Hierarchical Structuring to Break the Amorphous Limit of Lattice Thermal Conductivity in High-Performance SnTe-Based Thermoelectrics

Minimizing lattice thermal conductivity, κl, of thermoelectric materials is an effective strategy to enhance their figure-of-merit, zT. However, the amorphous limit of κl affects the ceiling of the attainable zT. Herein, we fabricate hierarchical structures by using an in situ microwave synthesis to break the amorphous limit of κl for achieving a high zT in (Sn0.985In0.015Te)1–x(AgCl)x alloys. Our results from detailed electron microscopy characterizations suggest that the as-sintered (Sn0.985In0.015Te)1–x(AgCl)x alloys contain a range of lattice imperfections, including microsized grains with dense grain boundaries, nanopores with sizes from several to hundreds of nanometers, and nanoscale precipitates, which result in strong phonon scatterings and in turn lead to a minimized κl of 0.245 W m–1 K–1. Moreover, the calculated band structures reveal the introduction of resonance level by In doping, which dramatically enhances the electrical transport properties to ensure a high power factor of 26.4 μW cm–1 K–2 at 823 K and a maximum zT of 0.86 (823 K) in hierarchically structured (Sn0.985In0.015Te)0.90(AgCl)0.10. This work provides a new approach to modulate the hierarchical structures for optimizing thermal and electronic transport properties.