Fabrication and microstructure of SiO₂-GeO₂ sol-gel glass coatings

SiO₂-GeO₂ sols and gel glass coatings with different contents of germanium dioxide were fabricated. Stable and transparent sols could only be obtained when the content of GeO₂ was under 35%. It is shown by SEM that only one continuous phase is observed in the coating of 65 SiO₂·35 GeO₂ and plenty of Ge, O and Si were all found in it. However, the separated phase is found in the coating of 60 SiO₂·40GeO₂ and a large number of Ge and O. It is proved by the Roman scattering investigation that the separated phase in the coating of 60SiO₂·40 GeO₂ is germanium dioxide. The congeries of hydrolystates of Cl₃GeCH₂CH₂ COOH play the main role in the formation of separated phase when the proportion of GeO₂ is much higher. Si-O-Ge, Si-O-Si, and Ge-O-Ge bonds form in the coating of 65 SiO₂ ·35 GeO₂ and this coating is homogenous.