Demonstration of ultrahigh thermoelectric efficiency of ∼7.3% in Mg3Sb2/MgAgSb module for low-temperature energy harvesting

Thermoelectric harvesting of low-temperature waste heat offers great opportunities for sustainable energy production. However, the investigations of related thermoelectric materials and modules remain sluggish. Here, we reported a great advance in the n-type Mg3Sb1.5Bi0.5 system by minor Cu additions. Some Cu atoms preferentially occupy interstitial sites within the Mg3Sb2 lattice and significantly modified phonon modes via filling in the phonon gap and increased anharmonic phonon scattering, thereby leading to the anomalously low thermal conductivity. Simultaneously, the detrimental behavior of thermally activated electrical conductivity was completely eliminated through grain-boundary complexion engineering. These two critical roles contributed to the remarkable improvement of zT Based on this developed high-performance material coupled with p-type alpha-MgAgSb-based material, a fabricated thermoelectric module rivaling long-time champion Bi2Te3, demonstrated a record-high conversion efficiency 7,3% at the hot-side temperature of 593 K. These results pave the way for low-temperature thermoelectric harvesting.

Automated summary

Researchers have made significant advancements in thermoelectric materials by adding minor amounts of Cu to the Mg3Sb1.5Bi0.5 system, leading to improved thermoelectric performance and reduced thermal conductivity. Through grain-boundary engineering, the detrimental effects of thermally activated electrical conductivity were successfully eliminated. The fabricated thermoelectric module, when combined with a p-type alpha-MgAgSb-based material, showed promising potential for low-temperature thermoelectric harvesting.