Tuning Crystallization Pathways via Phase Competition: Heat-Treatment-Induced Microstructural Evolution

Spinel-based glass-ceramics face challenges such as a narrow crystallization window for the target phase and the difficulty in suppressing the competitive LixAlxSi1−xO2 crystals. This study proposes a method to regulate the phase formation in ZnO-MgO-Al2O3-SiO2 glass by precisely controlling the heat treatment temperature. The microstructural evolution was analyzed by DSC, XRD, Raman spectroscopy, SEM, TEM, and XPS. The results indicate that the heat treatment at a nucleation temperature of 780 °C for 2 h and a crystallization temperature of 880 °C for 2 h effectively inhibits the precipitation of the LixAlxSi1−xO2 secondary phase, yielding a glass-ceramic with nano-sized MgAl2O4, ZnAl2O4 spinel as the primary crystalline phase. The obtained glass-ceramic exhibits excellent mechanical properties, including a Vickers hardness of 922.6 HV, a flexural strength of 384 MPa, and an elastic modulus of 113 GPa, while maintaining a high visible light transmittance of 84.3%. This work provides a clear processing window and theoretical basis for fabricating high-performance, highly transparent spinel-based glass-ceramics through tailored heat treatment.