Hierarchical structures lead to high thermoelectric performance in Cum+nPb100SbmTe100Se2m (CLAST)

Abstract

Ternary compound CuSbSe₂-alloyed PbTe, Cu_mPb₁₀₀Sb_mTe₁₀₀Se_2m (CLAST), presents outstanding n-type thermoelectric transport behavior and features hierarchical Cu-based precipitates and interstitials that can balance phonon and carrier transport. Results show that a small amount of CuSbSe₂ (∼3%) alloying in CLAST can realize a room-temperature carrier concentration of ∼1.7 × 10¹⁸ cm⁻³ and then optimize the power factor, and simultaneously precipitate out embedded Cu-based nanostructures in the matrix to lower the lattice thermal conductivity. Additionally, extra Cu atoms adding in CLAST can form interstitials and further improve both the carrier concentration to ∼3.0 × 10¹⁸ cm⁻³ and carrier mobility to ∼1227.8 cm² V⁻¹ s⁻¹ at room temperature, which benefits a maximum power factor of ∼20.0 μW cm⁻¹ K⁻² in Cu_3.3Pb₁₀₀Sb₃Te₁₀₀Se₆. Moreover, the Cu interstitials together with massive Cu-based nanoprecipitates can strongly scatter a wide set of phonons, and largely lower the lattice thermal conductivity to ∼0.44 W m⁻¹ K⁻¹ in Cu_3.4Pb₁₀₀Sb₃Te₁₀₀Se₆ at 623 K. Finally, these Cu-based hierarchical structures in CLAST samples can synergistically optimize the phonon and carrier transport properties and contribute to a high ZT of ∼0.5 at 300 K and a peak ZT of ∼1.4 at 723 K. A remarkably high ZT_ave of ∼0.94 at 300–723 K is achieved in Cu_3.3Pb₁₀₀Sb₃Te₁₀₀Se₆ due to high ZT values in the low temperature range, outperforming other high-performance n-type PbTe-based thermoelectric materials.