Enhanced thermoelectric performance of n-type Bi₂Te_2.7Se_0.3 via a simple liquid-assisted shear exfoliation

A liquid-assisted shear exfoliation (LASE) as a new powder metallurgy method coupled with spark plasma sintering (SPS) was applied for n-type Bi₂Te_2.7Se_0.3 and the effects on microstructure and anisotropic transport properties were investigated. Results revealed an effective reduction of average grain size due to LASE and a high texturing in the bulks. Moreover, along the in-plane direction, electrical conductivity was increased noticeably due to an enhanced carrier concentration, leading to a significantly improved power factor of 25 μW cm^–1 K^–2 at 303 K. Meanwhile, the total thermal conductivity was reduced effectively owing to reduction both in lattice component due to enhanced phonon scattering with the grain size reduction, and in the bipolar component inhibited by the increased carrier concentration. Ultimately, a peak thermoelectric figure of merit (ZT) value of 0.83 was obtained at 448 K along the in-plane direction, increased by 95% compared with the pristine one. These results demonstrate the LASE process as a useful assistant method for enhancing the TE performance of layered materials.