High?Pressure?Sintering?Induced Microstructural Engineering for an Ultimate Phonon Scattering of Thermoelectric Half?Heusler Compounds

Thermal management is of vital importance in various modern technologies such as portable electronics, photovoltaics, and thermoelectric devices. Impeding phonon transport remains one the most challenging tasks for improving performance certain materials half-Heusler compounds. Herein, a significant reduction lattice thermal conductivity (?L) achieved by applying pressure ?1 GPa to sinter broad range Contrasting with common sintering less than 100 MPa, gigapascal-level enables densification at lower temperature, thus greatly modifying structural characteristics an intensified scattering. A maximum ?L ?83% realized HfCoSb from 14 2.5 W m?1 K?1 300 K more 95% relative density. The low originates remarkable grain-size refinement below nm together abundant in-grain defects, determined microscopy investigations. This work uncovers properties compounds under unconventional microstructures, showing potential high-pressure compaction advancing materials.