Preparation and optical properties of transparent zirconia sol–gel materials

The optical properties of zirconia sol–gel glasses, prepared from zirconium butoxide with organic modifying agents using different ways of preparation are described. The gels obtained are characterized with UV/Vis/NIR reflectance and transmission spectroscopy between 220 nm and 2600 nm, X-ray diffraction, SEM microscopy and IR spectroscopy. The optical band gap of the amorphous gels depends on the presence of complex forming modifying agents such as acetic acid and acetylacetone and varies between 4.84 eV and 2.97 eV, respectively. Complex formation between zirconium and acetylacetone starts in the sol and is characterized by a strong peak in the UV region at about 285 nm which changes during gelation. It is shown that samples, prepared without protection agents (acetic acid or acetylacetone) display a typical granulated microstructure while gels, obtained by addition of organic additives display a flat and compact surface.