Phase evolution and mechanical properties in Li ₂ O–Al ₂ O ₃ –SiO ₂ glass‐ceramics: Influence of heat treatment parameters

Abstract Lithium aluminosilicate (Li 2 O–Al 2 O 3 –SiO 2 , LAS) glass‐ceramics are commercially established as protective covers for smartphones and personal electronic devices. However, quantitative relationships between heat treatment parameters, phase evolution, and optical–mechanical properties remain incompletely resolved. This work systematically maps the influence of nucleation (560–620°C/0.1–8 h) and crystal growth (700–800°C/0.1–4 h) heat treatment parameters on dual‐phase LiAlSi 4 O 10 /Li 2 Si 2 O 5 nanostructures in LAS glass‐ceramics. Rietveld refinement shows that the combination of 580°C/4 h nucleation and 740°C/1 h crystal growth steps achieves an equal volume phase ratio (1:1) and 86.1% total crystallized volume fraction, yielding balanced performance: 86.4% visible‐light transmittance, 106.2 GPa Young's modulus, 7.6 GPa Vickers hardness, and 1.03 MPa·m 1/2 indentation fracture toughness. Increasing the crystallization temperature to 800°C enhances toughness to 1.21 MPa·m 1/2 via β‐quartz solid solution formation but reduces visible transmittance to 11.4% as a result of grain coarsening (> 170 nm). Chemically strengthened surfaces reach a 219 MPa Na + compressive stress layer (5× that of pristine glass) through a double ion exchange process (first in mixed NaNO 3 /KNO 3 molten salt, then in pure KNO 3 molten salt at 450°C), though crystallized volume fraction > 80% confines stress layers to 110–135 µm. These quantified relationships establish fundamental phase evolution‐property linkages in LAS glass‐ceramics, advancing predictive control of optical–mechanical performance.