Thangaraj Pandiyarajan, Mauro L. Baesso e Balasubramanian Karthikeyan

The European Physical Journal D – Volume: 68: Issue: 2; Pages: 28-36; DOI: 10.1140/epjd/e2013-40363-3

We present secondary phase identification studies on Cr doped ZnO nanoparticles prepared by the sol-gel method. X-ray diffraction analysis confirms the formation of chromium oxides and there is found to be an increase of lattice parameter with thermal annealing. Scanning electron microscopic studies show the increase in the crystalline nature and particle size. Optical absorption measurements of the as prepared sample exhibit a strong band at 356 nm due to the free exciton absorption of the ZnO nanoparticles. An absorption band at 277 nm is due to the 3T1 → 3T2 transition in Cr4+ ions which appears only for the annealed samples. Photoluminescence studies show that deep level emission is completely suppressed after Cr2O3 formation/thermal annealing. Raman and FTIR spectra reveal formation of the Cr2O3 phase. Thermal annealing leads to the increase of crystalline nature which gives an enhancement to the Raman modes.