Optimization of the Telluride Tl 10– x – y Sn x Bi y Te 6 for the Thermoelectric Energy Conversion

We present the thermoelectric properties of the quaternary telluride series Tl 10– x – y Sn x Bi y Te 6 including Seebeck coefficient ( S ), electrical conductivity ( σ ), and thermal conductivity ( κ ). Three different Tl concentrations, namely 9, 8.67, and 8.33 Tl per formula unit, were selected followed by variations of the Sn:Bi ratio to tune the properties at each Tl concentration. Additionally, crystal structure data and electronic structure calculations were used to model the data and support the findings. The Tl 9 (Sn, Bi)Te 6 system was found to have the highest power factor ( S 2 σ ) displaying a value of 8.1 μW · cm –1 · K –2 at 587 K, realized with Tl 9 Sn 0.2 Bi 0.8 Te 6 . Tl 8.67 Sn 0.50 Bi 0.83 Te 6 however, displays values closer to 4 μW · cm –1 · K –2 at comparable temperatures. Ultimately, the thermoelectric Figure‐of‐merit was determined to reach a competitive 0.6 at 575 K and 525 K for Tl 8.33 Sn 1.12 Bi 0.55 Te 6 and Tl 8.67 Sn 0.50 Bi 0.83 Te 6 , respectively, thereby outperforming the ternary variants Tl 10– x Sn x Te 6 .