Thermoelectric Properties of Thallium Compounds with Extremely Low Thermal Conductivity

Abstract

Polycrystalline samples of thallium compounds, Tl₉BiTe₆, TlBiTe₂, TlSbTe₂, and AgTlTe were prepared and the thermoelectric properties such as the electrical resistivity, Seebeck coefficient, and thermal conductivity were measured. The Seebeck coefficients of Tl₉BiTe₆, TlSbTe₂, and AgTlTe are positive, while that of TlBiTe₂ is negative. The thermal conductivities of these thallium compounds are very low compared with state-of-the-art thermoelectric materials. Especially, AgTlTe indicates extremely low value, 0.25 Wm⁻¹K⁻¹ at room temperature. The dimensionless figure of merit ZT of thallium compounds are relatively high due to their very low thermal conductivities. The maximum value of ZT is obtained for TlSbTe₂ as 0.87 at 715 K.