium temperatures.

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Lead selenide (PbSe)-based materials show potential for medium-temperature thermoelectric applications.
• Near-room-temperature thermoelectric properties of PbSe are underexplored, limiting average ZT (ZT_ave) at lower temperatures.
• Enhancing low-temperature thermoelectric performance is crucial for broader applications.

Purpose of the Study:

• To investigate and improve the thermoelectric properties of PbSe-based materials near room temperature.
• To achieve a high average figure of merit (ZT_ave) at low and low-medium temperatures.
• To understand the underlying mechanisms responsible for enhanced thermoelectric performance.

Main Methods:

• Synthesis of n-type PbSe-based material (Pb_1.02Se_0.72Te_0.20S_0.08-0.3%Cu) through heavy Te/S alloying and Cu interstitial doping.
• Evaluation of dislocation density using the modified Williamson-Hall method.
• Microstructure observation to identify dislocation types (screw and edge) and their characteristics.

Main Results:

• Achieved a high ZT_ave of 0.90 at low temperatures (300-573 K) and 0.96 at low-medium temperatures (300-773 K).
• Observed ultralow lattice thermal conductivity attributed to dense dislocations (up to 5.4 × 10¹⁶ m^-2).
• Dislocations of several to hundreds of nanometers in length were identified, effectively scattering phonons while maintaining carrier transport.

Conclusions:

• Heavy Te/S alloying and Cu doping in PbSe create dense dislocations, significantly reducing lattice thermal conductivity.
• The engineered microstructure enhances phonon scattering, leading to improved thermoelectric performance near room temperature.
• The developed PbSe-based material demonstrates superior thermoelectric properties compared to previous PbSe materials at low-medium temperatures.