Effect of the Cr2O3 and TiO2 as nucleating agents in SiO2-Al2O3-CaO-MgO glass-ceramic system

The nucleation agent is one of the most important factors in glass-ceramics as it can control either the crystallization temperature or the activation energy. In this study, we investigated the effect of two common nucleation agents, TiO2 and Cr2O3, in the SiO2-Al2O3-CaO-MgO system. To determine the effect of TiO2 and Cr2O3 on nucleation, we measured the crystallization temperature by differential scanning calorimetry (DSC) scanning. To determine the activation energy of nucleation, the DSC scanning was made for the selected samples at various speeds. Also, the crystallinity of the selected sample was evaluated from the scattering intensity in X-ray diffractometry. Using DSC scanning, we found that TiO2 was effective in decreasing the crystallization temperature, while Cr2O3 was effective in decreasing the activation energy. We also performed nucleation heat treatment near the glass transition point. It is found that nucleation heat treatment was not effective in decreasing the crystallization temperature in our experimental condition. The XRD scattering method results showed that temperature is the key factor in crystallization and the effect of time is not as important.