Nano-precipitation and carrier optimization synergistically yielding high-performance n-type Bi2Te3 thermoelectrics

Abstract

The bismuth-tellurides have never ceased as the best candidates for thermoelectric (TE) coolers since the beginning of manufactures in the 1960s. As the years passed, the effort in boosting their performance continues abreast of breakthroughs in the conversion efficiencies with the occasional setbacks from the n-type alloys. Herein, a synergistic approach combining the phase diagram engineering and the carrier optimization overcomes the long-existing obstacle, eliciting an outperforming n-type Ag–Bi2Te3. The Ag0.03Bi2Te2.97 alloy attains a high figure-of-merit zT = 1.4 at 363 K and a superior averaged zTave = 1.1 within 300 K–500 K. The phase diagram pinpoints a high-zT zone whose boundary coincides with the maximal Ag solubility. A close-up upon the best-performing Ag0.03Bi2Te2.97 reveals the presence of Ag2Te nano-precipitates, explaining its low-lying κL alongside the remarkable enhancement in its power factor PF = S2ρ−1. The avenue paved by the thermodynamic route essentially revives the TE research field, in which more potential candidates are awaiting further discovery.