MgO-doping in the Li2O–ZnO–Al2O3–SiO2 glass-ceramics for better sealing with steel

• We selected the bivalent Mg2 + to substitute Al3 + and designed five compositions.
• Glass-ceramics were characterized by Vickers hardness, bending strength and TEC.
• The addition of Mg2 + can give LZAS glass-ceramic a finer & smooth microstructure.
• Mg2 + greatly improved the mechanical and thermal properties of LZAS glass-ceramics.
• The resulted glass-ceramic was ideal for sealing with steel.

Effect of Al2O3 substitution by different amounts of MgO on crystallization and various properties of Li2O–ZnO–Al2O3–SiO2 glass-ceramics were investigated. With the increase of MgO content, the glass transition temperature (Tg) changed slightly, while the crystallization temperature (Tc1, or Tc2) decreased greatly, which may be related with the effect of Mg2 + ion on the glass structure based on the Fourier transformed infrared spectra (FTIR) analysis. MgO did affect the crystallinity and grain size of glass-ceramics according to scanning electron microscope (SEM) results. The Vickers hardness, bending strength and average thermal coefficient of the glass-ceramics were greatly affected by the MgO content. The best combination: 7.96 GPa, 150 MPa and 110 × 10− 7 °C− 1 was achieved by crystallizing the sample with 9 wt.% MgO content at 750 °C for 2 h, which are suitable for sealing with steel (about 120–130 × 10− 7 °C− 1, 20–400 °C).