Effect of isothermal treatment on the structural, microstructure, and physio-mechanical properties of Li 2 O-Al 2 O 3 -SiO 2 glass–ceramic

This work aims to investigate the effects of isothermal treatment on the structural, microstructure, and physio-mechanical properties of Li 2 O-Al 2 O 3 -SiO 2 (lithium aluminosilicate (LAS)) glass–ceramics. The different sintering temperatures affected the final crystalline phase formation leading to a variation of LAS glass–ceramic properties. This work also aims to achieve the most stable crystalline phase at high temperature in LAS glass–ceramics which is β-spodumene (LiAlSi 2 O 6 ) with improved density, lower porosity, and higher flexural strength. The LAS was isothermally sintered at elevated temperatures of 900 to 1200 °C for 30 min. The X-ray diffraction (XRD) results showed the complete transformation of β-spodumene from β-quartz occurred at 1000 °C. However, the sintering temperature did not change the crystalline phase when sintered above 1000 °C, but the lattice parameter of the crystal structure was slightly altered. It was observed that the LAS glass–ceramic grain size, density, and flexural strength increased with temperature. The smallest mean grain size of 0.61 µm for LAS glass–ceramic sintered at 1100 °C implied the increased flexural strength of LAS glass–ceramic at 146.25 MPa which is also influenced by the full densification at 2.46 g/cm 3 with less porosity. The isothermal treatment indicated that sintering at 1100 °C provided a denser, less porous, smaller mean grain size and higher flexural strength LAS glass–ceramics which is preferred for thermal shock resistance applications.