1992 Volume 100 Issue 1166 Pages 1245-1250
The influence of compositions of coating solutions (SiO2, 1Na2O⋅99SiO2) and of substrates (SiO2 glass, Na2O-CaO-SiO2 glass) on the formation of sol-gel derived coating were evaluated by a scratch test, X-ray photoelectron spectroscopy (XPS), Fourier transformation infrared spectroscopy (FT-IR), a porosity test, and ellipsometry measurements. Three types of samples were prepared; (a) SiO2 film coated on Na2O-CaO-SiO2 substrate, (b) SiO2 film coated on SiO2 substrate, and (c) 1Na2O⋅99SiO2 film coated on SiO2 substrate. The results of the scratch test showed that Na+ ions influenced strongly on the adhesion of the film to the substrates. The strength of the adhesion of (a) and (c) was larger than that of (b). The results of XPS analysis revealed that the Na+ ions contained in Na2O-CaO-SiO2 substrates diffused easily into the film below 200°C, and that those in 1Na2O⋅99SiO2 film did not diffuse into SiO2 substrate. In the samples (a) and (c), a large amount of Na+ ions existed at the interface, which enhanced the adhesion of the film. The results of FT-IR and the porosity test indicated that the structure of sol-gel derived films were very porous and contained high content of residual -OH groups at the early stage of heat treatment. Na+ ions accelerated the dehydration of Si-OH and accompanying decrease of the porosity of films.