CRYSTALLIZATION OF CALCIUM ZINC ALUMINOSILICATE GLASSES

The crystallization behaviour of some glasses in the CaO-ZnO-Al(2)O(3)-SiO(2), system was investigated using different heat-treatment parameters. Cr(2)O(3) and CaF(2) were used as nucleating agents. Differential thermal analysis, X-ray diffraction, dilatometry and scanning electron microscopy were used in this study. Melilite, alpha- and beta-willemile, anorthite, wollastonite, pseudowollastonite and petedunnite phases developed in the investigated glasses. The formation of compatible and incompatible phase assemblages and the effect of Cr(2)O(3) and CaF(2) are illustrated. Glass-ceramics with fine-grained microstructures and CTE values ranging from 36 to 73 x 10(-7) K(-1) in the 20-700 degrees C range were obtained.