Dual doping strategy for enhancing the thermoelectric performance of Yb0.4Co4Sb12

Abstract

Yb_0.4Co₄Sb₁₂ compound is extensively studied for its superior thermoelectric properties, which are primarily attributed to the phonon-glass-electron-crystal (PGEC) approach upon Yb occupying the void-site in the unit cell. Herein, thermoelectric performances of co-doped Yb_0.4Co_3.96−xMo_xTi_0.04Sb₁₂ (x = 0, 0.02, 0.04, and 0.08) samples synthesized via a solid-state vacuum-encapsulated melt-quench-annealing method were measured in the temperature range of 300 K to 715 K. The framework of Mo⁴⁺ substituted at the Co²⁺/Co³⁺ site acted as a donor-like impurity, thereby significantly increasing the carrier concentration to 2.88 × 10²⁰ cm⁻³ for Yb_0.4Co_3.92Mo_0.04Ti_0.04Sb₁₂ at 300 K. Meanwhile, the electrical conductivity at 300 K approached a value of 756.73 S cm⁻¹ and further increased to 820 S cm⁻¹ at 711 K. The intensified point defect scattering from the dual doping strategy and enhanced grain boundary scattering simultaneously turned down the thermally active phonons to a suppressed κ_total of ∼2.11 W m⁻¹ K⁻¹ at 623 K, leading to an enhanced zT of ∼0.92 for Yb_0.4Co_3.92Mo_0.04Ti_0.04Sb₁₂, making it a promising candidate for intermediate temperature energy conversion applications.