PREPARATION AND CHARACTERIZATION OF ZIRCONIUM-OXIDE COATINGS PREPARED FROM ZRCL2(OC2H5)2 BY THE SOL-GEL PROCESS

Transparent single-component ZrO2 coatings on soda-lime glass substrates have been successfully prepared by the sol-gel route using ZrCl2(OC2H5)2 as the starting material. Detailed studies were carried out of the whole process including the synthesis of the organometallic compounds, the hydrolysis-polymerization and the sintering process. The results showed that zirconium dichloride ethoxide is preferred over other zirconium alkoxides for its enhanced stability on storage and for the feasibility of controlling the hydrolysis, i.e. the hydrolysis temperature changes the ZrCl2 (OC2H5)2 precursor at a molecular level therefore modifying the whole hydrolysis-polymerization process. Infrared multiple internal reflection spectroscopy was used to monitor structural variation of the coatings during heat treatment and the results suggested the formation of SiOZr bonds between the coating films and the substrate. The results of X-ray diffraction and scanning electron microscopy showed that the ZrO2 coatings remained in the amorphous state up to 400° C, but on increasing the heat treatment temperature to around 500° C oriented tetragonal ZrO2 monocrystals were precipitated. It is shown that such coatings have excellent properties and are therefore of high technological interest.