Liu Aiyun

IR spectra analysis of SiO2−TiO2−GeO2 gel glass of CO2 laser transmitting hollow waveguide

Both titanium and germanium were introduced into silicon dioxide system by sol-gel method to move its region of anomalous dispersion caused by IR resonance absorption towards the wavelength of CO2 laser. It is indicated by IR absorption spectra that as the content of SiO2 decreases in this glass system TiO2 and GeO2 tends to exist in their own phases. As for the gel glass with a composition of 40 SiO2·30TiO2·30GeO2, when the temperature is below 600°C, germanium atoms exist mainly in Ge−O−Ge bonds. With the temperature increasing from 800°C to 1000°C, titanium atoms in Si−O−Ti bonds abmost transform into Ti−O−Ti bonds. Furthermore, a large number of Si−O−Ti and Si−O−Ge bonds formed when the temperature approaches 800°C, which makes a notable IR absorption band round the wavelength of CO2 laser. Therefore, sol-gel based SiO2−TiO2−GeO2 gel glass is a candidate material for CO2 laser hollow waveguide.

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 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.