Preparation of Li2O-SiO2 gels and glasses by sol-gel methods

Abstract

Li2O—SiO2 geis with lithia contents from 5 to 40 mol% have been prepared by several sol-gel methods. Silicon ethoxide and silicon methoxide have been used as starting silicon compounds while different lithium alkoxides and lithium salts were tried as lithium carriers. Drying Control Chemical Additives (DCCAs) were also used. The gelling behavior and the state of the gels are reported for the different routes of preparation. Monolithic gels could be obtained by the use of tormamide as a DCCA but not with glycerol. Many samples were dried and annealed then to temperatures up to 600 °C. Onset and kind of crystallization were observed by x-ray diffraction. The structural development was investigated by 29Si NMR. Li2O-SiO2 gel glasses crystallize much more easily, compared to conventionally melted glasses. On the other hand, they can be prepared very purely due to the use of the special chemical starting compounds.