Enhancing thermoelectric performance of n-type Bi2Te2.7Se0.3 through the incorporation of MnSb2Se4 nanoinclusions

Bi2Te3-based alloys are the state of art thermoelectric materials for near-room temperature applications. However, the figure of merit, ZT, of n-type Bi2Te2.7Se0.3 (BTS) is not large enough to its wide applications, and previous studies seldom involve incorporation of Mn-based alloys in BTS-based composites. Here, we show that through dispersion of transition-metal selenide MnSb2Se4 (MSS) into BTS can simultaneously increase the power factor (PF) and reduce lattice thermal conductivity (κL) greatly. Experimental evidences show that increased PF comes from enhanced thermopower due to energy filtering effect; while the reduced κL originates mainly from intensified phonon scattering by the MSS nanoinclusion and dislocations. As a result, a large ZTmax = 1.23 (at 345 K) and an average ZTave ∼ 1.15 (300 K-473 K) are achieved for BTS/0.50 wt% MSS sample, which is respectively ∼ 48% and ∼ 42% larger than those of pristine BTS. In addition, this sample shows better mechanical properties with its Vickers hardness being increased by 17%. Present results demonstrate that incorporation of transition-metal selenides, such as MSS, is a promising way to improving thermoelectric performance as well as mechanical properties of BTS.