SnTe–AgBiTe2 as an efficient thermoelectric material with low thermal conductivity

Abstract

SnTe is an intriguing alternative to its sister compound PbTe in thermoelectric energy conversion because of their electronic and structural similarity; however, it is challenging to optimize its thermoelectric performance to the level of PbTe because of the difficulties in decreasing its intrinsically large hole population and high thermal conductivity arising from the tin vacancies. We demonstrate here that by alloying some AgBiTe₂ in SnTe, thus forming AgSn_xBiTe_x+2 compositions the hole concentration can be duly decreased because of the high efficiency of Bi as an electron donor. The lattice thermal conductivity is also decreased due to the strong scattering of phonons (by point defect scattering as well as Ag-rich nanostructures) to achieve a value of ∼0.7 W m⁻¹ K⁻¹ at ∼750 K. As a result, a high thermoelectric figure ZT of merit of ∼1.1 at 775 K is achieved by chemical composition optimization (×∼15), making lead free SnTe–AgBiTe₂ a promising thermoelectric material.