PREPARATION AND CRYSTALLIZATION OF ULTRAFINE LI2O-AL2O3SIO2 POWDERS

Ultrafine powders of Li2O-Al2O3-SiO2 (GAS) glass-ceramic were prepared by the sol-gel process using tetraethoxysilane, titanium butoxide, lithium, magnesium, aluminium (and zinc) inorganic salts as starting materials. The effect of pH on the sol-gel transition and particle sizes of the Li2O-Al2O3-SiO2 system was studied. The nucleation and crystallization process of LAS powders were also investigated by differential thermal analysis and X-ray diffraction. The results show that a surface nucleation process occurs for ultrafine LAS powders. The LAS glass-ceramics fabricated from ultrafine LAS powders have a low thermal expansion coefficient, alpha < 10 x 10(-7) degrees C.