Electronegative S/Se co-filled and Fe-substituted p-type skutterudites prepared by high-temperature and high-pressure technique

Although n-type skutterudites modified by electropositive fillers have been extensively studied, research on p-type skutterudites filled with electronegative elements remains scarce. In this work, a series of sulfur/selenium (S/Se) co-filled and iron (Fe)-doped p-type skutterudite samples with a nominal composition of S_0.1-xSe_xFe_0.2Co_3.8Sb_12 (x= 0.025, 0.05, 0.075, 0.1) were rapidly synthesized via the high-temperature and high-pressure (HPHT) technique. Phase analysis indicates that the as-prepared samples possess a pure skutterudite structure without obvious impurity phases. Microstructural observations demonstrate that S/Se co-filling can effectively regulate the grain morphology and the evolution of grain size. Electrical transport measurements reveal that Fe substitution successfully induces p-type conductivity and optimizes the carrier transport behavior. Meanwhile, S/Se co-filling introduces strong phonon scattering, which significantly reduces the lattice thermal conductivity. For the optimal S_0.075Se_0.025Fe_0.2Co_3.8Sb_12, fitting based on the Debye-Callaway model confirms that the resonant frequencies of S and Se are 43.96 cm^-1 and 35 cm^-1, respectively. Finally, the S_0.075Se_0.025Fe_0.2Co_3.8Sb_12 sample achieves a maximum zT value of approximately 0.22 at 673.15 K. This study provides a feasible strategy for constructing electronegative element co-filled p-type skutterudites and deepens the understanding of multiscale phonon scattering mechanisms in thermoelectric materials.