The impact of Ta2O5 in multinucleating agents on chemically strengthened MgO–Al2O3–SiO2 transparent glass-ceramics

Abstract

MgO–Al₂O₃–SiO₂ (MAS) glass-ceramics are significant due to their excellent mechanical properties. However, most of these glass-ceramics are opaque and lack chemically strengthened capabilities. In this study, chemically strengthened transparent MAS glass-ceramics were successfully synthesized by employing SnO₂ + ZrO₂ + Ta₂O₅ as a multinucleating agent. Systematic investigation was conducted using differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscope (TEM), field emission scanning electron microscope (FE-SEM), Scattered Light Photoelastic Stress Meter (SLP), and Vickers hardness measurements. The results show that Ta₂O₅ exhibits a good nucleation effect. With the increase of Ta₂O₅ content from 0 mol% to 0.5 mol%, the exothermic peak temperature of the precipitated crystals decreased from 976.3°C to 937.6°C. The primary crystalline phases precipitated in the MAS system were MgAl₂O₄ (PDF#21-1152) and ZnAl₂O₄ (PDF#05-0669), with secondary phases including SnO₂ (PDF#46-1088), ZrO₂ (PDF#50-1089), and Ta₂O₅ (PDF#21-1198). TEM-tested interplanar spacing data and electron diffraction ring data further confirmed the presence of these crystalline phases. At 0.5 mol% Ta₂O₅ content, after crystallization at 920°C, the average grain size was approximately 40.34 nm, with 86.57% transmittance at 550 nm. The Vickers hardness of the parent glass increased from 6.68 GPa to 7.17 GPa after heat treatment at 920°C. Following 5 h of ion exchange, Vickers hardness increased to 7.97 GPa, with surface compressive stress (CS) of 150.29 MPa and depth of layer (DOL_zero) of 80.96 µm. After 24 h of ion exchange, Vickers hardness reached 8.16 GPa, with CS of 239.86 MPa and DOL_zero of 93.28 µm. The conclusions provide new insights for further study of the MAS system and broaden its application field such as in cover materials.