Enhanced Thermoelectric Properties of Pd and Ni Codoped Electronegative Element-Filled Skutterudites

Electronegative element-filled skutterudites have attracted considerable attention due to their use of environmentally friendly elements and their excellent thermoelectric performance. While single-donor doping at Co or Sb sites has been shown to be thermodynamically favorable, the effects of codoping on electronegative element-filled skutterudites remain underexplored. In this study, we investigate the impact of codoping palladium (Pd) and nickel (Ni) at Co sites on the stability of the electronegative element (S) fillers within the voids of CoSb₃. A series of S_zPd_xNi_yCo_4–x–ySb₁₂ compounds were successfully synthesized, and their electrical and thermal transport properties are systematically analyzed. Our results reveal that the Hall carrier concentration, Seebeck coefficient, and Hall mobility of the S_zPd_xNi_yCo_4–x–ySb₁₂ samples lie between those of S-filled and Pd or Ni single-doped counterparts. Additionally, these compounds exhibit reduced lattice thermal conductivities due to the synergistic interaction between the S filler and Pd/Ni codopants. Notably, a peak figure of merit (zT) of 0.89 is achieved for S_0.05Pd_0.2Ni_0.2Co_3.6Sb₁₂ at 850 K.