We studied the spontaneous crystallization behavior for 60.5SiO2-2.5Al2O3-3P2O5- 18Na2O-16RMgO-16(1-R)CaO system glasses during cooling of melts through changing the relative content of alkaline-earth oxides. Such compositional variation leads to the formation of different crystalline phases, as well as different degree of crystallization, with the help of X-ray diffraction (XRD), heat capacity (Cp) and scanning electron microscopy (SEM). It is found that the obtained glasses are opalescent due to formation of orthorhombic NaCaPO4 during cooling when R≤0.5, and the degree of crystallization increases with substituting MgO for CaO. On the other hand, the spontaneous crystallized phases is hexagonal NaCaPO4 for R=0.75 and is Na2MgSiO4 for R=1.0, respectively, and besides, the appearance become transparent.
