Anisotropic Thermoelectric Properties of <i>n</i>-Type Te-Free (Bi, Sb)<sub>2</sub>Se<sub>3</sub> with Orthorhombic Structure
Teng Fang, Feng Li, Yehao Wu, Qi Zhang, Xinbing Zhao, Tiejun Zhu
Abstract
Bi2Se3, a sister compound of the best room-temperature thermoelectric (TE) Bi2Te3, has been proven to undergo a transition from a rhombohedral phase to an orthorhombic phase by Sb-alloying. Te-free Bi2–xSbxSe3 with an orthorhombic structure exhibits excellent TE performance in the midtemperature range. In this work, anisotropic transport properties of bulk polycrystalline n-type Bi2–xSbxSe3 (x = 0.8, 1.0) samples near phase transition composition are systematically studied. Due to the similar anisotropic behavior between electrical conductivity and thermal conductivity, the I-doped Bi2–xSbxSe3 samples show almost the same zT values along the in-plane and out-of-plane directions. Furthermore, n-type I-doped Bi2–xSbxSe3 is also prepared by zone-melting in order to further increase the carrier mobility and TE performance. The results show that the increase in thermal conductivity exceeds the enhancement in electrical transport properties, resulting in lower zT values.