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

Abstract

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.