Microstructural control of CaO–Al2O3–SiO2 glass-ceramics by the amounts of tungsten oxide and carbon added as nucleation agent sources

Microstructural control of CaO–Al2O3–SiO2 (CAS) glass-ceramics (GCs) bearing metastable CaAl2Si2O8, a layered crystal, from a parent glass having a single composition was achieved by increasing the amounts of WO3 and carbon used as sources of metallic W particle nucleation agents. The average crystal size increased from 9.3 to 49 µm when the amount of WO3 and carbon were increased fivefold in the preparation of CAS GCs. To investigate the effect of WO3 and carbon separately, glass cullet containing WO3 was mixed with glass batches containing carbon and then melted to form glass specimens with different amounts of WO3 and carbon. Upon crystallization of these glass specimens, the average crystal size increased from 9.0 µm to 43 or 49 µm when the amount of WO3 or carbon was increased fivefold, respectively. The results indicate that changing the amounts of WO3 and carbon is necessary to control the CAS GC microstructure.