Effect of CaO/La2O3 on Crystallization Behavior and Properties of Li2O-Al2O3-SiO2 Glass Ceramics

Composition design is critical for high-performance transparent LAS glass ceramics. This study investigated the effects of heat treatment temperature and CaO/La2O3 ratio at a fixed modifier content on crystallization behavior, network structure, microstructure, and comprehensive properties of LAS glass ceramics. Base glasses with different CaO/La2O3 ratios at a fixed modifier content were prepared by melt quenching and subjected to two-step nucleation–crystallization treatment at 700~900 °C. XRD and FTIR analyses revealed that β-quartz solid solution initially precipitated at 700 °C, followed by the formation of petalite and Li2Si2O5 at 750~800 °C, whereas β-spodumene and wollastonite emerged at 850 °C. Increasing temperature promoted crystallization, grain growth, and densification up to 850 °C, while excessive heating resulted in grain coarsening and slight property deterioration. Increasing La2O3 content refined the grains and improved density, hardness, and visible light transmittance. In contrast, higher CaO content enhanced network depolymerization, ion migration, and wollastonite precipitation. The C4L6 composition exhibited the best overall performance, achieving a bending strength of approximately 160 MPa at 800 °C and the lowest thermal expansion coefficient of 3.64 × 10−6 K−1 up to 300 °C, demonstrating an optimal balance among crystallization, microstructural refinement, and phase composition.