Effect of Sn doping at Sb sites on the structural and optical properties of Co₂Sb₆ nanostructures

Nanostructured thermoelectric Skutterudite-based compounds Co₂Sb_6-xSnx (x= 0.15, 0.2, 0.25, 0.3) with different concentration of Sn were synthesized by hydro-/solvothermal method and annealed at 300° C for 5 hrs in inert atmosphere. Surface morphology analysis shows the formation of square block shaped nanostructures with particle size, 50-70 nm and the chemical analysis confirms the purity of the samples. Structural analysis by powder X-ray diffraction (pXRD) depicts cubic structure of CoSb₃ and also confirms the successful occupation of Sn into Sb sites without distorting the crystal structure. The vibration modes corresponding to Co-Sb bonding, cobalt complex and Co-Sn bonding can be observed below 1000 cm⁻¹. Sn filled Co₂Sb₆ nanostructures show absorption bands in the wavelength range of 260-270 nm.