CRYSTALLIZATION OF SOL-GEL DERIVED GLASS-CERAMIC POWDERS IN THE CAO-MGO-AL2O3SIO2 SYSTEM .2. CORDIERITE

Samples in the cordierite primary crystallization field were prepared in the CaO-MgO-Al2O3-SiO2 quaternary system by sol-gel techniques, usi ng both polymeric and colloidal gels. Dried gels were characterized by infrared spectroscopy, thermal analysis and electron microscopy. The crystallization of gel-like glass from both kinds of gels, as a functi on of temperature was followed by X-ray diffraction. Cordierite was de tected as the only final crystalline phase, although some other crysta lline phases, different for each kind of gel, were observed in the pat hway reaction. The polymorphic modification of cordierite detected was pseudohexagonal, because no evidence of splitting was observed.