The study of solvothermal synthesis of nano-engineered CoSb3 skutterudite thermoelectric materials

Nanostructured materials have been shown to enhance phonon scattering and improve the figure of merit of thermoelectric materials. Solvothermal syntheses of nano-engineered CoSb3 skutterudite have been studied in the present work in which CoCl2 and SbCl3 were used as precursors and NaBH4 as a reductant. Elemental, structural and morphology characterization techniques including: XRD, SEM, TEM and EDAX were used to identify and characterize the products. NaBH4 was found to be a necessary factor in forming cobalt antimonide. It was detected the products' phase transited from Sb2Co to CoSb3 in conjunction with the amount increase of NaBH4. The change of synthesis time and temperature contributed little on the products' phases under the present experimental routes. Single-phased CoSb3 skutterudites was obtained from the solvothermal syntheses combined with an acid wash. The as-prepared CoSb3 powders consist of irregular nanoparticles with 15 similar to 20 nm in size. A possible chemical mechanism was also discussed.