Nanostructured CeO 2 Thin Films Prepared by the Sol-Gel Dip-Coating Method with Anomalous Behavior of Crystallite Size and Bandgap

• Published in: Journal of nanomaterials 2019-10, Vol.2019, p.1-8
• Main Authors: Acosta-Silva, Y. J., Toledano-Ayala, M., Torres-Delgado, G., Torres-Pacheco, I., Méndez-López, A., Castanedo-Pérez, R., Zelaya-Ángel, O.
• Format: Article
• Language: English
• ISSN: 1687-4110; 1687-4129
• DOI: 10.1155/2019/5413134

Amorphous CeO 2 thin films were deposited by a dip-coating method on Corning glass substrates and annealed for one hour at the temperatures ( T ) of 250, 450, and 550°C in air for crystallization. The precursor solution was prepared by dissolving cerium acetate in methanol, lactic acid, glycerol, and trimethylamine at 55°C. X-ray diffraction (XRD) patterns showed the cubic structure of CeO 2 . From XRD data and employing the Scherrer formula, the crystallite size (CS) was calculated to be within the 4.0 ± 0.5 to 10 ± 1   n m interval. SEM micrographs revealed cracks of the films annealed at 250 and 450°C, even though for 550°C, the film shows a homogeneous morphology free of cracks. CS increases (from 4.0 to 10 nm) and thickness decreases (from 217 to 182 nm) when T increases. The UV-vis spectra exhibited an average transmittance of 80% in the 300 to 2000 nm wavelength range. Also, from XRD, it was observed that the lattice shrinks and from transmittance that the bandgap energy increases with T . The Raman spectra exhibit 461 cm -1 assigned to F 2g mode of the fluorite cubic structure, where F 2g hardens when T increases as an effect of the shrinkage of the lattice.