Dual-approach enhancement of thermoelectric performance in Yb-filled skutterudites: In-situ pore architecture engineering and carrier concentration optimization

While Yb-filled skutterudites are promising candidates as mid-temperature thermoelectric materials, their practical application remains constrained by inadequate performance. In this study, we propose a dual optimization strategy to modulate the electro-thermal transport performance. The as-cast ingots underwent initial densification via hot-pressing, followed by pressureless annealing. By utilizing the solid solution of the YbSb₂ phase, we not only increase the Yb filling fraction but also achieve precise pore architecture engineering through volume changes induced by phase transformation. Notably, the integration of Yb filling and a prolonged 72-hour annealing treatment not only optimized carrier concentration but also dramatically inhibited phonon propagation, leading to a 57 % reduction in lattice thermal conductivity at 773 K. Thus, the optimized Yb_0.3Co₄Sb₁₂ sample demonstrated enhanced thermoelectric performance, attaining a peak ZT value of 1.44 at 873 K. This work provides fundamental insights into the synergistic improvement of thermoelectric properties in filled skutterudites.