High-performance bulk thermoelectrics with all-scale hierarchical architectures.

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Thermoelectric materials offer direct heat-to-electricity conversion, crucial for waste heat recovery.
• Current materials are limited by a low figure of merit (ZT), hindering practical applications.
• Nanostructuring improves ZT by reducing thermal conductivity but doesn't fully scatter all heat carriers.

Purpose of the Study:

• To investigate scattering of heat-carrying phonons across multiple length scales in thermoelectric materials.
• To enhance thermoelectric performance by optimizing mesoscale architecture.
• To achieve a figure of merit (ZT) exceeding the critical threshold of 2.

Main Methods:

• Developed a panoscopic approach to phonon scattering, integrating atomic, nanoscale, and mesoscale strategies.
• Utilized endotaxial nanostructuring with SrTe and mesostructuring via powder processing and spark plasma sintering in PbTe.
• Controlled hierarchical architecture to scatter phonons with long mean free paths.

Main Results:

• Achieved maximum reduction in lattice thermal conductivity by scattering phonons across integrated length scales.
• Demonstrated a record figure of merit (ZT) of ~2.2 at 915 Kelvin in p-type PbTe.
• Exceeded the desired ZT threshold of 2, indicating significant improvement in thermoelectric performance.

Conclusions:

• Multiscale hierarchical architecture is essential for optimizing phonon scattering in bulk thermoelectrics.
• The panoscopic approach offers a viable strategy for developing high-performance thermoelectric materials.
• This advancement presents a realistic prospect for efficient recovery of significant amounts of waste heat.