Thermoelectric properties of electronegatively filled SyCo4-xNixSb12 skutterudites

Electronegative filling has been revealed to effectively reduce the lattice thermal conductivity and optimize the thermoelectric performance of skutterudites. However, experimental data related to rattling-mode vibrations are still not available. In this work, more S atoms were filled into the voids of CoSb3 along with substitution of Ni at Co-sites to better observe the rattling-mode vibrations due to charge compensation. Rattling-mode vibrations around 54 cm(-1) were detected unambiguously by Raman scattering spectroscopy, confirming the origins of the significant dropping of the lattice thermal conductivity. The proposed study validated Raman scattering spectroscopy as a convenient technique for studying rattling-mode vibrations of electronegatively filled skutterudites. The results also showed that the Ni solubility in skutterudites was increased with S filling, which was effective for adjusting and controlling the carrier concentrations. A record-high carrier concentration of 3.99 x 10(21) cm(-3) was achieved.