The ratio of the intensity of Tb 3+ fluorescence at 543 nm because of an electric dipole transition ( 5 D 4 – 7 F 5 ) relative to that at 437 nm due to a magnetic dipole transition ( 5 D 3 – 7 F 4 ) was determined to be proportional to the amount of metastable CaAl 2 Si 2 O 8 crystals precipitated in CaO–Al 2 O 3 –SiO 2 glass. The present results indicate that Tb 3+ luminescence can be used as a probe to evaluate the crystallization of glass.

Effect of carbon on the co-presence of metallic tungsten (W) as nucleation agents and Eu2+ ions as a probe for tracking crystallization in CaO–Al2O3–SiO2 (CAS) glass was demonstrated by efficient reduction method of Eu2+ and metallic W.