Ghosh, Paromita and Mahanty, S and Raja, M W and Basu, Rajendra Nath and Maiti, Himadri Sekhar
(2007)
Structure and optical absorption of combustion-synthesized nanocrystalline LiCoO2.
Journal of Materials Research, 22 (5).
pp. 1162-1167.
ISSN 0884-2914
Abstract
Nanocrystalline LiCoO2 powders (10-50 nm) were synthesized by a citrate-nitrate combustion process followed by calcination at different temperatures (300-800 degrees C) in air. Thermogravimetric analyses indicated a sharp combustion at a low temperature of 225 degrees C, producing fine crystallites. Quantitative phase analyses from the x-ray diffractograms showed that while annealing at 500 degrees C produced mixed phases of cubic and rhombohedral LiCoO2, annealing at 800 degrees C resulted in single-phase rhombohedral LiCoO2. Electronic transitions related to the Co 3d bands were investigated by ultraviolet-visible reflectance spectra in absorbance mode and were ascribed to the Co 3d intra-band transition involving t(2g) and e(g) orbitals. The d-d transitions underwent a blue shift of about 0.3 eV as the cubic LiCoO2 transformed into the rhombohedral structure with band gap values of about 1.4 and 1.7 eV.
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