Complex chalcogenides as thermoelectric materials: A solid state chemistry approach

A solid state chemical approach to discover new mateials with enhanced thermoelectric properties is described. The aim is to construct three-dimensional bismuth chalcogenide framework structures which contain ionically interacting alkali or alkaline earth atoms. The alkali atoms tend to have soft "rattling" type phonon modes which result in very low thermal conductivity in these materials. Another desirable feature in this class of compounds is the low crystal symmetry and narrow band-gaps. Several promising materials such as BaBiTc₃, KBi_6.33S₁₀, K₂Bi₈S₁₃, β-K₂Bi₈Se₁₃, K_2.5Bi_8.5Se₁₄, Ba₄Bi₆Se₁₃, Eu₂Pb₂Bi₆Se₁₃, A_1-xPb_4-2xSb_7-xSe₁₅ (A=K, Rb), and CsBi₄Te₆ are described.