Preparation and Thermoelectric Properties of Doped Bi2Te3-Bi2Se3 Solid Solutions

Since Bi₂Te₃ and Bi₂Se₃ have the same crystal structure, they form a homogeneous solid solution. Therefore, the thermal conductivity of the solid solution can be reduced by phonon scattering. The thermoelectric figure of merit can be improved by controlling the carrier concentration through doping. In this study, Bi₂Te_2.85Se_0.15:D _m (D: dopants such as I, Cu, Ag, Ni, Zn) solid solutions were prepared by encapsulated melting and hot pressing. All specimens exhibited n-type conduction in the measured temperature range (323 K to 523 K), and their electrical conductivities decreased slightly with increasing temperature. The undoped solid solution showed a carrier concentration of 7.37 × 10¹⁹ cm^?3, power factor of 2.1 mW m^?1 K^?1, and figure of merit of 0.56 at 323 K. The figure of merit (ZT) was improved due to the increased power factor by I, Cu, and Ag dopings, and maximum ZT values were obtained as 0.76 at 323 K for Bi₂Te_2.85Se_0.15:Cu_0.01 and 0.90 at 423 K for Bi₂Te_2.85Se_0.15:I_0.005. However, the thermoelectric properties of Ni- and Zn-doped solid solutions were not enhanced.