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

Abstract

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 65SiO2·35GeO2 and plenty of Ge, O and Si were all found in it. However, the separated phase is found in the coating of 60SiO2·40GeO2 and a large number of Ge and O. It is proved by the Raman scattering investigation that the separated phase in the coating of 60SiO2 ·40GeO2 is germanium dioxide. The congeries of hydrolystates of Cl3 GeCH2 CH2 COOH play the main role in the formation of the 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 65SiO2·35GeO2 and this coating is homogenous.