GEL SYNTHESIS AND CRYSTALLIZATION OF SODIUM TETRAGERMANATE GLASS POWDERS

Sodium tetragermanate gel (Na2O.4GeO2) was synthesised by hydrolytic p olycondensation of germanium ethoxide with sodium ethoxide in alcoholi c medium. Crystallisation behaviour of the gel, examined by differenti al thermal analysis and x-ray diffraction, is reported and discussed. Sodium tetragermanate gel crystallises in two steps. In the primary tr ansformation, at about 575-degrees-C, metastable Na2Ge4O9 crystals are formed as the major crystalline phase with a small amount of Na4Ge9O2 0 crystals. In the second transformation at higher temperatures metast able Na2Ge4O9 are converted to the thermodynamically stable Na4Ge9O20. These results are compared with those of the conventionally prepared glass.