Sol-gel Processing and Crystallization of Lithium Tetragermanate

Lithium tetragermanate gel was synthesized by hydrolitic polycondensation of germanium ethoxide with lithium hydroxide monohydrate in alcoholic medium. Crystallization behaviour of the gel, examined by differential thermal analysis and X-ray diffraction, is reported and discussed. Lithium tetragermanate gel crystallizes in two steps. In the primary transformation, at about 560-degrees-C, microcrystallites of Li2Ge4O9 and GeO2 are crystallized in an amorphous matrix. In the second transformation, at about 600-degrees-C, well shaped Li2Ge4O9 and Li2Ge7O15 are formed. The values of activation energy for the two stages are found to be 557 and 405 kJ mol-1, respectively. Activation energies are comparable with those reported with conventional melt glasses from oxides