Effects of Na₂O and CaCl₂ on the Crystallization and Mechanical Properties of CaO-MgO-Al₂O₃-SiO₂ Glass–Ceramics

In this paper, we respectively added 5 wt% of Na₂O and CaCl₂ to the CaO–MgO–Al₂O₃–SiO₂ base glass, aiming to analyze the effect of the types of flux, CaCl₂, and traditional flux Na₂O, on the crystallization behavior and mechanical properties of the sintered glass–ceramics. Besides, 1 wt% of Cr₂O₃ was added as the nucleating agent to form the Cr-spinel nucleus and promote the bulk crystallization. The CaCl₂-bearing glass–ceramics (GC-Cl) showed lower porosity and crystallinity compared with the Na₂O-bearing glass–ceramics (GC-Na). After sintering at 950 °C for 1 h, the bending strength, Vickers hardness, and fracture toughness of GC-Cl were 163 MPa, 6.9 GPa, and 2.4 MPa·m^1/2, respectively, while they are 191 MPa, 8.2 GPa, and 2.3 MPa·m^1/2 for the GC-Na. Although the bending strength and hardness of GC-Cl are lower than that of GC-Na, adding CaCl₂ as a flux may provide a route for the comprehensive utilization of CaCl₂-bearing wastes.