Synthesis, structure and optical properties of Indium filled CoSb₃ nanomaterials

The nano-sized In_yCoSb₃ skutterudites (y = 0.0125, 0.025, 0.0375 and 0.0625) were synthesized by solvo-/hydrothermal method at 240 °C for 24 hours. The surface morphology of as-synthesized samples analyzed by Field Emission Scanning Electron Microscope (FESEM) shows nanoparticles with size of around 50 nm depicting narrow size distribution and Electron X-ray diffraction spectroscopy (EDX) spectrum confirms the purity of the In-filled CoSb₃ nanomaterials. The powder X-ray diffraction (pXRD) pattern reveals all the compositions showing diffraction peaks indexed to cubic phase of CoSb₃ with Space group ${\rm{Im}}\bar{3}$. However, no significant variation in the pXRD pattern of In filled CoSb₃ as compared to pure CoSb₃ justifies the successful filling of voids in cage-like structure of CoSb₃ with Indium. FTIR spectra of In filled CoSb₃ presents vibration modes below 1000 cm⁻¹ corresponding to Co-Sb bonding and Cobalt complex. A significance of In filling into CoSb₃ structure is also evident. A wide absorption has been witnessed from UV region to large part of visible region, hence indicating the effect of nanoparticle, agglomeration and filling.