The structure of sodium aluminosilicate gels of various composition, prepared by sol-gel methods using TEOS and nitrates, was studied with Raman spectroscopy. Some of these gels, 12.5Na2O12.5Al2O375SiO2(albite) and 7.5Na2O7.5Al2O385SiO2, can be easily densified into glasses by heat treating them at 1100°C. The similarity between Raman spectra of the gel-derived and melt-derived glasses, in particular the absence of the non-bridging-oxygen peak at 1095 cm-1, shows that for the albite composition the structure consists of a 3D-network of interconnected AlO4/SiO4tetrahedra with the negative charge of the AlO4groups compensated by the sodium ions. The network structure of the glass phase is already present in the gel phase at temperatures as low as 500°C. For other compositions, such as 15.5Na2O15.5Al2O369SiO2, densification of the gel into a glass is not possible because of crystallization during the heat treatment. © 1991.
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