Realize High Thermoelectric Properties in n-Type Bi₂Te_2.7Se_0.3/Y₂O₃ Nanocomposites by Constructing Heterointerfaces

Due to the excellent thermoelectric performance, bismuth telluride (Bi2Te3) compounds are highly promising for the thermoelectric conversion in the room temperature range. However, the inferior thermoelectric performance of the n-type leg severely restricts the applications of Bi2Te3-based thermoelectric couples. Herein, n-type Bi2Te2.7Se0.3 (BTS)-based thermoelectric materials incorporated with nanosized Y2O3 (0.5–3 wt %) are prepared and their thermoelectric properties are systematically studied. The dramatically improved thermoelectric performance is ascribed to the realization of a multiscale feature of Y2O3 nanoparticle (NP)-induced interfacial decorations distributed along grain boundaries, which creates massive BTS/Y2O3 interfaces for the manipulation of carrier and phonon transport properties. The geometric phase analysis is employed to further confirm the condition of local strain in the BTS composite incorporated with Y2O3 NPs. Due to the presence of heterointerfaces and high density of dislocations in BTS matrices, the minimum lattice thermal conductivity (κl) of the nanocomposites (NCs) is dramatically suppressed from 0.76 to 0.37 W m–1 K–1. With the incorporation of 3 wt % Y2O3 NPs, the Vickers hardness of the BTS/Y2O3 NC is increased by about 32%. Overall, the BTS + 1.5 wt % Y2O3 NC maintains excellent thermoelectric properties (ZTave = 1.1) in the whole operative temperature range (300–500 K). The present strategy of implementing high-density heterogeneous interfaces by Y2O3 NP addition offers an applicable pathway for fabricating high-performance thermoelectric materials with both optimized thermoelectric properties and mechanical properties.