Enhancing the thermoelectric performance of n-type Bi2Te2.7Se0.3 through the incorporation of Ag9AlSe6 inclusions

Abstract

Bi₂Te_2.7Se_0.3 (BTS) is the best commercial n-type thermoelectric alloy at near room temperature. However, as compared to its p-type counterpart, its figure of merit (ZT) and energy conversion efficiency are relatively low. Thus, the improvement of ZT for n-type BTS is imperative. Here, we show that the incorporation of the Ag₉AlSe₆ phase into BTS can remarkably reduce lattice thermal conductivity, due to the intensified phonon scattering from Ag₉AlSe₆ nanoparticles and interfaces. Meanwhile, the Seebeck coefficient is enhanced due to the decreased carrier concentration. The suppressed thermal conductivity leads to ZT_max = ∼1.2 at 423 K for the BTS-0.35 vol% Ag₉AlSe₆ sample, a ∼38% increase compared to that for pristine BTS. Consequently, a high average ZT_ave ∼ 1.1 (300 K–473 K) is reached, indicating that the incorporation of the Ag₉AlSe₆ nanophase is an effective way to improve the thermoelectric performance of BTS.