Surface and Morphological Features of ZrO₂ Sol-Gel Coatings Obtained by Polymer Modified Solution

Thin, homogeneous ZrO₂ films were obtained by spin coating method from ZrOCl₂.8H₂O solution, modified with polyethylene glycol (PEG, Mw = 400). The films have thickness of 80 nm and refractive index of about 1.45, which varied with the amount of added PEG. The thermal behaviour of the precursor was studied with thermogravimetry and differential thermal analysis (TG-DTA). The X-ray diffraction (XRD) analysis revealed the presence of a mixture of monoclinic and tetragonal ZrO₂ polycrystalline phases with nanosized crystallites. The formation of hydrogen bonds among the organic and inorganic components was proved by means of fourier transform infrared spectroscopy (FT-IR) analysis, while the different defect centers were investigated with electron paramagnetic resonance (EPR) spectroscopy. The scanning electron microscopy (SEM) images showed that the samples are dense, crack free with ganglia-like nanostructure. It was established that the addition of polymer resulted in the introduction of free volume in the films, which also varied with the content of PEG in the precursor solution.