CRYSTALLIZATION OF SOL-GEL-DERIVED GLASS-CERAMIC POWDERS IN THE CAO-MGO-AL2O3-SIO2 SYSTEM

Samples in the anorthite primary crystallization field were prepared i n the CaO-MgO-Al2O3-SiO2 quaternary system by sol-gel techniques. The homogeneous dried gels were characterized by infrared spectroscopy, th ermal analysis and electron microscopy, The crystallization of gel-lik e glass as a function of temperature was followed by X-ray diffraction . Anorthite was detected as the only crystalline phase. Thermal analys is results indicated a mechanism of crystal growth dominated by surfac e nucleation. This fact could be related to the small size of the prim ary particles observed by electron microscopy.