Thermoelectric anisotropy of n-type Bi2Te3−xSex prepared by spark plasma sintering

Abstract

The anisotropy of the thermoelectric properties of Bi₂Te_3−xSe_x (0.3 ≤ x ≤ 0.9) is investigated at temperatures from 300 to 523 K. The results indicate that due to the anisotropic microstructures, the anisotropic resistivity ρ and thermal conductivity κ of Bi₂Te_3−xSe_x are obtained. For example, the resistivity ratio ρ_p/ρ_n (here subscript n and p denote the directions normal and parallel to the pressing direction, respectively) and thermal conductivity ratio κ_p/κ_n for Bi₂Te_3−xSe_x are around 1.55–2.25 and 0.53–0.79, respectively. As a result, a highly anisotropic figure of merit (ZT) is obtained. A maximum ZT_n of ∼0.7 is obtained in the temperature range of 440–470 K for Bi₂Te_2.1Se_0.9. Moreover, the maximum ZT_p for Bi₂Te_2.6Se_0.4 is ∼0.6 in the temperature range from 400 to 470 K.