Avoided Crossing Phonons Realizes High-Performance Single-Crystalline β-Zn₄Sb₃ Thermoelectrics.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Thermoelectrics

Background:

• Ultralow lattice thermal conductivity (κL) is crucial for efficient thermoelectric materials.
• β-Zn₄Sb₃ exhibits promising thermoelectric properties but requires mechanism elucidation.

Purpose of the Study:

• To investigate the mechanisms responsible for ultralow κL in β-Zn₄Sb₃ single crystals.
• To provide experimental evidence for phonon interactions and their impact on thermoelectric performance.

Main Methods:

• Inelastic neutron scattering (INS) to analyze phonon behaviors and interactions.
• Transmission electron microscopy (TEM) for structural characterization.
• Thermoelectric property measurements.

Main Results:

• Experimental evidence of avoided crossing between rattlers and acoustic phonons in β-Zn₄Sb₃.
• Ultralow κL attributed to rattler-phonon avoided crossings and grain-boundary-free structure.
• Single-crystalline β-Zn₄Sb₃ demonstrated superior thermoelectric performance over polycrystalline forms.
• Undoped single-leg β-Zn₄Sb₃ achieved 1.4% conversion efficiency (η) at a 200 K temperature gradient.

Conclusions:

• Rattler-phonon avoided crossings are a key mechanism for achieving ultralow κL in β-Zn₄Sb₃.
• Crystallinity control and dilute doping significantly enhance thermoelectric figure-of-merit (zT).
• Single-crystalline β-Zn₄Sb₃ offers a promising pathway for high-performance thermoelectric devices.