Thermoelectric properties of Tl2SnTe5 and Tl2GeTe5

Abstract
We report on the thermoelectric properties of two ternary tellurides with known crystal structures. Both compounds have a very low lattice thermal conductivity. Tl2SnTe5 appears to have a p-type figure of merit about the same as that of Bi2Te3, the best thermoelectric material among binary compounds. We have synthesized mainly polycrystalline samples, but a few small crystals have been grown and used for electrical measurements. Prospects for further improvement of these materials are discussed.