Synergistic optimization of Seebeck coefficient and lattice thermal conductivity in p-type Yb-filled skutterudites

In thermoelectric materials, electrical transport and thermal transport are strongly coupled. Filled skutterudite materials enable electrical transport through their atomic framework, while the filler atoms scatter phonons, making them typical "electron crystals-phonon glasses". This study systematically investigates the influence of Yb filling amount on the microstructure and thermoelectric transport properties of p-type skutterudite materials YbₓFe₃CoSb₁₂. X-ray diffraction (XRD) results show that all samples exhibit a main phase with cubic skutterudite structure. When x ≥ 0.9, the impurity phases of FeSb₂ and Sb significantly decrease, and the purity of the main phase is remarkably improved. Scanning electron microscopy (SEM) observations reveal that Yb doping promotes grain homogenization and densification, and energy-dispersive X-ray spectroscopy (EDS) analysis confirms that the uniformity of Yb element distribution is closely related to the doping level. Thermoelectric property measurements indicate that appropriate Yb filling significantly enhances the Seebeck coefficient, reaching 160 μV·K⁻¹ at 800 K for x = 1.0 Meanwhile, the x = 0.9 sample exhibits excellent electrical conductivity and power factor. Thermal conductivity analysis shows that Yb filling effectively reduces the lattice thermal conductivity, with the lattice thermal conductivity (κ_L) of the x = 1.0 sample decreasing to 1.2 W·m⁻¹·K⁻¹ at 800 K. Ultimately, the x = 1.0 sample achieves a maximum zT value of 0.74 at 750 K, representing an improvement of approximately 12% compared to previously reported results. These findings validate the synergistic advantages of Yb filling combined with the melt-hot pressing process in enhancing the comprehensive thermoelectric performance of p-type skutterudite materials, providing an effective pathway for structural regulation and engineering preparation of high-performance thermoelectric materials.