Crystallization kinetics, structural and mechanical properties of transparent lithium aluminosilicate glass-ceramics

Transparent glass-ceramic in the SiO2-Li2O-Na2O-Al2O3-BaO-P2O5-ZrO2 system were prepared by the three-stage heat treatment process. The effects of Al2O3 content on the crystallization behavior, microstructure, and physical properties of the glass-ceramics were investigated by differential scanning calorimeter (DSC), X-Ray Diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscope (SEM). As the Al2O3 increases from 4 to 7 mol%, all the Al3+ ions are present in the [AlO4] tetrahedra and participate in the glass network, resulting in the more compact structure of glass. The increasing in the glass network connectivity leads to the higher crystallization activation energy, hindering the formation of lithium disilicate and promoting the precipitation of Al-containing crystalline phases. The main crystalline phase of glass-ceramics transform from lithium disilicate and petalite to LixAlxSi1-xO2, and the transmittance of glass-ceramics decrease. Upon the three-steps heat treatments of 540°C/4h + 610°C/2h + 730°C/4h, the glass-ceramic with 4 mol% Al2O3 containing petalite and lithium disilicate crystals shows high transparency of ∼85% in the visible light range, high hardness 8.07 GPa, and fracture toughness of 1.37 MPa·m1/2, which shows great potential in the applications of protective material for mobile devices.