Effect of nominal Sb2Te3 content on thermoelectric properties of p-type (Bi2Te3)x(Sb2Te3)1−x alloys by MA–HP

Abstract

p-type (Bi2Te3)x(Sb2Te3)1−x alloys with homogeneous and fine microstructure were prepared by the mechanical alloying–hot pressing (MA–HP) method in the present work. X-ray diffraction, energy dispersive x-ray spectroscopy, scanning electron microscope–backscattered electron imaging were performed to characterize the MA–HPed materials. The effect of nominal Sb2Te3 content on mechanical and thermoelectric properties of the (Bi2Te3)x(Sb2Te3)1−x was investigated. Thermoelectric properties were measured at 300 K. By increasing the nominal molar fraction of Sb2Te3 from 0.7 to 0.9, the carrier concentration (nc) increased obviously from 0.43 × 1019 to 3.08 × 1019 cm−3; however, carrier mobility (μ) fluctuated between 198.0 and 285.5 cm2 V−1 s−1, and the Seebeck coefficient (α) and electrical resistivity (ρ) decreased acutely. The thermal conductivity (κ) increased with increase in the nominal Sb2Te3 content, while the lattice thermal conductivity (κph) decreased abruptly from 0.820 to 0.297 W m−1 K−1. When the nominal molar fraction of Sb2Te3 was 0.8, the resultant maximum power factor (PF) and thermoelectric figure of merit (Z) of the p-type (Bi2Te3)x(Sb2Te3)1−x alloys reached 3.81 × 10−3 W m−1 K−2 and 3.23 × 10−3 K−1 at 300 K, respectively. The bending strength reached 64 MPa, which was 3–5 times larger than that of single crystal materials.