Influence of calcination temperature on physical and optical properties of nickel chromite nanoparticles

Nickel chromite nanoparticles were prepared by sol-gel auto combustion method followed by calcination at different temperatures, 700, 900, 1100 and 1300oC for 8h. The prepared nanoparticles were characterized by XRD, SEM, EDS, FTIR and UV-Vis spectroscopy. From the XRD patterns, the Miller indices (hkl) were identified for all the prominent peaks for all the samples, it was clear that the compound crystallized according to spinel structure with a space group of Fd3m. SEM images showed non-uniform agglomerated fragments having a lot of voids and pores. UsingScherrer method, the crystallite size was calculated and found gradually increasing trend with the calcination temperature from 13.73 to 22.33 nm, where as the average grain size was increased from 140.00 to 163.46 nm with calcination temperature. FTIR spectra showed six fundamental absorption bands in the range 500 to 3470 cm-1, whereas the two absorption bands in the range 500-625 cm-1 confirmed the bonding vibrations of metal-oxygen bonds situated at octahedral and tetrahedral sites. UV-Vis spectroscopy was carried out in the wavelength range 200-800 nm and the optical band gap (Eg) was observed in the range 4.2129-4.3115 eV.