ZrO2 and Cu/ZrO2 sol-gel materials spectroscopic characterization

Copper-doped zirconia (1% mol) and zirconia powders were prepared by the sol-gel process, using zirconium n-butoxide and copper nitrate as precursors. The resulting xerogels are nanocrystalline and exhibit different properties from the corresponding microcrystalline materials. The copper nitrate salt was dissolved and co-gelled in situ at the initial stage of the reaction. The properties of the resulting materials were studied by XRD, FTIR and UV-Vis. The as-prepared samples were amorphous and crystallized to the tetragonal zirconia phase at 400 degrees C. At temperatures higher than 600 degrees C, the monoclinic phase was also obtained. No evidence of discrete crystalline copper compounds was observed, consistent with good dispersion of the dopant. Several bands were observed by FTIR in the 4400-3000 cm(-1) region, which diminishes in intensity and shifted to higher wavenumbers with heating. The bandgap energy (E-g) was strongly modulated by the presence of the dopant and heating temperature, with increasing temperature leading to a corresponding decrease in E-g.