Thermoelectric properties of the tetradymite-type Bi2Te2S–Sb2Te2S solid solution

The thermoelectric properties of the tetradymite-type Bi2−xSbxTe2S solid solution (0 ≤ x ≤ 2) are reported for the temperature range 5–300 K. The properties of non-stoichiometric, Cl and Sn doped n- and p-type variants are reported as well. The Seebeck coefficients for these materials range from −170 to +270 μV K−1 while the resistivities range from those of semimetals, 2 mΩ cm, to semiconductors, >1000 mΩ cm. Thermal conductivities were low for most compositions, typically 1.5 W m−1 K−1. Nominally undoped Bi2Te2S shows the highest thermoelectric efficiency amongst the tested materials with a ZT = 0.26 at 300 K that decreased to 0.04 at 100 K. The crystal structure of Sb2Te2S, a novel tetradymite-type material, is also reported.