A New Material with a Composite Crystal Structure Causing Ultralow Thermal Conductivity and Outstanding Thermoelectric Properties : Tl 2 Ag 12 Te 7+δ
A new state-of-the-art thermoelectric material, Tl 2 Ag 12 Te 7+δ , which possesses an extremely low thermal conductivity of about 0.25 W m -1 K -1 and a high figure-of-merit of up to 1.1 at 525 K, was obtained using a conventional solid-state reaction approach. Its subcell is a variant of the Zr 2 Fe 12 P 7 type, but ultimately its structure was refined as a composite structure of a Tl 2 Ag 12 T