Thermoelectric Properties of the Thallium-Tellurium Binary Compounds

Abstract

We are paying attention to extremely low thermal conductivity (κ) materials which have a potential to be next generation thermoelectric materials. Most of the extremely low κ materials that have been reported so far are ternary thallium tellurides such as Ag-Tl-Te ternary system. However, as for Tl-Te binary system, the thermoelectric properties have been scarcely reported. In the present study, the Tl-Te binary compounds, Tl₂Te, Tl₅Te₃, TlTe, and Tl₂Te₃, were prepared and their thermoelectric properties were investigated. The κ of TlTe was relatively high (approximately 4 Wm⁻¹K⁻¹ at 300 K), while those of Tl₂Te and Tl₂Te₃ were extremely low (∼0.5 Wm⁻¹K⁻¹ at 300 K). These compounds indicated relatively high thermoelectric figure of merit ZT, e.g., Tl₂Te showed the highest value of 0.2 at 586 K.