Solid-state Janus nanoprecipitation enables amorphous-like heat conduction in crystalline Mg3Sb2-based thermoelectric materials

TL;DR

This study introduces Janus-type nanoprecipitates in Mg3Sb1.5Bi0.5, which significantly reduce lattice thermal conductivity and enhance thermoelectric performance by enabling amorphous-like heat conduction in crystalline materials.

Contribution

It reveals a novel Janus nanoprecipitation mechanism that improves thermoelectric properties by controlling phonon scattering in Mg3Sb2-based materials.

Findings

Achieved ZT of 0.6 near room temperature

Reached ZT of 1.6 at 773 K

Demonstrated amorphous-like heat conduction in crystalline materials

Abstract

Solid-state precipitation can be used to tailor materials properties, ranging from ferromagnets and catalysts to mechanical strengthening and energy storage. Thermoelectric properties can be modified by precipitation to enhance phonon scattering while retaining charge-carrier transmission. Here, we uncover unconventional dual Janus-type nanoprecipitates in Mg3Sb1.5Bi0.5 formed by side-by-side Bi- and Ge-rich appendages, in contrast to separate nanoprecipitate formation. These Janus nanoprecipitates result from local co-melting of Bi and Ge during sintering, enabling an amorphous-like lattice thermal conductivity. A precipitate size effect on phonon scattering is observed due to the balance between alloy-disorder and nanoprecipitate scattering. The thermoelectric figure-of-merit ZT reaches 0.6 near room temperature and 1.6 at 773 K. The Janus nanoprecipitation can be introduced into other materials and may act as a general property-tailoring mechanism.