Thermoelectric Cu₁₂ Sb₄ S₁₃ -Based Synthetic Minerals with a Sublimation-Derived Porous Network

Pores in a solid can effectively reduce thermal conduction, but they are not favored in thermoelectric materials due to simultaneous deterioration of electrical conductivity. Conceivably, creating a porous structure may endow thermoelectric performance enhancement provided that overwhelming reduction of electrical conductivity can be suppressed. This work demonstrates such an example, in which a porous structure is formed leading to a significant enhancement in the thermoelectric figure of merit (zT). By a unique BiI₃ sublimation technique, pore networks can be introduced into tetrahedrite Cu₁₂ Sb₄ S₁₃ -based materials, accompanied by changes in their hierarchical structures. The addition of a small quantity of BiI₃ (0.7 vol%) results in a ≈72% reduction in the lattice thermal conductivity, whereas the electrical conductivity is improved due to unexpected enhanced carrier mobility. As a result, an enhanced zT of 1.15 at 723 K in porous tetrahedrite and a high conversion efficiency of 6% at ΔT = 419 K in a fabricated segmented single-leg based on this porous material are achieved. This work offers an effective way to concurrently modulate the electrical and thermal properties during the synthesis of high-performance porous thermoelectric materials.