Structural and phonon modes study of nano ceramics CoAl 2 O 4 synthesized by sol-gel route

Abstract

CoAl 2 O 4 nano ceramic was successfully synthesized via sol-gel auto combustion technique and the obtained nano-sized powder is annealed at 800° C for 8h. The annealed powder is examined by x-ray diffraction (XRD) and Raman spectroscopy at room temperature. The diffraction peaks of the annealed CoAl 2 O 4 are well crystalline and correspond to cubic inverse-spinel structure with space group Fd-3m. Raman spectroscopy also confirms the formation of single phase structure. Crystallite size and the strain are obtained using Williamson-hall method and found to have values ∼17 nm and -2.41×10 -3 , respectively. The negative strain in crystal structure is attributed to the shrinking of structure in order to get stability in nano ceramics. In vibrational study we are confirming inverse spinel structure via Raman spectroscopy. The quadruplicate splitting of peak related to A 1g mode at 694 cm -1 , 715 cm -1 , 735 cm -1 and 758 cm -1 attributed to structural symmetry.