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

The anisotropy of the thermoelectric properties of Bi2Te3-xSex (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 rho and thermal conductivity k of Bi2Te3-xSex are obtained. For example, the resistivity ratio rho(p)/rho(n) (here subscript n and p denote the directions normal and parallel to the pressing direction, respectively) and thermal conductivity ratio kp/kn for Bi2Te3-xSex 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 ZTn of -0.7 is obtained in the temperature range of 440-470 K for Bi2Te2.1Se0.9. Moreover, the maximum ZT(p) for Bi2Te2.6Se0.4 is similar to 0.6 in the temperature range from 400 to 470 K.