Nucleation behavior of Na2O–SiO2 glasses with small amount of additive

Nucleation in 49Na2O · 49SiO2 · 2ZrO2 and 47Na2O · 51SiO2 · 2ZrO2 glasses were investigated by differential thermal analysis measurement after heat-treatments at 400–580°C for 0–123 h. The addition of ZrO2 increased crystallization peak temperature, TC, and shifted the temperature, Tmax, at which nucleation rate is maximum to higher temperatures. The relationship between the number density of nuclei formed during the heat-treatment and TC was calculated. The variation of the number density of nuclei was obtained from the comparison between the calculated TC and the observed TC as a function of heat-treating time. The transient time for nucleation of 47Na2O · 51SiO2 · 2ZrO2 glass was 42 h at 430°C. From these results, we found ZrO2 has an effect on the nucleation kinetics of Na2O–SiO2 glass.