Preparation and Properties of MgO-Al₂O₃-SiO₂ Glass–Ceramics with Controllable Crystalline Phases

Abstract

MgO–Al2O3–SiO2 (MAS) glass–ceramics with controllable crystalline phases were successfully prepared using the melting method followed by heat treatment. The effects of the main components of glass on the crystallisation kinetics, nucleation, crystallisation and properties of glass–ceramics were investigated in detail. As the Al2O3 and MgO contents increase and SiO2 content decreases, the crystallisation peak temperature and activation energy of MAS glass decrease, while the crystal growth tends to follow a homogeneous nucleation crystallisation. The MAS glass nucleation temperature and time increase with higher concentrations of Al2O3 and MgO and with a lower SiO2 concentration. Mg2(Al4Si5O18) indialite and MgAl2O4 spinel precipitate simultaneously in the MAS glass after crystallisation; the relative proportion of crystalline phases is related to the composition and crystallisation temperature. A higher SiO2 content allows the formation of a dominant indialite phase, while higher MgO and Al2O3 contents promote the formation of a dominant spinel phase. The MAS glass ceramic with a greater indialite phase has good dielectric properties with a dielectric constant of 6.499 and dielectric loss of 0.0064, while that of a higher spinel phase possesses improved mechanical properties, with a Vickers hardness of 715 Hv and a bending strength of 244.9 MPa.

Keywords

• MAS glass–ceramics
• crystallisation kinetics
• nucleation
• crystallisation