Structural And Optical Studies Of Nanocrystalline ZnCr2O4 And CoCr2O4 Spinel

Chromites ACr(2)O(4) nanoparticles (A = Zn, Co) annealed at 800 degrees C/8 h were successfully prepared by sol gel auto combustion (SGAC) method in the presence of nitrate ions and using citric acid as catalysis. The observed X-ray diffraction (XRD) data confirms that all the prepared samples are indexed in cubic crystal structure (space group Fd3m). The average particle size of the nanomaterial ZnCr2O4 and CoCr2O4 calculated from XRD was found in the range 19-21 nm. Four Raman active phonon modes observed around at 185, 514, 607 and 691 cm(-1) as F-2g ((1)), F-2g ((2)), F-2g ((3)) and A(1g) for ZnCr2O4 and three Raman active modes observed at 197, 514 and 685 cm(-1) as F-2g ((1)), E-g and A(1g) respectively, for CoCr2O4. The band gap energy of ZnCr2O4 and CoCr2O4 powder was determined by absorption spectroscopy in ultraviolet-visible range and was found to be 3.81 eV and 3.23 eV for direct band gap respectively.