Effect of B2O3 on the crystallization, structure and properties of MgO–Al2O3–SiO2 glass-ceramics

Abstract

The formation of α-cordierite glass-ceramics in the MgO–Al2O3–SiO2 system without and with addition of B2O3 was investigated. Moreover, the effects of different contents of B2O3 on the crystallization behavior, structure variation, thermal and physical properties of glass-ceramics were studied, and the action mechanism of B2O3 was systematically discussed by XRD, FT-IR and XPS. The results show that a proper amount of B2O3 shortens the crystallization route and reduces formation temperature of α-cordierite, which further promotes the direct precipitation of α-cordierite in MAS system. The glass-ceramics undergo the phase transitions from intermediate phases of MgO·Al2O3·SiO2 and Mg0·6Al1·2Si1·8O6 to pure α-cordierite without the addition of B2O3. However, the pure α-cordierite directly precipitates in the glass-ceramics adding 4 mol% B2O3 without intermediate phases. Low B2O3 content (4 mol%) promotes the crystallization of α-cordierite, while high B2O3 content (8–12 mol%) inhibits it, which is accompanied by the increase of thermal expansion coefficient from 1.70 × 10−6 °C−1 to 3.72 × 10−6 °C−1 and the decrease of Vickers hardness from 9.4 GPa to 6.9 GPa. B2O3 is confirmed to be very important in controlling the crystallization process of α-cordierite in this glass-ceramics system, and this study is helpful for providing the reference value for others to choose B2O3 and its content.