Crystal nucleation rates in a Na2O–SiO2 glass

Nucleation of sodium metasilicate crystals in sodium silicate glass of composition 43Na2O–57SiO2 is investigated. Two-stage isothermal heating and optical microscopy techniques are utilized to determine the steady-state nucleation rates at temperatures between 390°C and 455°C. The results of this investigation are compared to the results we obtained for the temperature dependence of the nucleation rate in these glasses via a DTA technique which we presented in a previous study. It is found that the results of the two techniques are in agreement within experimental error. It is observed that the peak nucleation rate for this composition occurs near 410°C, which is about 50°C lower than that reported for nucleation in the 46Na2O–54SiO2 glass composition.