Sol-gel preparation of GeO2-doped SiO2 glasses

Silica glasses doped with GeO2 in the range 10(-3)-10 mol% have been prepared by means of a new sot-gel recipe. Medium-density aerogels, shaped as discs or cylinders, have been obtained in an autoclave using ethanol as the supercritical fluid. The densification treatment has been performed under a controlled atmosphere, originating in samples in the centimetre range. Fewer than 5% of the aerogels were fractured and, overall, the chosen route is particularly convenient in terms of simplicity and time saving. The Ge content was checked by means of inductively coupled plasma mass spectroscopy and neutron activation analysis techniques. The glass structures have been characterized by means of Si-29 magic angle spinning nuclear magnetic resonance, density, thermal gravimetric and differential thermal analyses.