Solvothermal synthesis of nano-sized skutterudite Co4−xFexSb12 powders

Nanostructuring is one of the effective approaches to lower the thermal conductivity of thermoelectric materials for improving its figure of merit. The nano-sized uniform skutterudite Co4−xFexSb12 (x = 0, 0.3, 0.5, 0.8 and 1.0) thermoelectric powders were synthesized in triethylene glycol solution by using CoCl2, FeCl3 and SbCl3 as precursors and NaBH4 as reductant. Different synthesis conditions were studied to pursue pure and uniform skutterudite CoSb3 powders. The mechanism of formation and growth of CoSb3 particles were discussed based on the thermodynamics assessment of the Co–Sb system. The powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and energy-dispersive X-ray (EDX) analysis. Experiment shows that a Fe-doped skutterudite Co4−xFexSb12 single phase was obtained at 290 °C for 12 h. The powders are of spherical form, small and uniform. As x increases from 0 to 1.0, the lattice parameter of Co4−xFexSb12 increases from a = 0.9044 to 0.9060 nm, and the particle size increases from 10 to 20 nm.