Effect of substituting Na2O with B2O3 on the crystallization and properties of MgO-Al2O3-SiO2 transparent glass-ceramics

ABS T R A C T MgO-Al2O3-SiO2 (MAS) transparent glass-ceramics were prepared with ZrO2 as a nucleating agent, and the substitution of B2O3 for Na2O on the properties of the MAS glass-ceramics was investigated systematically. The results show that the substitution of B2O3 increased the glass transition temperature, crystallization temperature, and crystallization activation energy. Additionally, there was no change in the main crystal phase of the glass-ceramics, which were ZrO2 (JCPDS PDF#.50-1089) and Al0.52Zr0.48O1.74 (JCPDS PDF#.53-0294). The crystal growth mode shifted from three-dimensional growth to two-dimensional growth, and the crystal morphology transformed from a spherical appearance to a star-shaped appearance. Moreover, the mechanisms of the property changes induced by B2O3 substitution are revealed and discussed. The transmittance of MAS glass-ceramics without B2O3 decreased from 88 % to 32 % as the crystallization temperature increased from 800 degrees C to 920 degrees C, and decreased from 90 % to 8 % when B2O3 was added. Additionally, the Vickers hardness of MAS glass-ceramics decreased from 6.37 GPa to 6.13 GPa, after the introduction of B2O3, while, the fracture toughness increased from 1.48 MPa m1/2 to 1.55 MPa m1/2. The scratch behaviour of glass-ceramics exhibits a negative correlation with the applied load, but a positive correlation with the crystallization temperature. In particular, the incorporation of B2O3 substantially enhances the scratch resistance of glass-ceramics. The conclusions pro -vide researchers with the roles of B2O3 in crystallization kinetics, microstructure, transmittance, and mechanical properties of MAS transparent glass-ceramics for various applications such as covers.